Additional Common Diseases of Goats

Internal parasites (helminths) cause clinically important disease (helminthiasis) in pastured and free-ranging goats in most regions of the world. Nematodes, flukes, and lungworms can all adversely affect goats and cause devastating production losses. Tapeworms generally do not cause notable disease, but because they are visible to the naked eye, they can be a starting point to discuss parasitic infections with producers and develop a parasite control program for the herd. Hobby herds that are allowed access to pasture can have as many parasite-related disease complications as large production herds have. General clinical signs of helminthiasis include weight loss, poor growth, anemia, poor hair coat, submandibular edema (bottle jaw), and diarrhea. Certain parasites (eg, lungworms) may cause specific clinical signs, such as coughing or bacterial pneumonia.

Environmental conditions and stocking density influence the number and severity of parasite-related problems in a herd. Overcrowded herds in warm, moist conditions often struggle with severe helminthiasis, whereas herds grazing in arid or semiarid environments may suffer few production losses due to helminths.

Overuse of anthelmintic drugs has led to increased parasite resistance and increased loss of drug efficacy. A 2008 study determined that, on 48% of small ruminant holdings in the southeastern US, Haemonchus contortus infections were resistant to all anthelmintic drugs available on the market.1 In light of the loss of these drugs for treatment, the current paradigm for helminth treatment in goat herds is to 1) treat only when goats show clinical signs of disease, 2) use fecal egg courts to determine drug efficacy, and 3) use pasture and nutrition management to decrease the risk of exposure. 

Finally, it may be possible to selectively breed individuals with an apparent inherent resistance to parasites. Identification and removal of the highest-shedding goats should also be encouraged, as a few goats are often responsible for shedding a majority of the parasite eggs. 

The FAMACHA system is a low-cost, validated means of assessing the severity of anemia most often caused by H contortus. This system uses a conjunctival-color score to identify animals most likely to have a heavy parasite burden, allowing the producer to then treat or cull, accordingly.

Lice and mites are common external parasites of goats. These organisms seldom cause severe disease, but an extreme infestation can cause anemia and loss of condition. Clinical signs of infestation are pruritus, alopecia, and visible presence of the organisms on the skin and in the hair.

Caprine arthritis encephalitis is a lentiviral disease related to ovine progressive pneumonia, or maedi-visna. Clinical signs include progressive paresis in kids < 1 year old; arthritis (especially swollen carpal joints) in adults; agalactia with a firm udder; and chronic, progressive weight loss. Goats are infected for life and can transmit this disease both vertically and horizontally, through colostrum, milk, blood, and mucus secretions. Serum tests can be used to determine the incidence of caprine arthritis encephalitis in a herd. Culling positive animals is recommended.

Paratuberculosis (Johne's disease) is a bacterial infection of the intestinal wall due to Mycobacterium avium paratuberculosis.Goats can be infected with both the S and C strains of the microorganism. M avium paratuberculosis is shed in the feces, and goats are often infected via a fecal-oral route, generally at a very young age. The pathogen can also be transmitted in utero or through colostrum and milk. Clinical signs, including weight loss, submandibular edema, and weakness, may not manifest until the animals are much older. Diarrhea is not as common in goats as it is in cattle. Johne's disease cannot be cured, and decontamination of the environment is difficult because the bacterium can live for years in the soil. Fecal PCR testing is recommended to identify and remove infected animals. Necropsies on animals that show chronic weight loss are also recommended, to look for internal clinical signs of this disease, such as enlarged mesenteric lymph nodes and thickened intestine with prominent lymph vessels. On microscopic examination, acid-fast-staining bacteria are observed in infected tissue.

Caseous lymphadenitis (cheesy gland) is an infection of the lymph nodes due to Corynebacterium pseudotuberculosis. Infection is transmitted commonly through breaks in the skin that come in direct contact with pus or fomites (such as shears and feeders) contaminated with pus, and it can occur at any age. Two forms of the disease exist: an internal form and an external form. Internal abscesses are hard to identify before death; however, they can lead to chronic weight loss and poor production. External abscesses form in superficial lymph nodes and contaminate the environment with large amounts of infectious pus when they rupture. Treatment is not considered effective, and organisms can remain viable for months in the soil. External abscesses should be cultured to confirm disease, and animals with obvious swollen lymph nodes or abscesses should not be introduced into the herd.

Clostridium tetani infection (tetanus) is most likely to occur after procedures such as castration and disbudding, or through contamination of wounds. Kids should be vaccinated against tetanus before or immediately after these procedures.