PROTOZOAN CATTLE FEVER. TEXAS FEVER. PALUDISM OF CATTLE.
Symptoms. Definition: protozoan, tick-borne, febrile, affection, of wild damp lands, and warm seasons, with enlarged spleen and liver and hæmolysis. Historic Notes; Old World; Australia; tropical and subtropical America. Causes: contact of cattle from salubrious districts with the insalubrious or with cattle from such; Piroplasma bigeminum; a bovine parasite, reducing red globules by ¾ths.; successive forms of piroplasma; the cattle tick, boöphilus bovis, bearer of piroplasma; demonstration of the tick agency; toxic saliva of tick; toxic property in blood; question of identity of infection-bearing ticks. Lesions: putrefaction rapid, icterus, ticks, blood oozing in skin, hydræmia, hæmoglobinæmia, few red globules, small petechiæ, slight serous exudates and effusions: congestion, petechiation, sloughing, perforation of gastric mucosa, congestion of intestinal mucosa, in rectum like port wine; liver enlarged, congested, biliary radicles in acini gorged with bile; spleen enlarged, engorged; kidneys œdematous, blood-stained; bladder petechiated; urine opaque or red, in convalescence watery; womb; fœtus. Incubation three to ten days; delays due to hatching of ticks. Symptoms: Acute case: anamnesis; hot season; hyperthermia 104° to 109° F.; hurried breathing and pulse; anorexia; dulness; costiveness; icterus; prostration; weakness; delirium; urine turbid, red; blood hydræmic; diarrhœa; emaciation. Duration one to seven days. Fatal (90%) to exotic cattle; mild in indigenous, or cool season. Mild case; temperature 103°, anorexia, dulness, costiveness, enuresis, albuminuria, pallid mucosæ, emaciation, round protozoön in globules, ticks, oligocythemia. Differential diagnosis, from anthrax. Treatment: laxative; antiseptic; mucilaginous food; picking off ticks; anti-ixodic lotion; tick-free pasture or place. Prevention: destruction of ticks; picking; dipping or smearing with tick killing preparation, paraffin or extradynamo oil and sulphur, danger with shipping; dressing of all cattle at intervals during warm season; cultivation of tick-infected land; exclusion of cattle for one summer and two winters; soil cattle for three weeks in each of two tick free pens, to let ticks drop; danger of nonimmunized cattle in infested area; suggestions for extinction by States. Immunization: Infection of sucking calf; infecting by a few ticks: by graduated injections of piroplasma blood; technique; injection of blood from body of tick. Limited value of artificial tolerance. Marketing of the beef. Federal restrictions.
Synonyms. Splenic fever; Spanish fever; Mexican fever; Southern cattle fever; Australian tick fever; Tristeza; Red water; Black water; Bovine periodic fever; Bovine yellow fever; Maladie du bois; Holzkrankheit; Moor evil; Wood-ill; Ixodic Anæmia; Roumanian hæmoglobinuria.
Definition. A specific fever of cattle, enzoötic during the warm seasons in the low, malarious grounds and wooded or uncultivated districts of different countries, caused by a protozoön in the blood and red globules, which is conveyed from animal to animal by ticks, and leading to engorgement of the spleen and liver, destruction of the red globules, hæmoglobinuria, and oligocythemia.
Historic Notes. This malady has doubtless existed from time immemorial in different malarial districts of the Old World, where the wood and moor ill is now coming to be recognized as a protozoan tick-borne disease. The malady exists in Roumania (Starcovici, Babes, Gavrilescu), Turkey (Nicolle, Adil-Bey), Sardinia (San Felici, Loi), Southern France (Lignieres), Italy (Celli, Santori), Algiers, Tunis (Lignieres), Finland (Krogins, Von Hollens), West Indies, Mexico, Nicaragua, United States of Columbia, South America as far south as the Argentine Republic, German East Africa (Koch), Transvaal (Theiler), S. Australia (Pound). In Australia imported European cattle found the infection waiting for them in the uncultivated bottoms. In America it doubtless prevailed on the seaboard and islands of the Gulf of Mexico from the time of the importation of Spanish cattle, but for the first definite account of it we are indebted to Dr. James Pease, who records the widespread destruction of the native herds in Lancaster, Co., Penn., in connection with the introduction of cattle from the south. None of the southern cattle died, but wherever they traveled, the native stock perished all but universally. Other droves from South Carolina were equally destructive to all cattle along their track. The recorded symptoms of anorexia, great weakness, often inability to stand, trembling, groaning, bloody urine, bleeding from the nose, costiveness, congested kidneys, and decomposed, incoagulable blood serve to identify the disease.
Later, whenever southern cattle were moved north, the disease followed their trail. Florida cattle left infection along their route until they reached the border of Virginia, where it usually ceased. When taken from the Georgia mountains to the lowlands, they died without infecting the native stock, and, when such native stock of the lowlands were moved to the hills or the north, they conveyed the fever to the stock among which they came, though themselves well and improving all the time (Wilkinson). Similar experiences were had in all the middle states up to the war of 1861, but, in too many cases, the real source of infection was overlooked. It was observed that the disease was confined to the vicinity of the main highways and drove roads running north, and spared the lands lying somewhat back of these routes. Attention was drawn to the Texas cattle in 1853 when a herd of 450 which had wintered in Jasper Co., Mo. moved north passing through Vernon Co. in June, and causing losses of 50 to 90 per cent. of the native cattle along their course, and only along that line. Such invasions occurred yearly, and in 1858 $200,000 worth of native cattle perished from this cause in Vernon Co. alone (A. Badger). During the war (1861–64) the cattle, in Texas especially, encreased without meeting with an adequate market, and, on the opening of the trade once more, they were sent north in large numbers carrying infection with them. When Forts Smith and Gibson had been occupied by the Union soldiers, the southern cattle poured in along the military road and the Kansas farmers along this route suffered severe losses, as well as those to whom the southern cattle were finally distributed (Bray).
Causes. Up to 1889 the true cause of Texas fever was unknown. It was well established that cattle brought from the lowlands of the southern states, during the warm season, though themselves in apparently the best of health, proved deadly to northern cattle with which they came in contact, to those that followed them in the same pasture during the same warm season, and even in many cases to the mountain cattle of the south. In the same way northern cattle, removed to the infected regions in the south, contracted the fever and almost all perished. This was equally true of cattle taken from the northern states to Jamaica or other islands in the Gulf. In the winter season, after the first severe frosts of autumn and before the last keen frosts of spring, the southern cattle could be safely introduced into the northern states and on this a modus vivendi, for a trade in southern cattle in the winter only, was based.
Microbiology. Piroplasma bigeminum: Apiosoma bigeminum. (Apios pear, geminus twin). In 1888 Starcovici discovered pyriform organisms (Babesia bigeminum) in the red blood globules of Roumanian cattle suffering from hæmoglobinuria, and Babes, after a study of the organisms, named them Hœmatococcus. The following year Theobald Smith found them in the Texas fever blood, and recognized them as protozoa (Pirosoma bigeminum). Wadoleck proposed Apiosoma, Bonome Amœbosporidia, and Patton, Piroplasma. The latter pointed out that Pirosoma was already in use for another organism. Th. Smith’s discovery identified Texas fever with the Roumanian hæmoglobinuria, and stimulated the Bureau of Animal Industry to an extended research which, in the main, elucidated the true nature of the disease. In a long series of experiments the observers produced the disease in healthy susceptible cattle, by injecting them, in the warm season with the blood of sick animals, and as constantly failed in the experimental inoculation of similar blood on non-bovine animals such as sheep, rabbits, Guinea pigs and pigeons. In Australia, Pound had violent fever in two injected sheep but no pyroplasma, and their blood injected on the ox, had no effect. In none of these latter were the blood globules invaded by the parasite, nor were the corpuscles lessened in number. In the affected cattle, the red cells were reduced from the normal 7,000,000 per cubic mm. to 1,800,000 and even lower in some cases.
