Zoonotic diseases of sheep and goats (Proceedings)
Many sheep and goat producers are unaware of zoonotic diseases that can be passed from animals to man. Some zoonoses such as pinkeye or soremouth cause symptoms in the host animal so that the producer knows the animal is ill, but he may not realize that the disease could be transmitted to himself or his family. Other zoonotic diseases such as campylobacter enteritis or Q fever often do not cause symptoms in sheep or goats and the producer may not take adequate precautions to prevent transmission. Some zoonoses are transmitted directly from the animal to producer, while others are passed indirectly through fomites such as milk, meat, or fiber.
The incidence of rabies has steadily risen in the United States over the past few years due to epizootics in raccoons, skunks, foxes and coyotes. In 2001, 322 cases of rabies were diagnosed in California including one cat, one horse, 151 skunks, 2 foxes, 166 bats and 1 human. Between January and September 2008, there were 18 confirmed cases of rabies in skunks in Colorado when historically there have not been any cases of terrestrial rabies in that state. The DNA type of the virus involved in these skunk rabies cases indicated that they originated in Texas. Recently 24 dogs and cats adopted by soldiers in Iraq entered the United States without proper proof of rabies vaccination and at least one dog in that shipment died of rabies after importation. As the incidence of rabies in wild life has increased, the number of documented cases of rabies in sheep and goats has also risen and this has lead to an increased exposure for humans. In 1996, a rabid goat at a New York County Fair exposed more than 2700 people, and more than 400 people received prophylaxis at a cost exceeding $1000 per person.Public health officials stress the need to vaccinate domestic pets and livestock against rabies to provide a safety barrier between wild animals and man. There are currently four rabies vaccines licensed and labeled for use in sheep, but no vaccines are labeled for use in goats or camelids in this country. Each state veterinarian is responsible for determining what regulations apply for species for which there is no legal vaccine. Some state veterinarians have ruled that exhibited goats must be vaccinated, while others require exposed animals to be euthanized and tested for rabies. The CDC Compendium of Animal Rabies Prevention and Control recommends that all animals in petting zoos or for exhibition be vaccinated for rabies.
Reports of rabies in goats are rare, but the furious form of rabies appears to be more common. Symptoms in goats include aggressive behavior, excessive bleating, and salivation following an incubation period of one to five days. Cases of rabies in sheep appear more similar to rabies in cattle with an average incubation period of ten days. Rabid sheep exhibit muzzle and head tremors, aggressiveness, hyperexcitability, hyperesthesia, salivation, vocalization and recumbancy. There is no treatment for rabies in animals and treatment for exposed humans must be undertaken before clinical symptoms appear. With only one exception, all cases of rabies are fatal once clinical symptoms develop. When examining a sheep or goat with neurologic symptoms, remember that the affected animal might have rabies and wear disposable gloves to examine the oral cavity.
Campylobacter jejuni is the most common cause of food-borne illness in man and there are more cases of campylobacteriosis diagnosed each year than those of shigella and salmonella combined. One study revealed that approximately 45% of fecal samples from normal sheep and goats contained C. jejuni. The organism can be transmitted through fecal contamination of milk or by handling aborted fetuses and membranes. Many human outbreaks with sudden onset of severe nausea, cramps, vomiting, and fluid diarrhea have been traced to consumption of raw goat milk. Human infection with this organism can lead to Guillan Barre Syndrome, and pregnant women should not have contact with aborting sheep or goats. Food-borne illness caused by campylobacter is usually prevented through washing hands, wearing disposable gloves when handling aborted fetuses or membranes, and consuming only pasteurized milk and dairy products. Transmission of Campylobacter from animal to man can be reduced through improving sanitation of the sheep or goats. Clipping the hair on the udder and belly of lactating animals, frequent cleaning of the animal housing, thorough cleaning of the teats prior to milking, and use of pre-milking iodine dip help reduce transmission of this bacteria through milk. Use of disposable gloves and face masks during pen cleaning and assistance with birthing also reduces transmission of this agent. Herds that experience abortion due to Campylobacter jejuni should vaccinate prior to breeding, and there is anecdotal evidence that feeding chlortetracycline to pregnant sheep and goats may decrease the incidence of abortion due to this microbe.