Part 79

All indications point to Asia or North Africa as the primal home of the disease, as they still prove its perennial one.

Causes. The disease is transmitted by contagion and almost exclusively in the act of coition. Hayne has seen the affection in geldings, and Haxthausen in mares that had never been served. Schneider, Buffard, Nocard, Blaise and others have transmitted it freely by inoculation of blood and nervous matter, so that the possibility of infection through other channels than the generative organs must be admitted. But such irregular means of casual infection are so rare, and the probability of transmission of the virus from a non-breeding animal is so remote that in the practical measures of sanitary police, the breeding horses alone need be taken into account.

The extra vascularity of the male and female generative organs at the period of coition undoubtedly favors infection, as a latent or apparently recovered case will relapse under its frequent repetition. The abrasion of the epithelial surface also forms infection atria and favors new multiple points of infection.

The disease has occurred congenitally (Rodolff, Jessen). It has been claimed that the higher bred horses with lighter frames are the more susceptible (Fischer), but this is probably a delusion, the disease having been often introduced by the Barb and Arabian and propagated among their grade descendants. The heavy Percheron shows a very ready susceptibility and a virulent and fatal form of the affection.

Microbiology. That the affection was due to a microbe was clearly shown by its absence from every part of the world into which infected horses had not been brought. The secluded countries, Belgium, England, Scandinavia, that breed their own horses, the distant Australia, New Zealand and South America remained free in face of the constant presence of the infection in different parts of Central and Southern Europe, in Africa and Asia. The horses of America and South Africa showed a ready susceptibility to the virus brought by infected horses, and rigorous sanitary police control speedily cleared a district of the trouble.

Thanhoffer found in the blood, vaginal mucous, testicle, semen, spinal fluid, myelon, and roots of the dorsal and lumbar nerves cocci, especially streptococci and less constantly bacilli, to which he attributed the malady. More recently Schneider and Buffard have apparently demonstrated that an infusorian, the trypanosoma of dourine, is the essential pathogenic agent.

The Trypanosoma Equiperdum varies greatly in form at different stages of its growth or in different media. In the exudate of the slight early tumefaction, without as yet other symptoms, it is found as minute granules in groups, as larger spherical very refrangent bodies like very large cocci, each having a strongly staining nucleus, and as larger bodies in which a delicate membranous covering encloses one, two or three masses of chromatin and extends to form one or more points (club-shaped or fusiform). Each chromatin mass has a nucleolus on its outer surface or slightly apart from it. Twenty-four hours later there may be added: First, short, thick chromatin bodies, with two slightly undulating, pointed, membranous prolongations. Second, more delicate, fusiform bodies, each with one chromatin nucleus, a detached nucleolus, and the membrane prolonged into two actively moving flagella. Third, larger pyriform bodies with chromatin nuclei and nucleoli and the membrane prolonged into one or several flagella. Fourth, fusiform bodies, thick or delicate, each having a chromatin nucleus and nucleolus, and arranged singly or in groups of two, four, six or more, united together at one end and diverging at the other to form a stellate mass. These last, 20 to 30μ long by 1.5 to 2μ broad, may perhaps be the adult form of the parasite from which the small granular or spore forms found in the most recent lesions are derived. The fusiform outline, the deep staining central mass, with its adjacent nucleolus, and the pointed or flagellate membranous prolongations, more or less motile or undulating, are characteristic features.

In its morphology and evolutionary forms the trypanosoma of dourine has not been shown to differ from that of surra, nor the nagana or Tsétsé disease, the granule form, the spherical, the club-shaped or pyriform, the fusiform with more or less stellate grouping, are characteristic of all (Lydia Rabinowitsch, Kemper, Schneider, Buffard). The distinction is found in the pathogenesis of the two diseases.

With active cutaneous or mucous lesions, the parasite is usually found abundantly in the blood, sperm, milk, vaginal secretions, and the erosions of the vaginal mucosa or penis. During intermissions, however, and in the absence of local lesions, examination of the blood may fail to detect it, yet its inoculation on a dog will usually produce the affection. It disappears from the blood and tissues with great rapidity after death, so that, to prove successful, inoculations should be made before death or immediately after. They are ineffective after 48 hours.

