CŒNUROSIS (GID, STURDY, TURN-SICK).
Cœnurosis is a disease due to invasion of the animal body by embryos of larvæ of the Tænia cœnurus of dogs and wolves. These embryos only develop freely in the brain substance (Cœnurus cerebralis) and medulla oblongata. The hosts of the larvæ include the calf, sheep, goat, roedeer, reindeer and horse.
The disease was formerly erroneously called “turn-sick,” for the turning is only a manifestation, and even a tardy manifestation, of the disease, while in addition it is not invariably present.
Cœnurosis principally attacks lambs of from three to six months, although it occurs up to eighteen months, and sometimes even two years. It is exceptional, however, in adults. Similarly in the bovine species it usually affects young animals up to the fourth or fifth year.
Cœnurosis with diffuse parasitic encephalitis often remains unrecognised, the animals being regarded as affected with epizootic meningitis of unknown cause or septic intoxication, and when they die the owners are ignorant as to the cause of death. The stage corresponding to turn-sick, which is an advanced phase of the disease, is only seen in animals which have been infested to a slight extent, and in which three or four parasites only, sometimes only one, have attained the brain and developed there. Such cases exhibit all the classic symptoms of turn-sick, viz., turning movements, heaviness, vertigo, etc.
Causation. Cœnurosis is due solely to one cause, viz., the ingestion of eggs or embryos in feeding or drinking.
The Tænia cœnurus lives in the dog, and fertilised segments are passed with the fæces in yards, pastures and fields, and on the margins of roads, ditches and ponds. Amongst damp grass or in water the eggs, which contain more or less well-developed embryos, may retain their vitality for several weeks, and when swallowed the embryos are set at liberty in the intestine.
The six-hooked embryos perforate the walls of the intestine, pass into the blood stream or chyle ducts, and from these points are carried in all directions. Those which gain the nervous centres, the brain or spinal cord, continue to develop; the others, dispersed through different tissues, degenerate and disappear.
Experimental infection with these parasites shows that the brain is invaded after about a week’s time. From the twentieth day the presence of embryos can easily be detected in the superficial layers of the convolutions. They make their way through the grey substance, leaving behind them greenish-yellow sinuous tracts with caseous contents.
The cyst or finn undergoing development can be found at the end of one of these tracts in the form of a little transparent bladder, of a size varying between that of a pin’s head and that of a lentil or a small hazel-nut.
Later the tracts, with their caseous contents, disappear, and the development of many of the vesicles proves abortive. At the end of a month the vesicles, continuing to develop regularly, attain to about the size of a pea. Between the fiftieth and sixtieth days heads or scolices appear in the interior of the vesicle, which then reaches the dimensions of a hazel-nut. From this time the vesicles continue to increase in size until the death of the patient. Usually they become as large as a walnut, or even larger, and the interior contains hundreds of scolices, each showing a head.
Fig. 214.—Brain of sheep. Cœnurosis of the left hemisphere. Œstrus larvæ exposed by trepanation.
The cystic phase only develops completely in animals whose brains contain a limited number of cysts, and in such the signs of turn-sick are well developed. In others, where the numbers are large (ten to fifteen embryos or more), death occurs during the primary stage, usually towards the end of the first month, in consequence of acute encephalitis and without any of the symptoms of turn-sick.
Fig. 215.—Skull of a sheep showing the brain infested with a gid bladder-worm (Cœnurus cerebralis). Two-thirds natural size.
The number of animals attacked is sometimes enormous. Moussu has recorded cases where fifty, one hundred, and even four hundred lambs of one flock were affected. The enormous mortality in such cases is very apt to cause errors in diagnosis. Cœnurosis occurs most frequently during rainy seasons, moisture favouring the preservation of the eggs. Young animals become infected, particularly during the spring and autumn, more rarely in the summer, as prolonged desiccation, say for a period of twelve to fifteen days, destroys the vitality of the eggs, but animals may become infested at any time through drinking contaminated water. Moussu has seen cœnurosis (acute encephalitis) from the last-named cause in the middle of January.
Symptoms. First phase.—Disseminated encephalitis.—The symptoms vary with the phases of evolution of the parasite and of the disease which it causes. After the six-hooked embryos have penetrated to the brain, the animals affected lose appetite and show a certain degree of dulness, which is all the more marked inasmuch as the animals usually affected are young, and therefore should appear bright and alert. Then follow wasting and depression; the animals remain stationary for whole hours together, the head being carried low or inclined to one side. At this stage disturbance in vision and irregularities in movement may appear.
Fig. 216.—An adult gid tapeworm (Tænia cœnurus). Natural size. (After Railliet.)
