Toxoplasmosis causes occasional abortions in goats and sheep. The coccidia-like organism (toxoplasmosis gondii) first infects cats when they eat uncooked meat scraps, placentas and small rodents, and the infection can be passed on to goats if their feed supply becomes contaminated by cat feces, because recently-infected cats will shed oocytes (toxoplasmosis eggs) in their feces from 3 to 19 days. Kittens younger than 6 months of age are far more apt to shed oocytes than are adult cats. Toxoplasma oocysts have a tough outer shell and can survive in the environment in moist temperate conditions for 12-18 months. Once ingested the parasite multiplies within the goats or sheep and persists in cysts within the brain, heart and muscle.
Goats typically become infected by eating grass, hay and grain contaminated by cat feces. Sometimes abortion is repeated in the next gestation, but previously-infected goats are usually resistant to abortion or other clinical signs when challenged by the toxoplasmosis organism.
In pregnant small ruminants, if the parasite infects the animal for the first time, toxoplasma can cause disease in the placenta and the developing fetus. Infection early in pregnancy may result in abortion, whereas infection later in pregnancy may cause still birth, mummified fetus or birth of a live but weak kid or lamb.
The best prevention is by safeguarding feed supplies from cat feces, especially grain and mineral mixes that cats may use to defecate in, and to keep mangers clean by emptying them regularly.
When abortions caused by toxoplasmosis are diagnosed in goats or sheep, emphasis should be put on proper disposal of fetuses and placentas, the wearing of protective gloves when handling those items, and proper pasteurization of milk and cooking of meat.
There is an effective vaccine to prevent congenital toxoplasmosis in sheep which should be administered 3 weeks prior to mating. Unfortunately, the vaccine is not available in the US for small ruminants.
Toxoplasmosis may also be transmitted to humans from the ingestion of oocysts or from eating undercooked meat containing parasite tissue cysts. Pregnant women and immuno-compromised individuals are major risk groups and should also avoid contact with ewes at lambing time.
Publication date: Oct. 12, 2015
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