Special Report on Diseases of the Horse Part 66

_Treatment._--Little benefit can be obtained from medicinal treatment, nor is such treatment desirable in this country, where the disease has existed only in restricted areas, and where sanitary considerations demand its prompt eradication.

INFECTIOUS ABORTION IN MARES.

Infectious abortion (also known as contagious abortion, epizootic abortion, enzootic abortion, slinking of colts) is a disease of mares which from a specific cause results in the premature expulsion of the fetus and its membranes from the uterus. It is characterized by an inflammatory condition of the female reproductive organs.

The contagious nature of the disease had not been recognized until recently, the disease being princ.i.p.ally attributed to various conditions, such as traumatic influences, various infectious diseases, spoiled feed, drugs, and other factors. Ostertag was the first to study premature births in mares, attributing as the cause of the same a streptococcus, which he was supposed to have been able to use successfully in artificially producing abortion, either by inoculations or feeding. His findings could not be substantiated by other investigators.

The earliest appearance of the disease in this country was in 1886, at which time it caused considerable damage to the horse-breeding industry in the Mississippi Valley. Smith and Kilbourne investigated an outbreak in Pennsylvania in 1893, at which time they incriminated another germ belonging to the paratyphus B group as the causative factor of the disease. These findings have been subsequently substantiated by many investigators abroad, as well as in this country, notably so by De Jong, Da.s.sonville, and Riviere, and by Good and Meyer. More recently very valuable information was contributed to our knowledge on this disease by Schofield, of Canada, especially with regard to the biological tests for diagnosis. Good suggested "_Bacillus abortivus equinus_" as the name for the specific organism.

The causative agent of this disease is not identical with the germ causing abortion in cattle. It exerts its action, however, in a similar manner, and appears to have, under certain conditions, a predilection for the genital organs of the mare, where it induces certain morbid changes whereby a premature expulsion of the fetus is the result. The germ is usually present in the fetal membranes and also in the aborted fetus. Mares may harbor the infection without disclosing any apparent ill effects. It appears to exert its influence mainly upon the female genital organs, where it may induce an inflammatory condition of the uterus.

The infected animals may carry the fetus through the normal period of pregnancy, giving birth to either a normal or a weak colt, or again abortion may take place at any time during pregnancy, mostly, however, from the sixth to the ninth month.

_Symptoms._--The symptoms suggestive of abortion are frequently entirely absent. At times the abortion may be ushered in by symptoms of colicky pains, restlessness, and periodical straining; these, however, are by no means constant, especially if the abortion takes place in the early months of pregnancy. The genital organs are usually swollen, showing a mucous discharge. Immediately before abortion the symptoms are more aggravated. Following abortion the discharge is more characteristic, being of a dark-brown color, sometimes even b.l.o.o.d.y, and contains streaky or flaky pus. The fetal membranes in all cases are not expelled with the aborted fetus, but there is a tendency toward retention of these membranes, which frequently has serious consequences upon the health of the animal. At times it becomes necessary to resort to manual removal of the afterbirth, and the inflammation of the uterus and a chronic discharge usually follow such conditions. The expelled fetuses, as a rule, die soon after the abortion, and if the expulsion has taken place at a time close to its full term the fetuses are usually poorly developed and subject to various kinds of digestive and septic disorders. The fetuses do not disclose any particular abnormal appearance on external examination; in many cases, however, the post-mortem examination reveals inflammatory changes of various organs.

The method of infection has not yet been satisfactorily established; nevertheless it is essential that we consider as the princ.i.p.al mode of infection the ways which have been proved for the contagious abortion in cattle. These are especially by ingestion; that is, by taking up the germs with the feed, water, or other means, which have become contaminated with the germs. The infection through the genital organs is probably not so frequent, but in this regard the stallion no doubt plays an important role in the spreading of the disease. Schofield considers this method of infection as the princ.i.p.al source of spreading the disease.

It must be considered that in infected stables the germs may be present throughout the premises, and by keeping animals which have aborted in such stables a contamination of feed and utensils may continually take place, since the aborted mares usually discharge a considerable quant.i.ty of material which is often heavily charged with the germs. The germ is taken up by the body with the feed or water, pa.s.sing from the intestines into the blood, and from there is carried to the genital organs, where it finds suitable conditions for its development. Milk from an infected mare may also contain the germ, and colts may become infected by sucking the milk of infected mothers. In such instances the infection may remain dormant until the colt develops and becomes pregnant, when the organism, finding a condition suitable for its development, produces the disease.

On the other hand, stallions used in covering infected mares may be carriers of the germs, and when used for the breeding of healthy animals may in this manner readily transmit the disease to them.