The Piroplasma Bigeminum passes through a series of forms in the blood. Theobald Smith found in the red globule and attached to its margin a pale round body 0.5μ in diameter, and staining freely in alkaline methylene blue and other basic anilin dyes and in hæmatoxylin, but not in acid coloring fluids. These he found in the red globules in acute cases, often in company with the pear-shaped bodies, and usually in the absence of the piriform bodies in chronic cases, in non-fatal relapses, in cases occurring in cooler weather, (late autumn or early winter) and in immune southern cattle. The red cells containing these rounded organisms were not crenated nor distorted, though 50 per cent. of them might contain the parasite. He looked on these as the earlier stage of the organism which later developed into the piriform body, by segmentation of its substance. The piriform or spindle-shaped bodies were usually found in pairs connected at their pointed ends by a filament and extending across nearly the whole breadth of the red globule. Free microörganisms, pear-shaped or round, he failed to find in the blood of the large vessels, but saw them only in the cardiac capillaries and especially in the kidneys. In some cases the dim remnant of the disintegrated blood globule could still be detected around the parasite.
Laveran and Nicolle, examining the blood of Italian cases by fixing and staining, found the two forms, round or oval, and piriform, and claimed that the first passed into the second by segmentation.
Lignieres working in Buenos Ayres with the most ample opportunity as regards fresh material and authority to use it, watched the successive changes in the living organisms, and reached further conclusions. He diluted the blood with a 7 per cent. salt solution, or with ox serum or both, until the globules stood apart in the field. The blood can be kept under observation for days under a cover glass luted with sterile paraffin, and the changes clearly traced. Securing the blood from a subject having a great abundance of infected globules (usually at the height of the hæmoglobinuria) he found mainly the piriform parasite intraglobular and free, and in the latter an active whirling motion was kept up by means of the flagellum at its pointed end. As usually arranged in pairs (gemina), whether inside or outside the globule, they are connected by the flagellum attached to their pointed ends. Careful observation enables one to detect in the pyriform mass a small brightly refrangent point like a nucleus. In this form the piroplasma is 3 to 4μ in length.
After 4 or 5 hours, and on toward the 8th, the piroplasma has assumed the round or oval form with a small linear prolongation (flagellum) and shrunken to 1 to 1½μ in diameter. All the piriform bodies pass into the rounded so that this last is the second stage of their development and not the first as was formerly supposed. The round forms are always present in great numbers in the cortex of the kidney in the second stage of the disease (toward the subsidence of the hæmoglobinuria). The refrangent nucleus is no longer to be seen.
After, one, two or more days there appears in the round parasite a chromatine mass, which breaks up into 2, 3, 4 or 5 smaller chromatic bodies, which Lignieres considers as germs. He has seen no division of the protoplasm, but on the contrary the germs escape, yet remain for a time attached to the outer surface of the parent organism. They show rapid jerking movements.
Lignieres claims to have followed all these changes in the blood kept in a sterilized glass cup at room temperature or in the thermostat, and in the stomach of the tick, as well as on the warm stage of the microscope.
He claims to have made a further success in cultivating the parasite in ox-blood serum highly charged with hæmoglobin. It was only occasionally, and by the use of blood extraordinarily rich in the parasites, that success was obtained. In one such case he produced five successive cultures, the product being the rounded forms only and within these the germs. There were no piriform bodies. These are not formed outside of the red globules. The third successive culture in this medium grew with great readiness, producing larger parasites with less disposition to contract, but the fourth and fifth cultures were encreasingly poor. Inoculation with these cultures failed to produce the disease. To explain this the doctrine of passive germs, strong for survival, but weak pathogenically, is hazarded.
To summarize, the successive stages of the piroplasma are: 1st. The intraglobular pear-shaped bodies, with flagellum often connecting two bodies. 2nd. The rounded bodies with refrangent nucleus—intraglobular or extraglobular. 3d. The free round bodies with the nucleus divided into 2 to 5 chromatin masses. 4th. The free chromatin masses, large, active, infecting germs, and small, passive, noninfecting germs. The insuccess of inoculations of cattle with the last-named bodies throws an air of doubt upon them as links in the pathogenic chain. Definite information on the antecedents, environment, food, etc., of the cattle unsuccessfully inoculated, including the season, shelter and meteorological conditions might have brought us a step nearer to the full life history of the piroplasma.
The Cattle Tick: Boöphilus Bovis: Ixodes Bovis: I. Dugesii: The Invertebrate Host of the Texas Fever Organism. As early as 1868 shrewd observers had noticed that in all outbreaks of Texas fever the affected animals were covered with ticks, and drew the natural inference that the disease was due to the bites of these insects. But the prevalence of ticks in localities where the disease was unknown served to draw attention away from the important fact that was suggestive of the true explanation of the disease. The truth, however, constantly obtruded itself that casual cases were never found in the absence of the tick. Finally, in 1889, Kilborne conceived the idea of putting the matter to the test, and with the approval of the Chief of the Bureau of Animal Industry, set aside special paddocks for this purpose. Five native cattle were placed, at midsummer, with three South Carolina cattle, from which all ticks had been carefully picked, and they completely escaped infection.
After seventy-one days, on September 6th, when the hottest weather had passed, two were turned into a lot with four South Carolina cattle of the original herd which had stocked the pasture with ticks. Of the two one died of Texas fever, September 20th, and the other sickened in the last week of September, and had a relapse in October, but finally recovered. Of eleven other native cattle placed in this tick-infested field up to September 30th, ten sickened and one escaped. One animal placed in the field October 19th escaped.
Again three North Carolina cattle and three natives were placed in a field September 14th and 15th. The new generation of ticks was retarded by the cool season, so that few larvæ appeared on the native stock yet one of the three sickened.
These results were confirmed by a series of other similar experiments.
In a further experiment, September 13th, thousands of ticks, mostly mature, from North Carolina, were scattered over a second lot and four native cattle turned into it next day. Three sickened and one, to outward appearance, escaped.
These results were corroborated by experiments made in succeeding years. In addition the disease was produced regularly in native stock by placing on their skin the six-legged larvæ of boöphilus bovis, which had been hatched in glass vessels in the laboratory. It was also shown that the Washington winter destroyed the ticks in infected pastures so that native cattle could be safely turned on them the following spring or summer.
To summarize:—
1. The blood of southern cattle containing the piroplasma produced the disease when injected into a healthy susceptible animal.
2. The animal with piroplasma in its blood, did not convey the disease, in the absence of ticks, to a susceptible animal kept with it.
3. The animal with piroplasma in its blood and covered with ticks conveyed the disease to a susceptible animal kept with it.
4. The ticks hatched and raised in glass vessels in the laboratory, when put on susceptible animals, infected them.
5. Ticks taken from cattle harboring the piroplasma, and put on the skin of susceptible animals, or on their pastures in the warm season, infected the exposed stock.
6. The six-legged larvæ developed in the laboratory from the eggs of mature ticks, taken from cattle having the piroplasma, conveyed the disease.
7. On bare pastures as far south as Washington the winter frosts destroyed the ticks so as to render the pastures safe on the following season.
8. Ticks artificially raised in a warm laboratory, produced the disease when placed on susceptible cattle in a warmed stable (65° to 80° F.) in winter.
