COCCIDIOSIS in lambs has a significant economic impact on flocks as, apart from the obvious losses as lambs die, there are hidden losses due to reduced growth rates even in lambs that may not have shown obvious clinical signs, said NADIS in a pre-lambing briefing.


Coccidiosis in lambs occurs when susceptible 4-8 week-old lambs take in pathogenic coccidia oocysts (eggs) by mouth. There are many types of coccidia but only two (eimeria ovinoidalis and eimeria crandallis) cause disease in sheep in the UK.

In any new season, the initial source of oocysts is from ewes shedding low numbers and from the previous season's lambs as oocysts can survive overwinter on pastures or in buildings.

Once new season lambs start eating oocysts, there is a dramatic multiplication of coccidia inside the lambs so that millions more are passed in the faeces and this dramatically increases environmental contamination.

Lambs most at risk of disease are those that have not had the chance to develop immunity but are exposed to high contamination - eg five-week-old lambs that are moved into a field where older lambs have been.


- Diarrhoea (which may contain mucus or blood)

- Straining,

- Abdominal pain,

- Weight loss

- Death

Clinical coccidiosis is most often seen in lambs aged 4-8 weeks old. It is not common in animals over three months old, however, the knock-on effects of sub-clinical disease, such as poor growth rates, may be apparent in older lambs.


Examination of a faecal sample at the laboratory with speciation to check whether the coccidia present are pathogenic (ie, that they are one of the two types that cause disease in sheep)

A pooled sample from 10-15 lambs that are 4-12 weeks old would be appropriate with veterinary post-mortem examination of dead 4-12 week old lambs.

It should be noted that cocci causes similar symptoms to nematodirus and occurs in similar aged lambs so it is important to have an accurate diagnosis.


Use toltrazuril, or diclazuril dosed at 1ml per 2.5kg lamb body weight, given by mouth.

Treat the whole group immediately that coccidiosis is diagnosed in a single lamb in a group, which should be given to all lambs over three weeks old in that group. It may be necessary to repeat the diclazuril dose after three weeks.

Group treatment in the face of expected high coccidia challenge. There may not yet be lambs showing clinical disease, but history and screening have indicated that lambs will be exposed to a high level of oocysts.

(NB: diclazuril has no residual activity, so the timing of treatment is critical and it is rarely appropriate to be used on the day of turn-out. When susceptible lambs are moved onto contaminated land, the product should be given 10-14 days later and it may be necessary to give a second dose three weeks after the first. Toltrazuril has a longer duration of action, so one dose is all that is necessary and timing is less critical but the ideal timing of treatment has been shown to be a week after turn-out onto contaminated land or a week before expected clinical disease.

Other methods included a decoquinate mixed into the lamb creep at a rate of 1mg/kg body weight per day for at least 28 days - but each 10kg lamb must ingest 100g of creep a day to maintain adequate levels, which may be an issue for a sick lamb. Decoquinate is active only in the small intestine which means that lambs may still shed oocysts

It is not appropriate to medicate ewes, as they are unaffected by coccidiosis and they are not the only source of oocysts, plus there are benefits to very young lambs having access to low levels of coccidia.


Understand the disease so that you can avoid high risk situations such as ewes and lambs being housed for a long period before turn-out; or young lambs (4-8 weeks old) moved into fields or buildings where older lambs have already been this year; or young lambs are put into fields that were used by lambs that had coccidiosis last year or that were used by a different flock last year; or where lambs can defaecate into food or water troughs

You can also get a better handle on the coccidia status of your flock by sending samples from 4-12-week-old lambs to the vets for coccidia speciation and by getting the vet to post-mortem any lambs that die.

If you know that your lambs will face a high coccidia challenge then consider treatment as outlined above. Studies have shown that, in the face of a challenge, lambs treated with diclazuril or toltrazuril shed fewer coccidia oocysts, have less or no diarrhoea and grow faster than untreated lambs.

A single dose of toltrazuril is more effective at reducing the numbers of oocysts shed than a single or double dose of diclazuril, resulting in less contamination of the pasture and thus a lower challenge facing the next batch of lambs.