_Diagnosis._--Contagious abortion may be diagnosed by the changes which occur in the fetal membranes, and also in the expelled feces. In order, however, to substantiate a diagnosis with certainty, demonstration of the germ by microscopical examination is necessary. The occurrence of frequent abortions among the mares in a stable is also an additional evidence of the contagious character of the malady. It must be considered that at times infected mares may carry the fetus to full maturity, in which case the diagnosis is possible only by blood examinations in a laboratory.

Infected animals usually abort only once; however, in a certain proportion of cases they may abort even two, three, or four times in succession.

Animals which establish a tolerance for the infection, and carry the fetus to full maturity, may nevertheless remain a source of danger for spreading the disease.

The tests used in laboratories for the diagnosis are the agglutination and complement-fixation tests, by which the disease may be diagnosed from a sample of blood from a suspected animal. Such tests, however, have to be confined to the laboratories, which are equipped for such work.

_Treatment and prevention._--Medicinal treatment is usually of no avail, and all efforts should be directed toward the prevention of the disease. Various medicinal agents have been recommended and are being exploited for the treatment, but to the present time no satisfactory evidence has been established as to their merits. Bacterial vaccines prepared from the specific organism have been given limited trials, but to date they can not be considered as entirely satisfactory, since it will require considerable experience with them before their usefulness can be definitely established.

The prevention should consist largely in sanitary measures directed toward the disinfection of premises and animals. (For a method for disinfection of premises see article under that heading.)

The following procedure is advised for the disinfection of animals: To prevent a stallion from carrying the infection from a diseased mare to a healthy one the sheath and the p.e.n.i.s should be disinfected with a solution of 1/2 per cent of compound cresol solution, lysol, or trikresol, or a 1 per cent carbolic acid or 1 to 1,000 pota.s.sium permanganate solution in warm water. For this purpose it is advisable to use a soft-rubber tube with a large funnel attached to one end, or an ordinary syringe and tube would serve the purpose. The tube should be inserted into the sheath, and the foreskin held with the hand to prevent the immediate escape of the fluid. In addition to this the hair of the belly and inner side of the thighs should be sponged with an antiseptic.

This disinfection should invariably precede and follow every service.

With regard to the mares, a period of three months should elapse between abortion and a subsequent breeding, and especially if there is any evidence of a discharge the breeding of the animal should not be undertaken. The mare showing signs of abortion should be immediately isolated and the fetus and membranes should be burned. The fetus should never be dragged across a barnyard or stable, but should be removed by other means by which the contamination of the premises may be prevented.

The stall in which the animal aborted should be thoroughly disinfected and the genital organs of the mare washed daily with a disinfectant. The antiseptic washing recommended for the treatment of the stallions prior to and after breeding should be also used for the irrigation of the uterus of mares which have aborted. This treatment should be continued daily until all evidence of discharge has ceased. The isolation of the animal should be carried out for at least one month after the evidence of a discharge has ceased.

By carefully and persistently carrying out the sanitary measures it may be possible to control and finally eradicate the disease.

NAVEL ILL OF COLTS.

Navel ill of colts is also known as joint ill, omphalophlebitis, septic arthritis of sucklings, and pyosepticemia of the newly born. The unfavorable outlook after the appearance of the disease, together with the fact that the disease when present requires the attention of a veterinarian, demands that the breeder concern himself with its prevention.

The disease is caused by a microorganism and several bacteria have been suspected of being responsible. Every one of the suspected organisms is found abundantly in manure and objects contaminated with manure. The infective material gains entrance into the colt through the open umbilical cord as a result of its coming into contact with litter, floors, or discharges from its dam contaminated by one of the organisms which cause the trouble. There are cases on record in which the infection has taken place before birth, and while some investigators a.s.sert that this method is the princ.i.p.al mode of infection still, in a large number of cases, the prophylactic measures adopted to guard against the infection through the navel cord have given good results.

Since infection before birth can not be controlled satisfactorily, we are justified, for all practical purposes, in preventing navel ill by guarding against the infection through the cord at birth or soon afterwards.

Cleanliness of stables where pregnant mares are kept must be insisted upon. This is especially necessary where outbreaks of navel ill have been known to exist. Mares in the last stages of gestation should be placed in a box stall which has previously been cleaned and disinfected.

The bedding should be frequently renewed and the external genitals and neighboring tissues should be kept clean and disinfected with a 2 per cent solution of carbolic acid or 1 per cent liquor cresolis compositus, or any other reliable disinfecting agent. Operations for opening abscesses and removal of afterbirths from cows should not be executed in the immediate vicinity of mares in an advanced stage of pregnancy.

