Common Diseases of Goats
Goats harbor several species of coccidia but not all exhibit clinical coccidiosis (see Coccidiosis). Adult goats shed coccidia in feces, contaminate the environment, and infect the newborn. As infection pressure builds up in the pens, morbidity in kids born later increases. Signs include diarrhea or pasty feces, loss of condition, general frailness, and failure to grow. In peracute cases, kids may die without clinical signs. Rotating all the kids through one or two pens is dangerous. To help prevent coccidiosis in artificially reared dairy goats, the kids should be put in small, age-matched groups in outside, portable pens that are moved to clean ground periodically. Eradication is not feasible, but infection can be controlled through good management practices. Coccidiostats added to the water or feed are adjuncts to a management control program and not substitutes. Chronic coccidiosis is one of the main causes of poor growth in kids and is responsible for the uneconomical practice of delaying breeding for a year until the goat has reached adequate size (70 lb [32 kg] for dairy breeds). In Angora goats kept extensively, the problem is seen at weaning, when the kids are kept in smaller lots and fed supplement on the ground.
In pastured and free-ranging goats, helminthiasis can assume great clinical significance. GI nematodiasis, liver fluke infestation, and lungworm infections all may be seen. Age-related resistance to parasitism in goats is weak relative to that in other ruminants. Although most common in yearlings during their first season on pasture, clinical parasitism may be seen in adults as well. Poor growth, weight loss, diarrhea, a scruffy hair coat, signs of anemia, and intermandibular edema (bottle jaw) may be seen with GI parasitism or liver fluke disease. Haemonchus contortus infection has emerged as a major constraint in the expanding meat goat industry in the southeastern USA. Persistent coughing in late summer and autumn is the usual presentation of lungworms; secondary bacterial pneumonia with fever is a common sequela. Parasitism is insidious on hobby farms, where the problem may not exist for several years and then suddenly explodes as goat numbers continue to increase and facilities become overstocked. Tapeworm proglottids are often noted in goat feces by owners. Although tapeworms are not generally considered to be of clinical importance, their discovery can be used to review the subject of helminthiasis with owners and develop an overall parasite control program (see Gastrointestinal Parasites of Sheep and Goats).
Clostridium perfringens type D can be fatal, and it is not always associated with the classic “change in quality and quantity of feed.” In problem herds, vaccination every 4–6 mo may be necessary, because goats may not maintain protective immunity as long as sheep or cattle when given the same commercial vaccines. Vaccination prevents the acute death syndrome, but occasionally even vaccinated goats may develop acute enteritis. Affected goats develop severe diarrhea and profound depression; milk yield drops abruptly. Death may result in 24 hr. Treatment involves administration of antitoxin, analgesics, fluid therapy, correction of acidosis, and antibiotics.
Vaccination for contagious ecthyma (sore mouth, see Contagious Ecthyma) is not indicated unless the disease exists on the premises. The main problems with infected kids are difficulty in nursing, spreading lesions to the does’ udders or the assistants’ hands, and attendance at goat shows being disallowed. Live virus vaccine is used by scarifying the skin (eg, inside the thighs or under the tail) and painting on the vaccine. Both natural lesions and those resulting from vaccination may last as long as 4 wk, but after the scabs have dropped off, the goats can go to shows.
Chronic wasting is seen quite frequently; it is not a single disease but a syndrome. Generally, if a goat is well fed, kept in a stress-free environment, and has good teeth and a low parasite load, it should thrive and produce. If it does not, and begins “wasting,” it should be culled immediately. The major causes of chronic wasting include poor nutrition, parasitism, dental problems, paratuberculosis, internal visceral abscesses due to Corynebacterium pseudotuberculosis (ovis) or Trueperella pyogenes, locomotor problems (particularly arthritis due to retrovirus infection [CAE virus]), and chronic hidden infections such as metritis, peritonitis, or pneumonia. Tumors are occasionally diagnosed in older goats. These diseases are rarely treatable, and many are contagious; this is the basis for the strict culling policy, which is vital to the overall productivity of a herd.
Paratuberculosis in goats differs from that in cattle (see Paratuberculosis); gross postmortem lesions are less pronounced, and profuse diarrhea occurs less commonly in goats until right before death. Consequently, many cases may go undiagnosed until necropsy. The ileocecal node is the most rewarding tissue for bacteriologic culture and histopathology. Diagnostic testing for caprine paratuberculosis includes agar gel immunodiffusion, pooled liquid fecal culture, direct fecal PCR, and ELISA. The control program for paratuberculosis in goats is similar to that in cattle.
Caprine arthritis and encephalitis (CAE, see Caprine Arthritis and Encephalitis) virus has emerged as an important infectious agent of intensively raised dairy goats, but all breeds of goats are susceptible to this retrovirus. CAE infection in goats can manifest in numerous ways: subclinical, persistent infection; a progressive paresis of young goats 2–12 mo old; agalactia with a firm, noninflamed udder at parturition in bred females; or an arthritic condition with pain and swollen joints in adults. A chronic, progressive interstitial pneumonia or a wasting syndrome may also be seen in adults. CAE infection has been considered primarily to be spread from dam to offspring through virus-laden colostrum and milk, and control programs have been aimed at separating the newborns from the adult population and feeding heat-treated colostrum and pasteurized milk. Infection may persist in herds in which this is practiced due to horizontal transmission between adults. Regular testing and rigorous culling of all seropositive goats, or strict segregation of seropositive and seronegative goats, must be practiced if disease eradication is the goal.
For mastitis in goats, see Mastitis in Goats.