Schneider and Buffard, Nocard and others found the trypanosoma in the blood and exudates of horses, asses and dogs, suffering from dourine, and failed to find it, in the same localities, in animals of the same species which were free from dourine. The infected blood, preserved for 24 hours in sealed glass tubes, and then inoculated on two dogs produced characteristic dourine, with the extensive production of trypanosoma in the blood, the destruction of blood globules, and the pathognomonic local lesions. Inoculation of two other dogs, with the same material, at the end of 48 hours produced a slight transient hyperthermia only, without local lesions or propagation of the parasite in the blood. The same blood inoculated after 15 days produced neither local lesion nor fever.

Lesions. Horse. In the early stages are found a phlegmonous or œdematous swelling of the sheath, scrotum, penis and inguinal glands and a yellowish liquid effusion into the scrotal cavity. The skin covering these parts may show a papular or vesicular eruption or if this has passed, a mottling with white spots shows where the lesions have been. Later still the inguinal glands are shrunken and have undergone fibroid degeneration and induration and the testicles, swollen or shrunken, contain centres of caseation. The connective tissue of the epididymus and cord is the seat of a gelatinoid exudation. The walls of the scrotum may be greatly thickened and the seat of abscess or of caseous degenerated hyperplasia. In advanced cases the testicles are usually abnormally small even if the scrotal mass is enormously distended. The sheath and penis may be the seat of more or less numerous ulcers, and swellings, contractions and distortions of the latter organ are not uncommon. The penis may, however, retain its normal dimensions. The walls of the lymphatics in the inguinal region may be the seat of hyperplasia, the thickening causing them to stand out like cords as in glanders. In the advanced stages the muscles, especially those of the hind limbs, become pale and atrophied.

The nerve centres undergo profound changes which have been studied by Thanhoffer. The pia mater in the affected parts of the spinal cord is the seat of active congestion and thickening. The central canal of the cord is dilated (syringomyelia) more at one point than another, contains more than the normal amount of liquid, and the neuroglia around it is thickened and fibrous (sclerosed). The substance of the cord, both white and gray, shows congestion, blood staining, at points foci of softening, and at others induration (hyperplasia of the neuroglia). The nerve cells are modified in various ways, some being granular, some discolored by fine granular pigment, some having enlarged and multiplied nuclei, and some show vacuoles. The nerve filaments often show a granular degeneration extending from the nerve cell into the axis cylinder, and the latter is liable to be varicose or uneven in size. In the affected portion of the cord leucocytes are numerous and hyperplasia is often present. The neuroglia especially tends to encrease, and apart from the foci of softening tends to give a special firmness to the substance. At intervals, in the perivascular spaces, may often be found minute (microscopic or macroscopic) blood clots. The subarachnoid and subdural fluid is encreased and may be pinkish. At the roots of spinal nerves, especially in the dorsal and lumbar regions, a gelatinoid exudate may invest the nerve, distending the connective tissue beneath the neurilemma and even occupying the interval between the nerve filaments. Sometimes large corpuscular bodies are found between the nerve fibres.

The cerebral meninges, especially the pia mater, are congested and opaque. Foci of softening are by no means uncommon and the cerebral ventricles contain an abnormal quantity of fluid.

The bony tissue generally has lost its consistency and the medullary matter may be unduly reddened. The large joints contain an excess of synovia somewhat pinkish in color, and the ligaments of the hip joints are often congested, thickened and softened. The articular cartilage may even show patches of blood staining.

The intestines are usually nearly empty, soft, pale and flaccid, and Ruthe has in one case observed rounded ulcers on the mucosa. Fibroid thickening on the peritoneal surface may indicate a previous exudate.