9. In the Gulf states, in stables which the cattle occupy constantly or enter twice daily for milking or feeding, the ticks may live through the entire winter. The same has occurred in the warm swill stables in the north.
10. When taken into a new locality, it is rarely the mature ovigerous ticks that bite and infect the native cattle of the place, but the next generation of larvæ, so that time must be allowed for the laying and hatching of ova.
11. Ovipositing usually occupies about a week, while hatching varies with the temperature from two to six weeks.
12. Cases can be adduced in which native cattle followed, on the same pasture, the tick-bearing infecting cattle, and remained for a week or more, and yet escaped, the larvæ being as yet unhatched from the ova. Other native cattle, following these two or three weeks later, perished almost without exception.
13. This delay in the hatching may be indefinitely prolonged, and thus in the southern states, the winter may be tided over, without the loss of vitality in the ova, especially if it is covered by leaves, moss, wood, or decaying vegetable matter.
14. When dealing with lung plague in Chicago in 1888, I noted the facts that every cow that entered a city stable through the stock yards during the dry, hot, midsummer weather died of Texas fever within a month, while those that passed through the same yards during a particular rainy week, all escaped. Berkau has shown that, in the absence of the coating of the glutinous saliva, the eggs do not hatch, and here we may assume that this covering was washed off by the rains and the eggs perished.
15. It has long been noticed that the ticks are scarcely at all dangerous to young calves living on milk. This applies not only to calves born of cows native to infected localities, and therefore possibly having a congenital immunity, but also to the calves of northern and susceptible cows, and which were exposed simultaneously with their dams. It suggests a special defensive power in even the bovine system when sustained on animal food. In the Bureau of Animal Industry experiments, calves of four months, already using vegetable food freely, sickened but still, as a rule, recovered.
16. The Bureau fed three cattle with adult live ticks (2000 to one animal) but no infection resulted.
17. Four cattle were injected intravenously with the liquid charged by crushing ticks in a mortar with distilled water. In some cases the liquid was put through a Pasteur filter, in others only through two thicknesses of filter paper. No infection ensued.
18. Lignieres injected, subcutem, in different animals the pulp of the ticks at all stages of life, ground in a mortar with distilled water, but found in no case tristeza as the result nor any destruction of red globules.
The apparent paradox involved in the last three items probably finds its explanation in the statement of Nicolle and Adil-Bey that, in biting, the tick instils into the wound a venomous saliva which causes local congestion and infiltration and presumably operates on the blood globules as well. Curtice describes the two racemose glands situated under the head shield, the secretions of which are pressed out by the movements of the mouth ring and appendages. How much of this irritant and toxic action is inherent in the saliva, and how much due to the protozoan contained in it, has not been shown. Nicolle, Adil-Bey and, later, Lignieres showed a similar toxic property in the blood. Three to five cc. of blood taken from an acute case at the crisis and injected into the marginal vein of the ear in a rabbit, killed the subject in a few seconds. A similar amount thrown into the peritoneum of a Guinea pig destroyed life in a few minutes. It is probable that the dilution of the venom in the mass of tick pulp and distilled water reduced its toxic quality to such a low ebb that the red globules were comparatively unaffected by it and successfully resisted the attacks of the microbe.
The name Boöphilus bovis was given to the bearer of the Piroplasma by Cooper Curtice who made a special study of the tick, and its development. For the description see Parasites, Ixodes. Among the most marked and distinctive features of the female are the extreme shortness and relative breadth of the rostrum, the slender palpi, the eight rows of spines on the lower surface of the labium, the smooth mandibles with terminal hooks, the limbs long, slender, in seven segments, and each furnished with a terminal pad (pulvillus) and one hook (fore limbs) or two hooks (hind). Curtice has identified the ticks of hæmoglobinuria in various other countries with the boöphilus. The Garrapata of Mexico and the West Indies, the Hæmaphysalis rosea of Cuba (Koch), the Ixodes Annulata of Florida (Say), the Ixodes Dugesii of Italy (Nequin), the Ixodes Algeriensis and the Ixodes Egypti he found to be identical. There may be some doubt as to the Rhipicephalus Annulatus Microplus of Buenos Ayres, but as it agrees with the boöphilus in size, in the thickness of its rostrum, in the eight rows of hooks on the lower surface of the labium, in its host and habits, in the fact that it transfers the piroplasma to cattle, and that it prevails on the same continent in what were formerly colonies of Spain it is in all probability the same tick. Curtice holds that it was originally a North African tick, which was carried by the Spaniards to their American colonies. The Rhipicephalus Annulatus of Roumania is probably the same, together with the ticks that convey the Piroplasma in the other countries of Europe. There remain the Hæmaphysalis of South Africa and the “Scrub-tick” of Australia to be identified with, or differentiated from the Boöphilus. The life history of the Queensland “scrub” tick coincides with that of the boöphilus of America (Pound). As Australia derived her cattle from Britain it is improbable that the tick was imported from Europe.
Lesions. If the course of the disease has been short, followed by an early death, the carcass may be full and rounded, but if the animal has been sick for five or six days there is marked loss of condition and weight—emaciation. As after any other affection occurring during very hot weather, decomposition sets in early, though not quite so speedily as in anthrax, in which the subject dies full of rich blood. Something, too, depends on the condition at death, putrefaction being manifestly slower in protracted and debilitated cases. The color of the skin, the mucosæ and normally white tissues varies in the same way. As it has been largely seen in our northern States (and Australia) in fat cattle, which contracted the disease in railway cars, cattle markets, or dealers’ or butchers’ parks, etc., the deep orange hue of the white tissues is one of the most marked features, and even the muscles have a deep mahogany yellow hue. In poor milch cows and stock cattle in the South, on the other hand, the icteric hue is often conspicuous by its absence. Cattle killed early for experimental purposes may also show less icterus. The color appears to be influenced largely by the abundance of red globules in the blood when the animal was attacked, by the rapid destruction of these globules, and the saturation of the blood and tissues with hæmoglobin in solution. The presence of ticks on the skin, especially along the ventral aspect, inside of the thighs, on the scrotum, udder or perineum, sufficiently explains the number of minute infiltrations into the derma, the oozing of blood or serum, and the matting of the hairs into little tufts.
The pale, watery condition of the blood was recognized as one of the most constant features in 1868, together with the disappearance of the red globules. The clot is remarkably soft and, at the crisis of the disease, the serum is of a reddish hue by reason of the hæmoglobin in solution. When, however, the urine is no longer stained, the hæmoglobin having been eliminated, the serum assumes its normal pale amber hue. For the first counting of the red globules in this disease we are indebted to the Bureau of Animal Industry. The average count in healthy cattle approximated to 6,000,000 per mm. of blood, and in three days this would descend to 4,000,000, 3,000,000, 2,000,000 or even 1,183,000. The rates of decrease was ⅛ to ⅙ of the entire number in one day. In case of recovery the repair of the red globules was slow, from one to two months being required to bring them up to the normal standard. Lignieres claims recoveries after the count had gone as low as 300,000 per mm., and in fatal cases, a few hours before death, it may be but 31,000 per mm.
In high conditioned animals, with high fever often aggravated by travel, the muscles may be dark and firm, but in those out of condition and in the advanced anæmic stages of the disease the muscles are pale, and there may be subcutaneous œdema below the chest and belly. These last features are especially noted by Smith and Kilborne.
The lungs are usually normal. Sometimes limited congestions, punctiform petechiæ, emphysema and small areas of œdema or hepatization are noticed (Smith and Kilborne).
