PROTOZOAN ICTERO HÆMATURIA IN SHEEP. PALUDISM OF SHEEP. CARCEAG.
This is described by Babes and Starcovici as prevailing among sheep in the delta of the Danube, and held by them to be identical with the Roumanian Hæmoglobinuria of cattle (compt. rend. de l’Acad. des Sciences, 1892). Its essential cause is a piroplasma affecting the red blood globules, and very analogous to that of the protozoön of Texas fever, but its especial election for the sheep shows a specific difference, inasmuch as the Texas cattle fever does not attack sheep. Not only the parasite, but the symptoms and lesions as well, furnish a close counterpart to those of the cattle infection. It remains to be seen whether the pathogenic difference is due to a distinction in the piroplasma or to the absence from the Southern States of America of the particular tick or other insect which attacks the Danubian sheep.
Bonome (1895, Virchow’s Archives) describes the same disease as prevailing in Italy, describing the parasite and lesions at great length.
Finally my colleague Dr. W. L. Williams, and later Dr. Knowles, have identified the disease in the upper part of Deer Lodge Valley and the lower part of Silver Bow Valley in Montana, prevailing among sheep only, extending year by year, and proving disastrous to the sheep husbandry. Sheep were introduced into these valleys as early as 1875, but it was only in 1891 that the flock masters recognized the existence of this disease. By 1895 it prevailed over an area of 300 square miles. It made its advent in 1891 in four or five large flocks (2,000 to 10,000 head each) on land which they had occupied for nine years, and so disastrously that several sheep ranchers, after an experience of a year or two, sold out to the butcher and abandoned the sheep industry.
All or nearly all cases seen in 1896 were in parturient ewes, (4 to 6 days after parturition), the constitutional condition attending on lambing proving a most potent factor in causation.
The protozoön repeated the characters of that found in the sick sheep in Italy and the Danubian delta, and the conditions of the blood and the structural lesions supported the idea of identity.
Altitude seems to have little or no effect as a causative factor, as the disease is domiciled alike on the low alluvium of the Danube and the Deer Lodge Valley of Montana over 5,000 feet above the ocean. In both regions there is the common condition of inundation or its equivalent irrigation, for the Montana range is dry and arid, interspersed with alkaline bogs inimical to vegetation, but prolific and fruitful under irrigation. The Montana disease has been attributed to mineral poisons carried on the winds from the extensive copper smelters in Butte and Anaconda, but the smelters had been in existence for eight or ten years before this disease was observed, and from its appearance the infection has gradually extended, attacking sheep only, and sparing other domestic animals, which would have suffered as well from a mere mineral poison on the vegetation. The doctrine of a mineral poison is equally contradicted by the habitual prevalence of the disease in spring and autumn, while it is dormant in winter and summer. In winter the flocks eat hay cut from the richer valley lands and meadows, while in summer they are pastured on the foothills and mountains, and drink from the mountain springs surrounded by alkaline bogs. The autumn outbreak occurs long after the mountain grasses have dried up, when the flocks are thrown back on the supplies obtained from the alkaline bogs and the valley pastures. In late winter and early spring the growth naturally starts first in the same boggy and valley areas, and both facts suggest a microbian infection—protozoan or bacteridian. If an intermediate host or bearer—insect or other invertebrate—is to be assumed it implies two generations of these, a spring and an autumn one, in the same season, or otherwise a restriction of such invertebrate to the low valley pastures and the alkaline bogs on the higher levels, and that they disappear from the drier, arid areas in summer. It cannot be an obligate parasite like a louse or melophagus which would be constantly present, nor a musquito absent in early spring. But up to the present no invertebrate host or intermediate bearer has been identified. Cases were at first reported in the Angora goat, but this animal is now known to be immune.
Microbiology. The parasite is formed in the red globules and blood serum of the affected sheep and closely resembles the microbe of Texas fever. In the blood globules the parasite is seen in different forms, round, oval, oblong or curved and from one tenth to one sixth the diameter of the red globule. A single red globule may show from one to four of the microörganisms. They may at times show indications of division, and at others, automatic amœboid movements, from one portion of the blood globule to another, or from the periphery toward the centre. The affected blood globules are usually enlarged, having lost their biconcave outline, and become biconvex or spherical, with irregular crenated surface, and a dull, lustreless appearance instead of a clear red or yellow aspect. The protozoön stains readily in anilin red or methylene blue.
Lesions. The condition of the carcass was good or even high, in sheep attacked when in good flesh, and in which the affection ran a rapid and fatal course. In sheep attacked while in low condition on the other hand, the case tended to be milder and more prolonged, and the body was emaciated and anæmic. Dropsical swellings were common on the ears and sides of the head and neck.
The skin, connective tissue, fat, and other normally white tissues were usually of a yellow color, varying from sulphur to lemon color. The muscles were pale and soft with a yellowish tinge.