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Coccidiosis in Lambs

Rose Young BVM BVS MRCVS, Molecare Veterinary Services

Coccidiosis or “cocci” as it’s usually known, is a parasitic infection which causes disease in young lambs and calves. Its cause is a small, single-celled organism which inhabits the intestines of many different animal species, and can cause damage to the lining of the gut resulting in weight loss, failure to thrive, diarrhoea and death if severe. Cocci can be found in the intestines of healthy, adult animals in relatively low numbers without causing any problems, and a certain amount of exposure to cocci in youngsters is normal, and in fact beneficial to help generate good immunity in later life. Disease occurs when young, susceptible animals are exposed to huge numbers of cocci in the environment, and develop overwhelming infections that their young systems are unable to cope with.

Cocci oocysts (eggs) are shed into the lamb’s environment via the dung of other infected sheep. Often older animals (adult ewes or older lambs) act as the original source of infection, but once young lambs become badly affected they begin to shed vast numbers of eggs and an outbreak can really take hold. The more tightly stocked the lamb environment, the quicker cocci can build up; so this is a disease which tends to affect early lambers, and indoor, more intensive systems. Problems can develop in outdoor systems too, especially in “hotspot” areas where lambs spend a lot of time, such as around creep feeders or in gateways. Higher environmental temperatures will also increase the number of viable eggs on the ground, and cocci eggs are able to overwinter on pasture, so can affect lamb crops one year to the next.


Cocci can start to affect lambs from around three weeks of age, when immunity from the ewe’s colostrum begins to wear off. Of the eleven species of cocci found in sheep, only two are pathogenic (cause disease) and all have a period of infection (pre-patent period) during which the disease is active but eggs are not shed, usually between two and three weeks. This means that simple faecal egg counts are not usually the best way to diagnose an issue with coccidiosis. Sometimes cocci diagnosis is actually based on the history of the farm, and the likelihood of exposure of high numbers of cocci to the lambs.

Risk factors include:

Indoor management with high stocking rates

Mixed lamb age groups (likely with extended lambing periods)

Poor hygiene in sheds (or around feeders or gateways)

Repetitive use of the same pasture for lamb turnout each year

Other stressors such as poor nutrition, inclement weather or weaning

A history of coccidiosis in the same system the previous year

If symptoms in individuals do develop, you will likely see

Poor growth rates, poor appetite and a tucked up/scruffy appearance

Dung staining around tails and legs, diarrhoea which sometimes contains blood flecks

Collapse and death if severe, or worsened by presence of other disease (worms, fluke etc.)


If we diagnose cocci in a lamb crop, treatment usually consists of one of three licensed products containing either diclazuril, toltrazuril or decoquinate. Two are oral drench products which we administer either in the face of an outbreak or as a strategically timed preventative. The third is a feed additive which we can use as a routine preventative on farms where it is not possible to reduce the risk of exposure to the lambs.

If you suspect a new problem with cocci or have treated for it in the past; your vet or SQP can help to advise you on a treatment regime specific to your farm. The timing of cocci treatment is vital in order to provide treatment for lambs with symptoms, but also allow a low level of exposure and subsequent immunity to develop. Usually, it will affect all of the lambs in a group, even if only a few are showing signs; in most cases it is best to treat the whole group.


If practical, prevention is always better than having to resort to giving costly medications after losses have already occurred.


Manage lambing in as tight a block as possible to reduce time for cocci build up in spring

Under vet guidance, use medicated feed for ewes to reduce cocci egg output at lambing time

Cover all the basics of lambing, particularly good colostrum and good hygiene


Turn out ewes and young lambs onto clean grazing, which has not carried ewes over winter or particularly young lambs the previous year.

If indoors, try to batch lambs into age groups to reduce transmission from older to younger.

Clean out lambing sheds and mothering pens regularly, the more often the better.

If outdoors, move feed troughs or creep feeders regularly to reduce ground contamination.

Use a drench at around 3-4 weeks of age or before the known high risk period to prevent severe infection developing.

Under vet advice, use an in-feed treatment in creep to cover lambs during the whole risk period.

Coccidiosis also affects calves, the disease process in both species is similar. Always get in touch with your vet or SQP for advice on managing cocci to maximise your productivity.

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