The pericardium contains a little bloody serum and is marked by petechiæ.
The left heart is usually empty, but the right heart full of fluid, or later, of clotted blood, in the latter case without buffy coat. The endocardium, and especially on the musculi papillares, is marked by petechiæ, punctuate or in considerable patches. The cardiac capillaries are full of blood, with numerous piroplasmata.
The peritoneum often contains a little reddish serosity, and a slight gelatinoid exudation is sometimes found around the kidneys or elsewhere in the abdomen. Petechiæ are frequent.
The stomachs usually show petechiated spots on the mucous membranes, and more or less diffuse congestion. Sloughing of the mucosa at such points is not uncommon, and even perforation of the folds of the third and fourth stomachs. The Bureau of Animal Industry and Lignieres both found these stomach lesions very inconsiderable. The smaller pinhead erosions described by Gamgee were identified by the Bureau of Animal Industry as bites of the strongylus convolutus. The small intestines are usually moderately congested.
The cæcum and colon show more congestion, becoming at times of a deep red or almost black hue, and considerable extravasation of blood may take place. This is especially marked in the rectum, which may be of a port wine hue, comparable to that seen in rinderpest or hæmorrhoidal anthrax. The fæces are often dry and massed in balls in cæcum and rectum, while if diarrhœa has set in, the discharges may be colored with blood or blood elements. Yet in the cases reported by the Bureau serious lesions of the intestines were rather the exception, and some subjects showed scarcely any lesion.
The liver is usually enlarged, averaging three to five pounds heavier than in a healthy ox of the same weight. In these enlarged and congested cases it is of a deep yellowish brown color, and often shows yellow spots on the darker ground. Microscopically each acinus has a bright yellow centre from which yellow radiating canals diverge to join the peripheral gall duct. In the superficial or portal portion of the acinus, the hepatic cells are granular from fatty change, yet the nucleus is usually still recognizable. Toward the central zone it may have disappeared. The further this has advanced, the softer, the more easily pitted and the more friable the liver. The congestion of these radical gall ducts with the dense colored bile, displays the structure of the acini in a clear and beautiful way, which no injection can accomplish. When the affected tissue is teased out and placed under the microscope the inspissated contents of the bile canaliculi may be seen as yellow cylindroid casts sometimes bifurcated to represent the union of the two canals. If stained in Ehrlich’s acid hæmatoxylin, the necrotic elements refuse to take the stain so that the contrast between the dead and the living tissues is enhanced. Fatty degeneration is common in the liver of healthy beef cattle so that this is less significant than the congestion of the acini, and the phenomenal distension of the radical gall ducts with inspissated bile.
The gall bladder is usually full (½ pint to 1 quart or more), and its mucous membrane congested and sometimes petechiated. The bile is thick and viscid, like tar, it may be yellowish green, darkening on exposure and contains hæmatoidin crystals and abundance of flocculi showing bright yellow or orange by transmitted light and reddish brown by reflected light.
The spleen is always enlarged, often enormously so. From an average weight of 1.5 lb. to 1.7 lb. for a 1000 lbs. ox, it will rise to 2, 7 or even 10 lbs. One measured 27 inches long by 7½ inches wide and in the centre 3 inches thick (Rauch). Even in apparent health the Gulf coast cattle have spleens averaging about 2½ lbs.
The spleen is gorged with blood which appears purple as seen through the stretched and attenuated capsule, and darker petechial spots are found at intervals. When cut into, the pulp alone appears dark, brownish red, grumous, and showing under the microscope many red blood cells, larger cells granular and undergoing fatty degeneration, yellow flocculi, crystals of hæmatoidin, and granules of black pigment. It is the excess rather than the nature of these agents that is significant. The pulp may be pressed or washed out, bringing the trabeculæ and Malphigian bodies into view.
The kidneys are most seriously affected in acute and rapidly fatal cases. There may be œdema, with blood staining and even extravasation on their lower surface and in the adipose tissue. The gland may be enlarged and the cortical substance congested of a dark brownish red or black. Its capillaries are gorged with red globules in which the piroplasmata are very numerous. The medullary portion is much paler, and with fatty granules in the epithelium, and oil globules in the tubules. The renal pelvis is more or less petechiated and marked by extravasations.
The bladder is marked by petechiæ and usually contains some quarts of urine more or less deeply stained with hæmoglobin. The depth of color is in exact ratio with the extent and rapidity of the destruction of red globules, and of the elimination of their coloring matter. When the destruction is proceeding rapidly the urine may be as dark as port wine; when their disintegration has lessened it may be pale though the temperature is still high (105° F.) In slight and tardy cases there is reason to believe that the redness of the urine may be omitted altogether as is the icteric discoloration of the mucosæ, and hence cases seen in animals indigenous to the protozoan fever districts, have been described as a distinct disease. In these mild cases and advanced stages there is usually a certain amount of albuminuria remaining. In the early stages the urine is strongly alkaline, effervesces with acids, and has a high specific gravity (1030–1040); later when abstinence and suspended digestion and assimilation causes the patient to subsist on its own tissues the reaction may become distinctly acid and the specific gravity reduced (1010–1020). It no longer effervesces. During convalescence while there is a great deficiency of red globules and other blood solids, the urine tends to become pale and watery, of a low specific gravity, and lacking in even its normal pigments.
The womb will at times show petechiæ and in pregnant cows the fœtus will show sero-sanguineous effusions or even extravasations in the chest or abdomen, and hæmoglobinuria (Lignieres).
Incubation. Outbreaks occurring in the North, in herds into which southern infected cattle have been brought, were at first held to indicate an incubation of thirty or forty days (or even sometimes sixty-five), but this is now explained by the time required for the laying and hatching of the eggs of the mature ticks and the evolution of infecting young larval or seed ticks. The actual incubation, as shown by the subcutaneous or intravenous injection of the blood of an infected ox, extends from three to ten days. The hyperthermia is usually shown on the third day, and the more manifest outward symptoms on the sixth. Extreme heat of the weather, a special susceptibility of the animal infected, and especially a large dose of the blood and protozoa will hasten somewhat the onset, but three to six days may be set down as the rule after the ticks have introduced the parasite into their victim. Cattle taken from the northern states and placed on southern pastures, or passing over trails already well stocked with the ticks, are infected at once and sicken in from three to ten days. Cattle in their northern home placed on a previously uninfested field with southern cattle just arrived, do not suffer for thirty, forty, sixty, and in exceptional cases, even ninety days. The paradox is explained by the time wanted for the laying of the eggs and the hatching of the tick larvæ. The female tick does not lay eggs until she is fully mature, and if the ticks on a southern ox are still immature there is a variable period of delay until the eggs are mature enough to be deposited. Then the ovigerous tick drops off her host and spends one week in laying her eggs. In warm weather these eggs take three to four weeks to hatch, so that usually five weeks elapse before the young (seed ticks) can climb upon the ox and infect him. Add three to six days more for the actual incubation and we account for about six weeks of delay in the appearance of the disease in northern cattle. If we consider further that a wet season occurring after the eggs have been laid and before they are hatched tends to divest them of their protective covering and to expose them to destruction, and that, in any case, a cold season will delay the hatching until the recurrence of warm weather, and that the absence of bovine victims will doom the new-born larva to an arrest of development, so that a further indefinite delay may be entailed, we have abundant explanation of the frequently delayed evolution of symptoms. Yet in general terms the apparent prolongation of incubation is due to fortuitous circumstances which delay the infection, and not to any actual extension of the incubation itself.