The mesentery is thickened, with infiltration and has a yellowish discoloration and the mesenteric glands are usually enlarged, softened and friable, though sometimes firm and contracted. The lymph glands adjoining the generative organs are often swollen, pigmented and studded with foci of caseation, varying in size from a pea upward.

The liver is softened and congested or fatty. The spleen is small.

The kidneys are usually large, but flaccid, pale and bleached.

The thoracic organs may show little change, though hypostatic inflammation and foci of caseation or suppuration may be present.

The blood is pale and watery and forms a loose, pale, diffluent clot, while there is an extraordinary diminution of red globules and a relatively great encrease of leucocytes.

In advanced stages the muscles are pale, anæmic and shrunken especially those of the hind limbs.

Mare. In the mare in addition to the lesions of the internal organs and blood, the following may be noted in connection with the generative system. Phlegmonous or œdematous swellings, sores or ulcers on the lips of the vulva, and on the vulvar and vaginal mucosæ. The parts become variously distorted, and the vulva, habitually open may expose the swollen and ulcerated clitoris. A crop of papules or vesicles, running into sores or ulcers may appear on the urethral orifice, the vulva and adjacent skin, and even though overlooked, their seats are marked later by loss of cutaneous pigment and the formation of small white spots. The mammæ are sometimes inflamed, œdematous and tender, with suppurative or necrotic foci and the adjacent lymph glands are enlarged by infiltration or contracted by sclerosis.

Dog. These resemble those in horses. In the bitch genito-urinary congestion, inflammation and catarrh, subcutaneous infiltration under the belly and inside the thighs, swelling of the inguinal lymph glands, emaciation, and pallor and atrophy of the voluntary muscles are marked features.

Symptoms. Horse. Incubation may last from one to eight weeks (Maresch), but is usually 11 days from the infecting service. It may be abridged by a special susceptibility, and by repeated infections and hence the more acute cases are especially seen in the male in daily service. In some such subjects local genital infiltrations are speedily followed by paralysis or vertigo which cuts off the patient in a few days.

More commonly the malady is chronic though varying in different countries, epizoötics or even in particular cases.

The first symptom is slight swelling of the anterior border and raphe of the sheath, which gradually extends backward to the scrotum and inguinal region and forward on the abdomen it may be as far as the brisket. This may be hot and painful, but is usually œdematous, cool and painless. The infiltration affects the end of the penis, the meatus may be red and angry with a slight muco-purulent discharge, and red spots vesicles and ulcers may stand out clearly on the pigmented surface. Williams never saw such eruptions in the American cases and doubts their existence except as the result of injuries. There are frequent semierections and service is still possible. Later the engorgement extends to the specially pendent testicles, inguinal glands and others adjacent. Paraphymosis is occasionally seen or, more commonly, the penis hangs out of the sheath soft and flaccid and erection seems impossible. The local swelling may become excessive, pressing the testicles up against the inguinal ring, or suppuration and extensive abscess may follow. Appetite is retained and the temperature remains moderate (100° to 102° F.).

The local swellings may almost completely subside, except a slight tumefaction of the end of the penis, hence some (Fischer) have held that the cutaneous lesions are the primary ones, yet the start of infection at the generative organs and the fact that a stallion often infects a number of mares before there is any suspicion of his own infirmity is evidence enough of the genital seat of the earliest lesions.

The cutaneous lesions, which are essentially secondary, but highly characteristic, appear from forty to sixty days after the infection (Schneider and Buffard). They are from a quarter of a dollar and upward in size (in some old horses much smaller), and rise abruptly from the healthy skin, becoming the more marked that the hairs upon them stand erect. These may arise suddenly and subside again in one day, or give out a serous exudate which mats the hairs into a tuft. They may, however, last four or five days. These are more patent after a full drink of water, or after sprinkling or sponging with water. Even when they have been overlooked these results may often be seen later on colored skins, in the presence of many circular white spots entirely devoid of pigment. The most common seat of these cutaneous lesions is the hind parts (anus, tail, croup, quarters), but they may appear on the sides, neck, shoulder or thighs.