Guidelines for treating coccidiosis can sometimes be open to interpretation. Louise Hartley asks vet Fiona Lovatt to explain the research, risk factors and treatments.
When the stress of lambing is over, all attention is focused on keeping every lamb alive and thriving. Coccidiosis mainly affects intensively reared young lambs but can also be found at pasture. Although mortality rates are low, it can have a big impact on productivity. Understanding the disease and knowing then to treat lambs is crucial to its effective control.
There are up to 15 different types of coccidia found in sheep, but only two types actually cause disease.
Lambs are at risk if one or both of these types are present on farm and it is strongly recommended that farmers find out if and what type of coccidia they have by testing, explains Dr Lovatt, independent sheep consultant and senior vice president of Sheep Veterinary Society.
It is, however absolutely essential not to rely solely on ‘a high cocci count’ in a faecal sample, as there can be ’non-harmful’ coccidia present with no disease consequences.
Samples from 10 to 15 lambs aged between three to 12 weeks old should be provided to the vet for testing which should include ‘speciation’.
Dr Lovatt says: “Sample results from the last three years show it is unusual for coccidia to cause disease in lambs over three months old (although at this stage we do still see the ongoing effects of poor growth rates caused by sub-clinical disease).
“Ask your vet to consider undertaking a coccidia-risk-assessment on the farm. There are specific questions which need to be answered, such as whether coccidia has been diagnosed in certain fields in previous years or if coccidiosis has been found in post-mortem examinations of lambs up to three months old.
“Certain practices can increase the risk of coccidiosis - these include housing ewes and lambs for a prolonged time before turnout, putting young lambs in fields where older lambs have previously been and lambs defecating into feed or water troughs.”
Research into coccidiosis at the Royal Veterinary College in the late eighties showed lambs mounted a strong immunity to the disease and did not show clinical signs at any age if they were pre-exposed to coccidia before four days old. Low level coccidia exposure any time before three weeks old was also beneficial. This is one of the reasons why the medication of ewes is particularly unhelpful in preventing lamb coccidiosis, says Dr Lovatt.
"High risk lambs may need medication but timing of treatment is crucial [see fact box]. It is generally unnecessary to treat lambs less than three weeks old, and doing so may adversely affect the development of immunity and waste the treatment."
Batching lambs by age and understanding the coccidiosis risk to different groups on different parts of the farm can be very helpful.
"Early in the season, lambs will be at lower risk and may not need treating at all or at least until they are six weeks old. Later through the season the challenge will have built up and younger lambs will be at risk.
"Coccidiosis can be a challenging disease but we have a good understanding of the risks and good products available for its treatment and control. Talk with your vet about your specific farm situation, taking appropriate samples for speciation and appropriate control options."
A single dose is effective. Treat immediately if symptoms are seen and treat all the other lambs in the group. To prevent symptoms and subsequent losses treat a week before clinical signs are expected (this usually means one treatment at between three and six weeks old).
Research has shown it to be the most effective in reducing losses and pasture contamination due to shedding.
Effective but with short duration of action, so treatment timing is crucial. Treat immediately if clinical signs are seen and treat all the other lambs in the group. To prevent symptoms and subsequent losses, treat lambs just before clinical signs are expected.
Never treat lambs under three weeks old and it is often appropriate to treat 10 to 14 days after lambs are put on high risk contaminated fields. Treatment may need repeating two to three weeks later.
Effective only as long as lambs are eating sufficient creep, therefore not appropriate in many situations and certainly not when lambs are sickly, possibly due to Nematodirus.