Symptoms of Acute Type. Cattle infected outside the area of habitual prevalence and stock from noninfected districts, conveyed into the infected ones in hot weather, usually contract the disease in its acute and fatal form. The period of the year is often significant, a number of animals being attacked at once in the hot dry period of late summer or autumn—July to September in North America, February to May in Argentina.
The first symptom is a rise of temperature, and this may last two or even three days before other morbid phenomena are noticed. It may rise to 104° F. in the first day and later to 107°, 108° or 109°. The more acute the case and the hotter the weather the greater the rise. The highest records are obtained late in the day, the lowest in the morning. The temperature often rises for two to four days, and then suddenly drops with the occurrence of collapse and imminent death. While the thermometer is of the highest value in taking the temperature, yet the extraordinary hyperthermia is easily detected by grasping the root of the horn or ear, or by feeling the nose, feet, anus or lips of the vulva.
After 2 or 3 days the respirations become accelerated to 60 to 100 per minute, and the pulse to 90 to 100 or more. There is complete loss of appetite and rumination after the development of these symptoms, the mouth is hot and it may be dry, the muzzle dry, the head pendent, the eyes dull or semiclosed and congested (usually icteric), the bowels confined, to be relaxed again as the fever subsides. A disposition to stand or lie down in water has been frequently noted. Nervous symptoms are usually present. The extreme dulness, languor, and apathy, the drooping head and ears, the unsteadiness of the support the animal staggering or propping himself up by spreading all four limbs, and the tendency to assume and retain a recumbent position, are marked phenomena in our domesticated northern cattle. The paresis may absolutely incapacitate the animal from getting up. In our wilder range cattle it may show itself in active delirium and Lignieres notes the same of the Pampas cattle in Argentina. The animal lying dull and apathetic (triste), on being approached may raise his head, open his eyes and glare threateningly at the intruder. Sometimes when trembling violently, and swaying ready to fall, he will marshal all his remaining energy to plunge at a man on foot or mounted. Some have become blind and unconsciously walked against obstacles, others have been noticed to run in wide circles.
The milk secretion is suppressed, any little that can be drawn in the advanced stages having a thick, creamy appearance. Abortion is common in the pregnant cow.
The condition of the urine has, however, always drawn especial attention and the names red-water and hœmoglobinuria have accordingly been largely applied to the disease. When, in infected areas, the milder types of the disease have failed to show red-water (Jamaica), the identity of the affection with Texas fever has even been denied. Shortly after the rise of temperature, the urine becomes turbid, and this gradually encreases to a more or less deep red. It assumes its darkest hue when the destruction of red globules is most active and during convalescence it disappears. The suppression of urinary secretion may account in some cases for the absence of this symptom even at the crisis of the fever, yet, as a rule, it is present at such time, and, even though it may have escaped notice during life, the red-water is found in the bladder at the necropsy. It may be of all grades, from the merest tinge of redness to a reddish brown, coffee-grounds, or blackish aspect. The coloration is not due to red globules, but to the hæmoglobin which has escaped from the disintegrating globules, and been eliminated by the kidneys. It is always associated with albumen, and, in the advanced stages and during convalescence, when the elimination of hæmoglobin has ceased, that of albumen continues in small amount for weeks.
The thin, watery appearance of the blood when the disease has reached its height, is constant and even more characteristic than the red-water. A single drop drawn from the skin will show to the naked eye the pale, thin, transparent appearance, but examination under the microscope will confirm this. It remains, too, for a length of time, being recognizable for a month in cases of recovery. In connection with the watery blood, the mucosæ and the muzzle (if naturally white) assume a pallid aspect. This is best marked in the absence of icterus, yet even with the yellow discoloration, the absence of ramifying red vessels is very characteristic.
The bowels are at first constipated and the fæces passed in small, hard balls. Later they may assume a reddish brown or chocolate color, and a covering of mucus and fine blood clots. Diarrhœa supervenes in some cases. In passing the fæces, the everted mucosa usually shows a dark red color.
Course and Duration. Acute cases, above all if traveled or otherwise excited, may terminate in death in 24 to 48 hours. More commonly death will take place in 4 to 7 days. Some patients survive longer, but owing to the extraordinary loss of blood globules and the lesions of important solid tissues they are unable to rally, become steadily weaker and perish in from two weeks to three months. Such animals are pale and bloodless, weak on their limbs, careless of food, and encreasingly emaciated. The pulse is weak and irritable and the eyes sunken. The temperature becomes normal or nearly so, soon after the suspension of the hæmoglobinuria. In cases of recovery there remains for a month or more an unnatural pallor, with marked loss of condition and weakness which are only gradually overcome. Convalescent animals are liable to die of indigestion when overfed.
The mortality averages not less than 90 per cent. in susceptible mature cattle from a healthy district in the hot season. Later, from October onward, the tendency is to a milder type of disease and a greater ratio of recoveries.
Symptoms of the Mild Type. This is seen mainly in cattle indigenous to the Texas fever district, in sucking calves, and in mature cattle from healthy districts but attacked during the cool or winter season. It can be produced at will by placing a limited number of ticks (5 to 20) on the skin of susceptible cattle, especially in the cool season. Again, it occurs as a relapse in cattle that have survived an attack earlier in the season.
Though there are all gradations from the violent type, yet we may set down as mild all cases in which the temperature does not rise above 105° F., running frequently about 103° F. There is loss of appetite, dulness, languor, costiveness, scanty urine, albuminous but not hæmoglobinuric, pallor of the mucosæ, and marked loss of condition. Examination of the blood shows the presence of the parasite in the red globules but usually in the coccus or round form only, and the destruction and disappearance of the globules is much less marked so that, though the blood is anæmic and watery, it is not nearly so much so as in the violent and fatal cases. Without the examination of the blood it may be impossible to distinguish these cases from other febrile affections, yet occurring as they do in the infected district in a number of animals at once, in the cooler season, and showing albuminuria, and marked anæmic symptoms, they should lead to suspicion and a search for the boöphilus on the skin, and the oligocythemia and the protozoa in the blood.
