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Introduction
Coccidiosis in turkeys is common, but often goes undiagnosed as the lesions and clinical signs are often less obvious than in chickens. Lesions also are quick to resolve and so upon necropsy they are undetectable.
Disease is mostly apparent in young poults, with turkeys older than 6- 8 weeks seemingly very resistant. All coccidia species are thought to be common and exposure is thought to occur at an early age and resistance develops. Morbidity rates are high in young poults as the disease spreads through the group and mortality rates vary largely with species of Eimeria, concurrent infections, age and the size of the coccidia burden. Mortality when infected with pathogenic Eimeria is common in young poults, but older turkeys usually succumb to illness only.
There are seven Eimeria species currently known to have been found in turkeys. Isospora and Cryptosporidium species are also found in the turkey.
Each specie has predilection sites and variable pathogenicity, however only two are important pathogenically.
Eimeria in the caecum cause petechial haemorrhages and caseous caecal cores as well as mucous secretion.
Eimeria in the anterior and mid-intestine cause necrotic enteritis and petechial haemorrhages.
Clinical signs
Typical signs include diarrhoea, which may be watery, mucoid or blood-tinged depending on the predilection site of the infecting organism. General depression will ensue in the flock with signs such as ruffled feathers, reduced appetite and huddling.
Diagnosis
History and clinical signs are often used as a presumptive diagnosis, but a post mortem examination of a sick bird (which will be sacrificed for this purpose) is undertaken to confirm this. Gross lesions on the caecum and mid intestine are stereotypical of coccidiosis, but mucosal scraping for microscopic examination should be taken to identify coccidia with certainty.
Treatment and Control
Control of coccidia in turkeys, like broiler chickens, is intensive. Poults will be fed a prophylactic anti-coccidial drug for the first 7 - 8 weeks of life and then removed from this usually two weeks prior to slaughter so no residues are present in the meat. Approved prophylactic drugs include amprolium, monesin and halofuginone.
Some farmers, primarily in the USA, are trying an inoculation for poults from the age of 1 - 7 days. this is spread in the water and a mild infection of coccidiosis then ensues. It is then hoped these birds will develop and immune response, so the use of continued drugs is not needed. This program has been used with moderate success at this current time.
Should an outbreak occur which requires treatment, amprolium or some sluphonamides can be given to the flock via the water supply; often with moderate effect, hence prevention is better than treatment in this case.
References
Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition) Merial
Jordan, F, Pattison, M, Alexander, D, Faragher, T, (1999) Poultry Diesease (Fifth edition) W.B. Saunders
Randell, C.J, (1985) Disease of the Domestic Fowl and Turkey, Wolfe Medical Publication Ltd
Saif, Y.M, (2008) Disease of Poultry (Twelfth edition) Blackwell Publishing