In this article, the focus is on diseases and parasites affecting sheep and goats. Since most diseases and parasites are common to both species, they will be addressed together.
Wastage due to diseases and parasites is a significant source of economic loss and one of the main barriers to the development of sheep and goats. The incidence of disease increases when poor nutrition reduces the animals’ resistance. Poor sanitation and hygiene also negatively affect the health performance of small ruminants.
In traditional village husbandry systems, 25-50% of lambs or kids born are lost. Among adult animals, annual mortality ranges from 14-20%.
Classification of Diseases in Sheep and Goats
There are three categories of diseases affecting sheep and goats:
1. Infectious Diseases
Infectious diseases include pest des petits ruminants (PPR), contagious caprine pleuro-pneumonia, and haemorrhagic septicaemia.
2. Non-Infectious Diseases
Non-infectious diseases refer to various metabolic disorders.
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Some Common Diseases and Parasites in Sheep and Goats
1. Pest des Petits Ruminants (PPR)
PPR is a major disease affecting small ruminants throughout tropical Africa. Goats suffer more than sheep from the disease. PPR is caused by a virus similar to the rinderpest virus.
Signs: Fever, followed by watery eyes, nasal discharge, necrotic lesions on the buccal mucosa, and diarrhea.
Treatment: Systemic antibiotics, notably long-acting terramycin.
2. Enterotoxaemia
Enterotoxaemia is a serious disease of sheep and goats caused by the absorption of toxins produced by bacteria in the intestines. Normally harmless in small numbers, these bacteria multiply rapidly when there is digestive upset, producing large amounts of toxins. The disease is often associated with animals in good condition that graze on lush grass or green crops.
Signs: Abdominal pain, severe diarrhea, and dullness. Animals usually recover.
Prevention: Avoid sudden changes in feed without an adaptation period.
Control: A vaccine is available to protect susceptible animals.
3. External Parasite Infestations
Mange is common but does not cause major problems for the animals. Flies and lice are also commonly found on sheep and goats, but serious issues only arise when their numbers become excessive.
Prevention: Vaccinate young animals and, if possible, the entire flock annually with the tissue vaccine used to prevent rinderpest.
4. Anthrax
Anthrax is an acute septicaemic disease caused by a highly resistant organism, Bacillus anthracis. Animals become infected through soil contaminated by the carcasses of infected animals. The bacteria survive in the soil as spores, which are ingested by animals.
Anthrax is usually fatal, with death occurring within 24 hours. Recovery is rare.
Diagnosis: In dead animals, the whole carcass and organs appear blackish, especially the spleen, which swells and releases a thick, blackish liquid when cut. Anthrax can be transmitted to humans, so care is necessary during post-mortem procedures.
Control: Carcasses, including the skin, should be destroyed, either buried deeply in quicklime or burned.
Prevention: Vaccinate all animals, preferably before the rainy season, with a subcutaneous injection of the recommended vaccine dose.
5. Ticks
Ticks are a serious external parasite because, in addition to causing irritation and anemia, they can transmit various diseases that require laboratory tests for diagnosis.
Control: Regular dipping or spraying with acaricides helps control external parasites.
6. Foot-Rot
Foot-rot is a common and serious disease affecting sheep and goats. It is caused by the growth of specific fungi in the feet, with other environmental organisms contributing to the infection. The causative fungi thrive in wet conditions and become dormant during the dry season.
Signs: Lameness, swelling, and pain in the frog and coronet areas of the foot. Discharge may be present between the hooves. Without treatment, the condition can deteriorate, and the animal may die.
Prevention: Keep animals away from wet, muddy, or marshy pastures. Ensure housing quarters are well-drained.
Control: Foot-baths containing a solution of copper sulphate and an antiseptic are effective. Clean the affected area and remove necrotic parts. Isolate the affected animal in a dry place for a few days.
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7. Mastitis
Mastitis is the infection of one or both udders by microorganisms usually found in the environment. While not life-threatening, mastitis often results in the loss of the affected udder, reducing the ewe’s productivity.
Signs: The affected udder is red and painful. Milk turns into a serous liquid, which may contain pus or be blood-stained. Lambs or kids stop nursing from the affected udder. Abscesses may form, and a mixture of milk, pus, and blood may ooze from the area.
Prevention: Keep sheep and goat houses clean, and remove sharp objects that could cause injury to the udder.
Control: Infuse an antibiotic preparation into the udder after it has been emptied. Systemic antibiotics should also be administered.
8. Parasite Gastro-enteritis
This disease is caused by a massive infestation of the abomasum and intestines with small parasitic worms. Kids are particularly susceptible, while adults are more resistant.
Signs: Progressive loss of condition, sometimes leading to emaciation. Appetite usually remains good until late in the disease.
Prevention: Avoid restricted grazing, as it leads to a buildup of infective larvae. Most larvae die within six weeks of hatching, so resting pastures for this period reduces larval concentration.
Control: Regular use of anthelmintics is recommended.
This article covered various diseases that can affect sheep and goats on the farm, including signs, preventive measures, and control methods. A significant part of disease prevention depends on the actions taken by the keeper or rearer to reduce disease incidence in the herd.
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