Differential Diagnosis from Anthrax. As anthrax is the one disease with which Texas fever is most likely to be confounded, it may be profitable to collect in tabular form their differential features:
| Protozoan Cattle Fever. | Anthrax. |
|---|---|
| A disease of given districts, wooded, swampy, uncultivated, and places where cattle from these districts are taken. | Prevails in rich, swampy impermeable soils: not permanently implanted on open well drained lands. |
| Always shows Boöphilus, minute or mature, on the skin of the patient. | Has no essential connection with the Boöphilus: latter usually absent. |
| Extends in warm season, as the Boöphilus from an infected district is introduced. | Practically never conveyed by the Boöphilus. |
| Can be carried by the Boöphilus apart from cattle. | |
| Infection destroyed by winter frost above 35° of N. latitude. | Infection not destroyed by winter frosts. |
| Attacks bovine animals only. | Attacks mammals, generally, especially herbivora. |
| Lapse of 5 to 6 weeks after introduction, for tick development, precedes outbreak. | Outbreak may occur at once after introduction of infection. |
| Confined mainly to summer season. | Occurs at any season: most prevalent in summer. |
| Sucking calves nearly immune. | Sucking calves susceptible. |
| Mucosæ become increasingly pale; icteric in violent attacks. | Mucosæ dusky brownish red, not pallid, nor icteric. |
| Urine red or blackish in acute cases at height of the disease. Hæmoglobin. Albumen. | Urine exceptionally red: blood globules, in some cases. |
| Blood becomes increasingly thin and watery: Oligocythemia. | Blood becomes thick, tarry, incoagulable; not watery nor oligocythemic. |
| Blood reddens more or less in air: then becomes darker. | Blood reddens little, or not at all on exposure. |
| Spleen greatly enlarged, purplish, often firm: pulp reddens slightly in air. | Spleen greatly enlarged; pulp very dark does not redden in air. |
| Liver enlarged, congested, often yellow, with fatty and necrotic areas: remarkable yellow injection of radical bile ducts. | Liver enlarged, congested, dark red or violet. |
| Bile abundant, thick, tarry. | Bile fluid. |
| Kidneys pale, or congested, black. | Kidneys congested. |
| Lymph glands slightly enlarged, petechiated or (rarely) hæmorrhagic. | Lymph glands enlarged; often hæmorrhagic, black; peripheral œdema. |
| Pallor in violent cases, in plethoric, icterus of tissues, especially of white ones. | Tissues generally reddish, bloodvessels dark, prominent. |
| Muscles in acute cases mahogany colored. | Muscles pale, grayish, unless they are seat of congestion or extravasation. |
| Blood and its red globules show the pyroplasma in different forms. | Blood shows bacillus anthracis, but no pyroplasma. |
Treatment. Up to the present medical treatment has been essentially unsatisfactory. Lignieres gave quinia sulphate in large doses by the mouth, and in doses of 2½ drams subcutem daily, before and during infection without any visible effect on the progress of the disease. Methylene blue to (¾ to 1¼ dr.), salicylate of soda (7½ drs. daily), arsenious acid (1¼ dr. daily), cacodylate of soda (7½ grs. subcutem) were also tried with no good result. The Metropolitan Board of Health, New York, claimed a succession of recoveries under the use of carbolic acid in the drinking water and sprinkled on the ground so that the animals inhaled it. The cases were, however, the survivors after the first and more acute cases had perished, and the results no doubt depended largely on the mildness of the attacks. The same agent in other hands has not been equally successful. A large number of other agents have been used in vain.
Among the most important measures are a laxative food, like flax seed gruel, a careful picking of all ticks from the surface, the washing of the skin with a 5 per cent solution of creolin, and the removal of the animals to a tick-free pasture, lot, or building. This at once arrests the introduction into the blood of fresh and continuous accessions of the pyroplasma and, if begun early enough, will determine a mild and non-fatal case.
Prevention. The prevention of the protozoan cattle fever is based on the life history of the parasite, and may be directed (1st) to the destruction of the Boöphilus Bovis; or (2nd) to encreasing the resisting power of the exposed animal, to the Piroplasma Bigeminum. 1st. Destruction of the Ticks. (a) On the cattle. The picking of ticks from the skin is effective if the object is to make the animal safe for a few days only as the boöphilus habitually clings to the skin of the one ox from the stage of seed tick to that of ovigerous female, ready to drop off and lay its eggs. An animal going direct to slaughter may therefore be sent through an uninfested district, even in the hot season with a fair amount of safety, after the careful gleaning of the ticks. The greatest care, however, must be taken to manipulate thoroughly all parts of the skin and above all, the ventral aspect, the inner sides of the limbs, the scrotum, udder and perineum. The animals must be shipped at once after such gleaning of ticks with no further opportunity of taking on a new supply, the cars and other conveyances must be cleaned and treated with acaricides and the litter burned as soon as they are vacated, and the cattle must be passed over no loading banks, chutes nor yards that may by any possibility be used for other cattle unless these are going into slaughter house.
The picking will safely remove all the larger larvæ, and the mature ticks which are ready to lay their eggs, but it cannot be implicitly trusted to remove also the all but invisible embryos or seed ticks, and if the host is preserved these grow up and mature, while if they are accidentally dropped or brushed from the surface, they climb upon the first available ox and mature on that. By passing from ox to ox they may be kept alive for a time in the pens adjoining the slaughter house, but fortunately they do not travel over a few feet and if no cattle escape from such pens there is small risk of their preservation.
Dipping or smearing to destroy the seed ticks on the skin becomes an essential adjunct to, or substitute for, picking. The Bureau of Animal Industry has experimented largely on dips with most important and valuable results, even if they have proved only in a measure successful and desirable. Aqueous dips they early discarded. Poisonous agents like corrosive sublimate and arsenic are liable to poison through absorption and licking, with the added drawback that neither these nor calcium sulphide are at all effective in destroying the ticks. Proprietary sheep dips were abandoned on similar grounds. Baths of cotton seed oil were introduced by Francis, but proved not quite effective even when phenic acid, benzine, gasoline, or different mineral oils were added. Paraffin oil gave the best results, and later a staple sold as extra dynamo oil, which in combination with sulphur (1:100) proved most destructive to the ticks, was adopted. But in the hot season, when such dipping is required, any one of these baths produced heating, and illness in the cattle, and together with the exertion and excitement served to rouse into dangerous activity the germs already present in the blood. Ophthalmia, too, was a very frequent result. If the cattle could be kept on their native pastures the dipping might be permissible, but this was to lose the object aimed at—the wholesomeness of these cattle on uninfected ranges. When shipped north in the hot weather the losses were so great as to be prohibitory.
If, however, it could be reserved for use on the southern pastures, to prevent the maturing of the ticks and the laying of eggs for a future generation, it might be employed to rid the infested pastures of the boöphilus, and consequently of infection. The question, then, is reduced to the comparative advantage of the destruction of the ticks, on the one hand, and the cost of frequent dipping throughout the warm season, on the other. The following season there ought to be no ticks left.
Cooper Curtice advocates kerosene 1 gallon in combination with an equal amount of lard, 1 lb. sulphur, and 2 lbs. pine tar. Melt the lard, add the sulphur and tar, bring to the boiling point, cool, add the kerosene with stirring. Rub daily with a brush on the whole skin but especially inside the arms and thighs. On tick-infested pastures it must be continued through the season, and if thoroughly done will leave the fields tick-free the following year. Like oil dipping it would manifestly be incompatible with immediate shipment on a long railway journey, but Curtice vouches for its efficacy as a means of eliminating ticks from southern pastures. The main question is the expense. What would be perfectly adapted to small herds of very domesticated cattle in North Carolina would be a herculean and expensive task in the large herds of Texas. Curtice mentions cotton seed oil, fish oil and even a small proportion of linseed oil as good substitutes for the lard.
Destruction of Ticks on Pastures. Fields, farms and larger areas can be freed from the boöphilus by the thorough application to the cattle pastured on them of one of the above-described methods, provided that no strange cattle are admitted on the land. The ticks are sluggish and, unless carried on the bodies of animals, do not crawl many feet from where they drop. If cattle are kept in the next lot, they should not be allowed to come in contact with the treated or protected stock, but a double fence with an interval of five or six feet, will prove a sufficient barrier to the advances of the tick, apart from its bovine host.
Cultivation of a tick-infested soil for one year or more, with complete exclusion of cattle from November or December until March or April of the second year thereafter, will exterminate the ticks. During the intervening summer there may be plenty of young live ticks on this land, but, in the absence of the bovine host, and blood, these cannot reach maturity, lay their eggs and thus leave new generations. In the course of the second winter therefore they are exterminated. In restocking such land, it is all important to see that the cattle placed upon it do not introduce any ticks on their bodies. Equally essential is it, to see that cattle are excluded from the cultivated land in winter as well as in summer. During warm days ovigerous female ticks, dropped from the skins of such cattle, may produce eggs and larvæ to start a new crop in the coming summer. But as has happened to the wood ticks of the North, so in the South, cultivation of the soil and the exclusion of cattle for a length of time, will exterminate the race of ixodes.
