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‘Less serious’ Eimeria species can be pathogenic in chickens

Some of the Eimeria species that affect chickens but are thought to be less serious can, in fact, be pathogenic, with some resulting in mortality, Steve H. Fitz-Coy, PhD, said at the 2011 annual Poultry Science Association meeting.

E. mitis, for instance, doesn’t produce lesions, but causes growth suppression and cessation in egg production. Its prevalence is less than 15%, said Fitz-Coy, a scientist for Merck Animal Health and one of the world’s leading experts on coccidiosis in poultry.

E. mivati is the most pathogenic of the lesser species and leads to growth depression in broilers as well as cessation of egg production and mortality in susceptible birds. Signs are watery and mucoid droppings with a tinge of blood; gross lesions are white spots with a “star burst appearance” in the upper small intestines. Mortality can occur and may vary from 10% to 40%. The prevalence of E. mivati in the US is estimated to be 20% to 30%, he said.

One of the most prevalent Eimeria species in chickens is E. acervulina, which can cause severe growth depression, impaired feed efficiency and cessation in egg production. Clinical signs are watery, viscid and mucoid droppings. Gross lesions are white transverse bands that, in severe infections, may coalesce in the upper third of the small intestines, Fitz-Coy said.

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