Coccidiosis - Sheep


There are 11 different Coccidia species in sheep, although only two are of clinical significance. These are the highly pathogenic Eimeria ovinoidalis, which parasitises the caecum and colon, and Eimeria crandalis, which has varying pathogenicity and parasitises the small intestine and colon.

Disease is usually seen in lambs under six months old. They are usually in good body condition at the onset of the disease. There is a two week pre- patent period for this parasite, so disease can spread in the flock relatively quickly. As with all coccidial diseases, they are usually caused by over-crowding and unhygienic conditions.

Disease is spread faeco- orally. Oocyts from ewes (immune carriers) accumulate in poorly managed litter or around feed and water troughs. Lambs born early in the year amplify the parasite problem increasing the parasite risk to lambs born later in the year. This is because there is a high number of oocysts deposited by newly infected animals.  

Clinical Signs

Diarrhoea is the main clinical sign. It is often of sudden onset and may appear grey and be foul-smelling.


Clinical signs, history and signalment of the lambs are highly indicative of the disease.

Faecal samples are a vital diagnostic tool. Identification of the oocysts in faeces by microscopic examination should be performed and the slide should be stained to see if other parasites e.g. cryptosporidium or neospora may also be present. Mixed infections complicate the diagnosis as oocyst differentiation is difficult. Also, affected lambs may die before oocysts are found in the faeces.

Post-mortem diagnosis is difficult as there are many non-specific findings; other non-pathogenic species can cause papillomatous mucosal growths.

Treatment and Control

Treatment with diclazuril or decoquinate, plus electrolyte solution for re-hydration.

Control measures include improving husbandry, reduce overcrowding and decrease stress. Improve hygiene by dagging (clipping off clumps of dried dung stuck to the wool) ewes and avoid mixing lambs of different ages.

Preventative measures include creep feeding lambs with decoquinate or oral dosing with diclazuril when lambs are 4-6 weeks. A second dose can be given after 3 weeks.

Coccidiosis - Sheep Learning Resources
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Fox, M and Jacobs, D. (2007) Parasitology Study Guide Part 1: Ectoparasites Royal Veterinary College

Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses Elsevier Health Sciences  

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