Coccidiosis in Turkeys

The life cycle of Eimeria species consists of three stages, one occuring outside the host (sporogony), two others (schizogony/asexual and gamogony/sexual) in distinct sections of the GI tract. Coccidia have a very high degree of host specificity, and even parasitise specifically certain zones of the GI tract, e.g., E. meleagrimitis parasitises the upper and middle intestine, whereas E. adenoeides multiplies in the caecal pouches.

In turkey there are three economically important Eimeria spp that infect primarily growing turkeys between 3 and 10 weeks of age.

• E. meleagrimitis
• E. adenoeides
• E. gallopavonis (in process)

Differential diagnosis of each species depends upon the zone of the intestine parasitised, the gross appearance of the lesions and the morphology of the oocysts.

JM Répérant in France developed a diagnostic lesion scoring method based on the visual inspection and severity of coccidiosis lesions. However, in turkeys the appearance of the intestinal coccidiosis lesions is not as typical of the infecting Eimeria spp in chickens and as a consequence, lesion scoring is more useful for laboratory infection models that for field conditions.

Moreover turkey coccidiosis can be very insidious. Therefore, very young, sick turkeys with diarrhoea and actively shedding oocysts should be treated for coccidiosis!

Depending on the dose and the pathogenicity of the infecting species, coccidiosis causes clinical disease with considerable associated economic damage, i.e., mortality, reduced weight gain and increased feed conversion. Coccidiosis infections in turkeys are often multifactorial with other intestinal triggers involved, e.g., hemorrhagic enteritis.