The foal when dropped should be placed on clean bedding. In any event the cord of the foal should be washed in a disinfectant solution and tied at about 1-1/2 inches from the navel with a band or string which has previously been soaked in a disinfectant solution. With a sharp pair of scissors the navel cord is then severed about one-half inch below the band and again disinfected. The ligature should not be tightened, however, until pulsation of the vessels in the cord has ceased. The stump of the cord is then painted with strong carbolic-acid solution, tincture of iodin, or a mixture of equal parts of tincture of iodin and glycerin. The stump should be washed daily with a disinfectant and either painted with iodin mixture or carbolic acid or dusted with some reliable antiseptic healing powder. After five days the parchmentlike dried stump may be cut off and the navel wound washed with a disinfectant solution and dusted with powder until healed.

The cases of navel ill resulting from infection before birth can not well be guarded against. By keeping mares, advanced in pregnancy, in good physical condition, the fetus will be expelled immediately upon the opening of the uterine cavity.

Once the infection of the navel cord has set in, the cord should not be ligated but should be washed in a disinfectant solution and a veterinarian called for the subsequent treatment.

INFECTIOUS ANEMIA OR SWAMP FEVER.

By JOHN R. MOHLER, V. M. D., _a.s.sistant Chief, Bureau of Animal Industry_.

Infectious anemia of horses, known also by a number of other names, as swamp fever, American surra, malarial fever, typhoid fever of horses, the unknown disease, no-name disease, plains paralysis, and pernicious anemia, has recently been the subject of much investigation. The cause of the disease has now been definitely determined as an invisible virus, which is capable of pa.s.sing through the pores of the finest porcelain filters, like the infection of foot-and-mouth disease, rinderpest, hog cholera, and similar diseases. The disease is most prevalent in low-lying and badly drained sections of the country, although it has been found on marshy pastures during wet seasons in alt.i.tudes as high as 7,500 feet. Therefore proper drainage of infected pastures is indicated as a preventive. It is also more prevalent during wet years than in dry seasons. It usually makes its appearance in June and increases in frequency until October, although the chronic cases may be seen in the winter, having been contracted during the warm season.

_Cause._--It has been conclusively proved that infectious anemia is produced by an invisible filterable organism which is transmissible to horses, mules, and a.s.ses by subcutaneous inoculation of blood serum. The virus which is present in the blood may be transmitted to a number of equines in a series of inoculations by injecting either the whole blood, the defibrinated blood, or the blood serum which has been pa.s.sed through a fine Pasteur filter, thus eliminating all the visible forms of organismal life, including bacteria, trypanosoma, piroplasma, etc. This virus has also been found to be active in the carca.s.s of an affected animal 24 hours after death.

Following the injection of the infectious principle there is a period of incubation which may extend from ten days to one and one-half months, at the end of which time the onset of the disease is manifested by a rise of temperature. If uncomplicated, the infection runs a chronic course, terminating in death in from two months to one and one-half years, or even longer. The probability of the virus being spread by an intermediate host, such as flies, mosquitoes, internal parasites, etc., is now receiving careful investigation.

From experiments already conducted it appears that this disease, formerly supposed to be confined to Manitoba and Minnesota, is more or less prevalent in Kansas, Nebraska, Colorado, Wyoming, Montana, North Dakota, Virginia, Texas, and New York. It also occurs in Europe, having been reported in Germany under the name of infectious anemia and in France as infectious typho-anemia.

_Symptoms._--The disease is characterized by a progressive pernicious anemia, remittent fever, polyuria, and gradual emaciation in spite of a voracious appet.i.te. It begins to manifest itself by a dull, listless appearance and by general weakness, the animal tiring very easily. This stage is followed closely by a staggering, swaying, uncertain gait, the hind legs being mostly affected. There is also noted a weakness and tenderness in the region of the loins, and at the same time the pulse, though weak, stringy, and intermittent, increases in rapidity and may run as high as 70. The temperature may rise to 103 F. or higher, remaining high for several days, and then dropping to rise again irregularly. Toward the end of the disease the temperature occasionally remains persistently high. The horse may improve for a time, but usually this improvement is followed by a more severe attack than the first.

Venous regurgitation is sometimes noticed in the jugular before death.

The quant.i.ty of urine pa.s.sed is enormous in some cases. Death finally occurs from exhaustion or syncope.

The blood shows a slight decrease in the number of white blood cells, while there is a gradual but marked diminution of red corpuscles, the count running as low as 2,000,000 per cubic millimeter, the normal count being 7,000,000. If the blood is drawn from such an animal, the resulting red clot will be about one-fifth of the amount drawn.

