An outbreak of histomoniasis in turkeys infected with a moderate level of Ascaridia dissimilis but no Heterakis gallinarum.

Histomoniasis was diagnosed in a commercial turkey flock. All morbidity and mortality occurred in one house. Birds exhibited lesions characteristic for histomoniasis, and the diagnosis was confirmed by histopathologic examination. Affected turkeys were infected with moderate levels of Ascaridia dissimilis but not Heterakis gallinarum. Compression smears of hepatic tissues showed typical histotrophic phase Histomonas meleagridis, whereas cecal smears exhibited large numbers of Trichomonas gallinarum. A challenge experiment was conducted in which turkey poults were placed on contaminated litter. Although histomoniasis was not reproduced in the experiment, the birds did become infected with low numbers of A. dissimilis.