Exclusion of cattle for two winters and the intervening summer will eradicate the ticks even in the absence of cultivated crops. To reach full maturity and propagate its kind, the tick must have bovine blood. If therefore the ticks of a whole season (spring, summer and autumn) are denied bovine victims, and thus cut short in their development, no crop is left for the succeeding spring. If then a cattle pasture is divided in two parts by a double fence with an intervening space of 5 or 6 feet, and if the cattle are confined to one of these parts for a whole year and are transferred to the second half in January after dipping or smearing with ixodicide oil they may be kept entirely free from ticks thereafter. That half of the pasture which is abandoned in the second year, will be tick-free and salubrious in the third year.
Another resort, advised by Curtice when a large tick-free pasture is available, is to place the infected cattle in a pen, and soil them for three weeks, no longer. Then transfer them to another clean pen and soil them there for three weeks more. Then examine closely, and if entirely free from ticks they can be put in the large clean pasture. Should they still carry a few ticks they should be placed in a third clean pen for two weeks more, when they will be tick-free and may be turned into the large pasture without the formality of examination. This is substantially based on the period of parasitism of the tick on the skin of the ox, and its development from the newly hatched larva (seed tick), to the ovigerous female. This period is from three to four weeks. The greater number of the ticks are therefore dropped off as mature ticks to lay their eggs in the first pen, while the remainder are similarly left in the second pen. As the stock leaves the two pens in succession long before the deposited eggs have had time to hatch out, they can take on no more ticks and emerge from the second pen clear and safe. The same pens cannot be used repeatedly, as the eggs develop into seed ticks in 15 days in hot weather, and at once attack cattle.
A stockowner who, independently of his fellows, adopts one of the above expedients in an infested district, is however confronted by the risk of the infection of his herd, by the accidental or careless contact of his cattle with outside ones, and especially with the places where they have been. A broken fence and the entrance of tick infested cattle, or the escape of his tick-free cattle into infested lands, will be the death warrant of all that have not been previously exposed to the disease. Another consideration is that this rigid seclusion of the protected herd must be continued indefinitely so long as ticks are maintained anywhere in the district. The protected animals cannot be driven over a highway without exposing them to almost certain death. Even if a group of adjacent stockowners agree to purify their respective farms, they cannot debar their less careful neighbors from using the highways for tick-infected stock, nor from turning such out on adjoining fields. The veriest scrubs, admitted to the highways, woods and unfenced grounds, keep up the general diffusion of the fever germ and its tick bearer and undo the best directed efforts of any combination of owners of high class and valuable stock.
Well directed legislation, excluding cattle for one or two years, from all woods and unenclosed lands, and enforcing some one of the available methods for the clearing of fenced and stocked lands (cultivation, pasturage by cattle on alternate years, frequent dipping or smearing, passing the stock through a succession of pens), could be made to put an end for all time to the obnoxious tick. If even some other than bovine animals should be discovered to harbor the boöphilus and pyroplasma it could be included in the prohibition and the work made complete. The results would far more than compensate for any necessary outlay. Illinois, with 55,414 square miles of area has over 3,000,000 cattle. The coast states from Virginia to Texas, with Arkansas, Indian Territory and Oklahoma, amount to 767,215 square miles, and in the same ratio should sustain 43,340,040 head. A stock of 25,000,000 at $20 per head would amount to a capital of $500,000,000. Immune from the pyroplasma these cattle would draw freely on the best blood of the north and under the milder skies would compete with the northern cattle on more than equal terms. Living in the open air, they would in the main escape tuberculosis and the other stable-propagated diseases of the north, and their dairy and beef products would enter the market free from suspicion, and command a readier sale, if not a higher price. The stock themselves could be moved to northern markets at all seasons without restriction, and escape the serious losses that now come from a sudden transfer, while pyroplasma-infected and susceptible, to the violent excitement of travel, and the frost-bound destination. Their owners could watch the markets and sell in the best, in place of being compelled, as at present, to hurry them in during November and December, and to sell often at a ruinous sacrifice. With the extinction of the boöphilus the present unrestricted pasturage and all other privileges now enjoyed would return, freighted with a value never borne before, and the few Southern cattle and cattle products need fear no competition in the markets of the world, and could no longer be justly subjected to any restriction.
There would remain the constant danger of the introduction of the boöphilus anew from Mexico, the West Indian Islands and the Central and South American States, where in the absence of frosts the boöphilus cannot be extirpated in the same way, and here accordingly all importation must be forbidden. Cattle from Southern Florida and from islands on our Southern Coast may demand a similar exclusion. There is too much at stake to permit any laxity, and no infected area should be allowed to send out its cattle until it has been abundantly well proved that such district or State is absolutely tick-free.
2d. Immunization: Encreasing the Resistance to the Piroplasma Bigeminum. That cattle can be fortified to resist the attacks of the piroplasma is shown in the immunity possessed by the indigenous herds generally, in the regions infested with this parasite and the boöphilus. To begin with, there may be a survival of the fittest, the more susceptible strains of blood having been long ago cut off. But the immune southern cattle if kept for years outside of the infested area and then returned to it, suffer a mortality about as great as that of northern cattle in the same circumstances. Their earlier immunity, therefore, is not merely a racial difference, but must be due in greatest part to an acquired resistance, and further, this resistance is not permanent but must be renewed at short intervals. The immunity may be in part acquired in the womb of the infested dam, in the last months of gestation, but it is chiefly post-natal through the attacks of the ticks.
a. Infection of sucking calf. The indigenous cattle acquire immunity mainly through the attacks of the boöphilus, in the first month or two when they are still on an exclusively milk diet, that renders the piroplasma practically harmless. Following a parallel method, calves, living on milk alone, can be taken into the infected regions and exposed to the attacks of the ticks with safety, and with the result of protection for the future. Escaping the first invasion, they continue to harbor as many ticks summer after summer, as will reinforce yearly their acquired power of resistance, so that they continue measurably safe though spending the life in the area of the infection.
Francis and Connoway applied this to Jersey calves of two to six weeks old applying to each 25 to 50 ticks. It led to slight hyperthermia, some dulness and inappetence, but on recovery they all gained flesh and condition. Two died from exposure but necropsy showed no sign of Texas fever. The following summer all were infested with 200 to 500 ticks apiece but not one sickened in consequence. These were Jersey calves (the least susceptible breed) and the experiments were made in cool weather in autumn. The limitation of the practice to the cool fall or winter months renders the operation much more safe.
b. Infecting Older Animals by a limited number of Ticks. Yearling Jerseys, Holsteins and Shorthorn were subjected to 25 to 50 ticks in July, they showed only slight rise of temperature, and later resisted the free exposure to tick infestation. It must be recognized that these were still young animals, with presumably greater resisting power than the mature, but on the other hand they were of the susceptible northern herds, they were first infested in the hottest season, and the acquired resistance appears to have been perfect throughout the succeeding summer. The added precaution of subjecting them, in late autumn or winter only, to the ticks raised in a warm room or thermostat, would add greatly to the safety of the operation. After recovery from the effects of the first crop of ticks, a second crop of 50 to 100 should be placed on the skin so that the system may be thoroughly habituated to them and the measure of resistance correspondingly strengthened.