Fig. 217.—Sexually mature segment of the gid tapeworm (Tænia cœnurus). cp, Cirrus pouch; gp, genital pore; n, nerve; ov, ovary; sg, shell gland; t, testicles; tc, transverse canal; ut, uterus; v, vagina; vc, ventral canal; vd, vas deferens; vg, vitellogene gland. × 20. (After Deffke.)
The eyesight is almost always affected, but the symptoms may vary widely. In some cases the patients seem to be absolutely blind, and strike against any obstacle in their way; in others the power of vision seems to be lost only on one side. All that can be discerned objectively is an inequality in the pupils, together with retraction or dilatation, convergent or divergent strabismus, nystagmus, etc. The humours of the eye appear infected, but examination with the ophthalmoscope reveals lesions of more or less extensive neuro-retinitis.
The visual disturbance is of central origin. The powers of movement may be affected in numerous ways, which at times are extremely difficult to estimate with accuracy. Sometimes the gait is uncertain, inco-ordinated, and hesitant; at others the animal shows lameness or loss of control over a front or hind limb, or over two limbs simultaneously (either the two front or hind limbs or the diagonal limbs), or it may be absolutely unable to stand.
It walks obliquely, or the front or hind limbs collapse; or again, it may persistently lie down, a fact which makes the shepherd think it is suffering from paralysis. On examination, however, no true indications of paralysis can be found; sensation and motor power are both preserved in a modified form.
Fig. 218.—Brain of a lamb infested with young gid bladderworms (Cœnurus cerebralis). Natural size. (After Leuckart.)
Death is very frequent at this stage of the disease; the animals eat little or nothing, refuse drink, and die of exhaustion.
All this general disturbance is of central origin, and is due to disseminated parasitic encephalitis, but up to this point the seat of the disease is not yet clearly apparent.
Second phase.—Turn-sick.—The central symptoms are slow of development, and are due to the progressive growth of one or two, more rarely three or four, fertile vesicles. These are the true symptoms of turn-sick, and it is only after this phase of the disease has developed that the term becomes appropriate.
Left at liberty, the patient usually walks in a circle towards the right or left in an impulsive and irresponsible fashion. Sometimes it describes a circle, always of the same size. In other cases, on the contrary, it travels along a spiral track, getting further from or nearer to the centre as the case may be. The turning movement may become so accentuated that the animal appears to revolve as on a pivot, and if it is confined in a field or straw-yard its legs become caught in the litter and it falls to the ground.
Attempts have been made under these circumstances to discover the exact point of compression, i.e., the point at which the cyst exists, by noting the direction of the turning movement. The diagnosis, however arrived at in this way is frequently illusory, because it is not uncommon to find two or three vesicles, and in any case the most important information in regard to diagnosis is to be derived from the ocular symptoms.
When only one vesicle exists, the turning movement usually occurs towards the side on which it is situated, and the eye of the opposite side is affected with amaurosis.
Fig. 219.—Sheep’s skull, the hind portion thin and perforated, due to the presence of gid bladderworms (Cœnurus cerebralis). (After Dewitz.)
If the cyst is situated near the olfactory lobes, the animal marches with a high-stepping movement and the head drawn back towards the body. If the cyst is in the cerebellum the animal is incapable of moving, because it can no longer co-ordinate its movements. Finally, if the cyst develops in the occipital region, animals turn towards the wind, with the neck raised and the head extended.
At the moment when they fall to the ground they sometimes have epileptiform convulsions, grind their teeth, and salivate profusely. In a severe attack even death may supervene at this point.
Cœnurosis of the Medulla. The embryos may develop in the medulla oblongata as well as on the brain itself. Compression and atrophy of the medulla then give rise to true paralysis.
The animals exhibit paralysis of the hind quarters, unilateral paralysis only, or still less marked signs. Everything depends on the degree of development of the cysts.
Bovine Animals. Cœnurosis in oxen is less important than in sheep. Moreover, it very rarely affects a large number of young animals belonging to one farm. Loss of appetite, dulness and depression are the earliest indications, as in sheep. The gaze seems fixed, the neck is held stiffly and almost rigidly, the animal shows a tendency to vertigo, pushes its head against a wall, or leans the head or neck on the manger or trough.
Fig. 220.—An isolated gid bladder-worm (Cœnurus cerebralis), showing the heads. (After Railliet.)
