Field visits at two different farms suggest a correlation between commercial turkey flocks having increased mortality from blackhead disease (histomoniasis) if they suffered from poor poult quality at placement and coccidiosis prior to 6 weeks of age. Both cases were all-in/ all-out flocks with curtain sided houses and received a coccidiosis vaccine on day of hatch. Farm I, 2018 : Poults from different hatcheries were placed in 2 houses on the same farm (Houses 1 and 2). House 2 had poults considered poor quality and suffered from mortality associated with coccidiosis at 2 and 4 wks of age. At 8 wks, blackhead disease was diagnosed in both houses based on necropsies. House 2 had mortality of over 2,000 poults and the subpopulation of poults necropsied had gross lesions characteristic of histomoniasis. Gross lesions associated with blackhead disease were only found in 8 poults in House 1, which was populated with good quality poults and did not have mortality associated with coccidiosis. Farm II, 2020: Poults were delivered from the same hatchery onto a 3-house farm (Houses A, B, and C). House C had poults that were considered poor quality and had mortality associated with coccidiosis at 3 wks of age. At 8-9 wks, House C had mortality approached 1,000 birds with all necropsied poults having clinical signs of blackhead disease. Houses A and B were populated with good quality poults and had no mortality due to coccidiosis or blackhead disease. The similarity of these two cases suggest that poult quality at placement coupled with coccidiosis prior to 6 wks of age can influence the severity of blackhead disease in commercial turkey flocks.

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