This measure may be advantageously applied to valuable cattle that are to be moved into the infecting territory, but it has serious drawbacks. The relative strength of the poison introduced by the ticks to the susceptibility of the animals on which they are placed, can never be perfectly gauged, and a certain small but appreciable number of deaths result from this first infesting. This has been observed in North and South America, Australia, Roumania and Turkey. Again, the plan entails the necessity for clean, non infected premises (lots or buildings) for each fresh lot of cattle, as the places previously used are left in a tick-infested condition, and are likely to furnish a dangerous excess of ticks to any susceptible animal. The buildings could, of course, be disinfected and purified, but this entails considerable expense.
c. Infection by Graduated Injections of Blood Containing the Pyroplasma. Up to the present this is the most promising method of securing resistance to the pyroplasma. It is advised to take the blood from an immunized northern animal or from one indigenous to the infected district. Such an animal is not, however, strictly speaking immunized. It has acquired a tolerance so that it is no longer in much danger of succumbing to the pyroplasma, but it does not exclude the pyroplasma from its system. The micro-parasite is still found in the blood, though mainly in the coccus-like form in the interior of the red globules. The animal to be fortified against the disease is therefore inoculated with the germ of the disease itself, though it may be, at the time, in a somewhat inactive form. If, however, the inoculated animal is specially susceptible, or if the dose is excessive, the disease is produced in deadly form. The virulence is less in the case of blood drawn from a northern animal just recovered from the disease, than from an animal indigenous to the infected district, and which harbors the pyroplasma, it may be in spore form (Lignieres), without showing obvious disease. The former source of the blood is therefore the more desirable, while the latter is the more easily obtained. The precaution, however, should be adopted of reducing the dose when taken from an indigenous animal. Another important precaution is to select the winter or cooler season for the operation rather than the summer.
The animal which is to furnish the blood may be fixed in stocks, or held with a bull ring, or it may be cast so that it can be kept still. The hair is clipped or shaved from over the jugular vein in the upper third of the neck and the surface is washed with soap and water and with a five per cent. aqueous solution of carbolic acid. A thick cord inch (¼ inch) is tied tightly around the back part of the neck so as to compress and raise the jugulars. With a sharp pointed bistuory sterilized by boiling, a small incision is made through the skin, directly over the centre of the jugular and a cannula and trochar ⅒th inch in diameter and sterilized by boiling, is passed obliquely upward through the coats of the vein and the trochar withdrawn. The blood flows through the cannula and is received in a sterilized (scalded) glass beaker. The blood is stirred slowly with a sterilized glass rod until all the fibrine has coagulated when the latter is lifted out and the remaining liquid blood is ready for use. The blood is injected with a hypodermic syringe which, with its nozzle, has been thoroughly sterilized by boiling. The point selected for injection is usually back of the scapula on the middle of the chest. The skin is clipped or shaved, washed with soap, soaked in a five per cent. carbolic acid solution, then pinched up, perforated with the point of the bistuory, and with the nozzle of the syringe passed through this wound the blood is injected into the subcutaneous connective tissue. The slight wound may then be covered with tar or collodion or merely left undressed. The mass of blood in the connective tissue may be diffused through its meshes by rubbing so as to favor absorption.
The dose of defibrinated blood employed is 5cc. if from an immunized northern ox, or 3cc. or even 2½ cc. if from an indigenous animal. The animal operated on should be in good health and condition, well fed, and kept if possible in the shade, in a cool stable, or under trees.
In some respects it is preferable to operate on the animals before they are moved from the north or other noninfected territory, but as there is danger of infection in preserving and carrying the blood, the treatment is more conveniently deferred until the animal reaches the infected region where the blood can be had fresh. In such cases the animals should be shipped in carefully disinfected cars, and before leaving they should be liberally oiled or larded so that the ticks will not climb upon them, in being led to their stable. They must be kept stabled until the febrile effects of the injection have entirely passed, usually a month or more.
d. Injection of Blood from Bodies of the Ticks. In view of the difficulty of shipping infected blood without danger of contamination or sepsis, and the occasional accidents that happen to animals injected with such blood outside of the infected area, attempts have been made with dried blood, or that charged with antiseptics (calcium oxalate), or that had been frozen, but in every instance the virulence of the pyroplasma was destroyed. Dalrymple and Dodson availed of the blood drawn by mature ticks, which, in their blood-gorged condition, were shipped to the points where the injections were to be made. The mature ticks charged with blood were taken from infected indigenous cattle, and at once shipped. On their arrival they were washed externally with a mercuric chloride solution (1:1000) to destroy any adherent saprophytic or other bacteria, mashed in a sterilized mortar, with a few cubic centimeters of boiled water and the fluid portion drawn off and injected subcutem, into the animal to be protected. From 3 to 12 mature female ticks were used for each animal. The results were the same, only milder than when the blood of the indigenous animal was used direct, and the subsequent tolerance of the pyroplasma proved satisfactory.
It is difficult to explain the moderate effect of the considerable mass of blood injected in such cases, as compared with the deadly effect of the small amount that could come from the insertion of the rostra of even 50 or 100 ticks. But perhaps the venomous saliva instilled in concentrated form into the bites, protects the pyroplasma in the very limited area, until it gains sufficiently in numbers and force to hold its own even in the circulating blood.
Limited Value of Artificially Induced Tolerance. It must be added that all these measures for securing a partial immunity in the individual animal, and which enable us to safely introduce previously susceptible cattle into an infected district, virtually imply the continuance of the infection and infection bearer (boöphilus) for all time. They give no promise of the extinction of the bovine infection at even a remote future time, nor the abolition of the taxes for prevention, which must oppress the southern cattle owner so long as the disease continues. They are most valuable measures truly, but mere temporizing ones at the best, and they could just as well give place to the more sanitary, economical and statesmanlike measures for its radical extinction.
Marketing of the Beef. The piroplasma is not communicable to man, so that the carcasses of well conditioned cattle, which bear the infection need not be rejected as human food. It is only in severe and advanced cases in which anæmia, emaciation and pallid innutritious muscles are marked features, that the flesh is objectionable, and then only as being somewhat lacking in nutriment and digestibility,—not because of poisonous qualities. Danger of infection to cattle might be apprehended, but, if used outside the infected area, the second condition of the disease—the boöphilus—is lacking, while within the existing area of prevalence of the fever, the propagation from the carcass to the animal is infinitely less likely than from one live animal to its fellow.
Federal Restrictions on Cattle within Infected Areas. The orders of the Secretary of Agriculture prohibit the removal of cattle from the following states and territory into any states that extend northward of the line indicated: California, Oklahoma, Indian Territory, Arkansas, Tennessee, Virginia and the states south of these to the Gulf of Mexico. Exceptions are made in the case of fat cattle, sent out of an infected area, for immediate slaughter at the point of destination; conveyed in cars or boats placarded as containing Southern cattle and receiving no other; fed and watered enroute in yards that admit no local or other cattle and which can be reached without passing over any highway or unfenced open ground; and unshipped at their destination directly into yards reserved for Southern cattle only and within the same enclosure as the slaughter house. If reshipped the cars used must be subjected to the same restrictions. The cars, boats, chutes, alleyways, pens and troughs are to be disinfected by thorough cleaning; by saturation of all wood work, etc., with a mixture of 1½ ℔s. lime, ¼ ℔. phenic acid and 1 gallon of water, or ¼ ℔. chloride of lime in a gallon of water, or a jet of steam under a pressure of 30 ℔s. to the square inch. The manure and litter must be mixed with quicklime, or saturated with a 5 per cent. solution of carbolic acid, or secluded in a well fenced enclosure from February 1st to November 15th of each year. This is made the duty of the stock yard companies.
Cattle may be freely moved north from the infected area at any time from November 1st to December 31st, if inspected by an officer of the U. S. Dept. of Agriculture and found free from infection.
Provision is also made for sending infected cattle northward at any season, if they have been first dipped and pronounced free from the disease by an inspector of the department.
Cattle from Mexico are admitted under analogous rules.