Inequality in the size of the pupils, amaurosis, hesitating and inco-ordinated movements may also be seen developed in different degrees. The animals have the appearance of horses suffering from “immobilité”—that is, the very peculiar general condition produced by dropsy of the brain ventricles, or from encephalitis. They forget to eat or do not attempt to chew unless handfuls of food are thrust between the molars; they plunge the muzzle into a bucketful of water and do not drink, etc. They take little notice of what passes around them, although they may become greatly excited if an attempt is made to move them, to give them medicine from a bottle, or to set them at liberty, etc. Such attacks of excitement often end in vertigo and in the animals falling to the ground and showing epileptiform movements. All these symptoms may occur with extraordinary variations, due in reality to the peculiar position which the cœnurus occupies.
Second phase. If set at liberty during the first phase of the disease, the animal’s gait appears only slightly disordered, but when a single vesicle has become well developed in one of the hemispheres (and this is usually the case with oxen), the symptoms of turn-sick appear as in sheep, and are equally varied. The patients seem impelled to move in a given direction, whatever obstacles may be in their way. It is not at all uncommon to see them thrusting their heads against walls or trees, falling into ponds or ditches, or attempting to force their way through blind alleys between hay or straw stacks.
After the cyst develops in the cerebellum, the animals are soon unable to move. They may be able to stand in one position, but on any attempt to move they fall.
Lesions. The lesions develop successively from the moment the embryos arrive in the mass of the brain. At first the six-hooked embryos only excite a slight disseminated encephalitis. Their course through the brain is marked by short, greyish-green caseous tracts, the thickness of a needle, which are readily discoverable in the superficial layers. Later these caseous deposits become absorbed, the lesions of disseminated encephalitis diminish and disappear, while a certain number of vesicles after partial development undergo atrophy and disappear. Before long nothing remains but local atrophic encephalitis caused by the development of the vesicles, and from this time the central symptoms begin to appear.
Diagnosis. When the turning movement has developed the diagnosis is generally easy, but it is more difficult during the first period, when encephalitis alone exists; or at least, it is very difficult at this period to discover whether the symptoms are attributable to encephalitis, meningoencephalitis, cœnurosis, tuberculosis, or to some injury.
Fig. 221.—Diagrammatic section of a gid bladder-worm (Cœnurus cerebralis). a, Normal disposition of scolex; b, c, d, e, diagrammatic drawing to show the homology between cysticercus and cœnurus. (After Railliet.)
Prognosis. The prognosis is grave, and very few animals recover. Zürn estimated the cases of recovery in flocks at 2 per cent. In these cases the cysts degenerate and disappear.
Treatment. At the present moment there is no really practical curative treatment.
The best plan appears to be to trephine the skull and remove the cyst, provided its exact position can previously be determined. That, however, is the great difficulty. Its solution presupposes a perfect knowledge of the central nervous system and of the real purport of any apparent symptoms.
On the other hand, in sheep at least, the position of the cyst must always remain somewhat uncertain, because there are generally several, and the symptoms are of a mixed character.
The only treatment, therefore, which would be likely to succeed is difficult to carry out, and more difficult in the ox than in the sheep because of the great development of the frontal sinuses.
It has been mentioned that under exceptional circumstances the cœnurus, if very superficially placed, may cause atrophy of the cranial wall in the sheep by the outward pressure it exerts, and that the points of least resistance may be detected by the touch. In such cases intervention is necessary and is greatly facilitated; but they must be extremely rare, and Moussu declares he has never seen one.
Hartenstein has suggested continuous cooling of the cranium by irrigation or by applications of ice, the local lowering of temperature serving to impede the development of the cœnurus. This method should be tried in animals of high value, and, if the symptoms have not yet become too alarming, recovery is possible. On the other hand, when the symptoms indicate the presence of an old-standing cyst, there is little chance of success. Moreover, the treatment could not be applied where a large number of animals are affected.
It is much better to send the animals to the butcher if they are in good condition. In Scotland, however—particularly in Caithness—operation is said to be frequently practised with success.
Prophylaxis. In well-managed establishments it is easy to avoid the appearance of cœnurosis.
The development of this condition being due to the Tænia cœnurus of the dog, which passes ripe segments containing eggs with its fæces in the pastures, the first indication is to prevent the development of this tænia in sheep dogs, sporting dogs and house dogs, and the sole precaution required is to avoid giving them as food sheeps’ heads containing the bladder-worms. But, as despite these precautions they may accidentally contract infection with Tænia cœnurus by eating the offal of slaughtered animals, it is a wise precaution to administer to all farm dogs, twice a year at least, a dose of some tænicide.
They should be starved and kept in for twenty-four hours, and should then receive a full dose of some energetic vermifuge, such as areca nut, kamala, kousso, powdered pomegranate root, extract of male fern, etc., followed by a purgative. The material passed and the fæces should be burned or mixed with quick-lime. By these simple precautions the losses which formerly proved so heavy may entirely be prevented.