Occasionally a slow dripping of blood-tinged serum from the nostrils is observed as a result of this very thin blood oozing from the mucous membranes. Petechiae, or small hemorrhagic points, are sometimes noticed on the nict.i.tating membrane and conjunctiva, while paleness of the visible mucous membranes of the nose and mouth is usually in evidence, although they may have a yellow or mahogany tinge. Often a fluctuating, pendulous swelling may appear on the lower lip, point of elbow, sheath, legs, under the belly, or on some other pendent portion, especially late in the disease, which is indicative of poor circulation, thinning of the blood, and consequent loss of capillary action.

_Lesions._--After death the carca.s.s is found to be very much emaciated and anemic, the visible mucosa being very pale. This marked absence of adipose tissue makes the skinning of the animal a difficult task.

Subcutaneous and intermuscular edema and hemorrhages are frequently observed, although in many cases it is remarkable to see how few macroscopic lesions may be present. The predominating and most constant lesion is probably the petechiae, so often observed in the muscle or on the serous membranes of the heart. The heart is generally enlarged and may be the only organ to show evidence of disease. In other cases the lungs may be studded with petechiae, with a serous exudate present in the thoracic cavity. In addition to the petechiae already noted, the pericardial sac generally contains an increased quant.i.ty of fluid. The abdominal cavity may show peritonitis and a hemorrhagic condition of the intestines, which probably result from overfeeding in consequence of the ravenous appet.i.te. The liver, although usually normal, sometimes presents a few areas of degeneration. The spleen is at times found to be enlarged and covered with petechiae. The kidneys may appear normal or anemic and flaccid, but microscopically they usually show a chronic parenchymatous degeneration. The lymph glands may be enlarged and hemorrhagic.

_Diagnosis._--The diagnosis of the disease is not difficult, especially in advanced stages. The insidious onset, remittent fever, progressive emaciation and anemia, unimpaired or ravenous appet.i.te, staggering gait and polyuria are a train of symptoms which make the disease sufficiently characteristic to differentiate it from other diseases affecting horses in this country. The peculiar relapsing type of fever, the great reduction in the number of red blood cells, and the absence of eosinophila are sufficient to differentiate it from the anemias produced by internal parasites, while it may be readily distinguished from surra by the nonsusceptibility of cattle and by the great ease with which the trypanosoma may be found in the latter affection.

_Prognosis._--The prognosis of the disease is very unfavorable.

Veterinarians in different sections of the country where it is prevalent report a mortality of 75 per cent or even higher. Recovery takes place only when treatment is begun early or when the animal has a long convalescent period.

_Treatment._--The treatment of the disease has so far been far from satisfactory. The iodid, permanganate, and carbonate of potash have been used. a.r.s.enic, axytol, quinin, and silver preparations have been suggested, but all have been uniformly without success. Intestinal antiseptics have been resorted to, and the results are encouraging but not altogether satisfactory. Symptomatic treatment seems to be the most dependable. For instance, Davison, of this bureau, was able to reduce greatly the mortality from this affection by giving an antipyretic of 40 grains of quinin, 2 drams of acetanilid, and 30 grains of powdered nux vomica four times daily. In the late stages, with weak heart action, alcohol should be subst.i.tuted for acetanilid. Cold-water sponge baths may be given, and in addition frequent copious injections of cold water per r.e.c.t.u.m, which has a beneficial effect in reducing the temperature and in stimulating peristalsis of the bowels, which, as a result of the disease, show a tendency to become torpid during the fever. Purgatives, on account of their debilitating effect, should not be given unless absolutely necessary, but laxatives and easily digested feeds should be given instead. Not infrequently a dirty yellowish tinge of the visible mucous membranes has been observed, in which cases 20 grains of calomel in from 2 to 4 drams of aloes in a ball, or 2-dram doses of fluid extract of podophyllin, may be given. Following the subsidence of the fever, a tonic should be administered, composed of the following drugs in combination:

a.r.s.enious acid grams 2 Powdered nux vomica do 28 Powdered cinchona bark do 85 Powdered gentian root do 110

These should be well mixed and one-half teaspoonful given to the affected animal at each feed.

As in the case of all other infectious diseases, the healthy should be separated from the sick horses and thorough disinfection of the infected stables, stalls, litter, and stable utensils should be carried out in order to prevent the recurrence of the disease. As a disinfectant the compound solution of cresol, carbolic acid, or chlorid of lime may be used, by mixing 6 ounces of any one of these chemicals with 1 gallon of water. One of the approved coal-tar sheep dips may also be used to advantage in a 5 per cent solution (6 ounces of dip to 1 gallon of water). The disinfectant solution should be applied liberally to all parts of the stable, and sufficient lime may be added to the solution to make the disinfected area conspicious.

Investigations are now in progress with a view of producing a vaccine or serum that will protect horses that have been exposed to the disease.