Histomoniasis outbreak in free-range chickens in semiarid Paraíba, Brazil

Resumo

We describe an outbreak of histomoniasis in free-range chickens (Gallus gallus domesticus) in the semiarid region of Paraíba State, Brazil. Juvenile chickens aged approximately 48 days showed disease over a 15-day period. Seven of 16 chickens showed yellow, watery stool, anorexia, lethargy, and death within 3-5 days of clinical illness. The mortality rate was 43.7%. The chickens were raised in a backyard with 12 adult birds that remained healthy. None of the chickens were vaccinated or dewormed. A necropsy on one deceased bird showed lesions confined to the cecum and liver. The left cecum was distended and had yellow, slightly elevated areas on the serosa. The liver was reddened with centrally depressed areas surrounded by a pale halo, which were distributed throughout the capsular surface and extended deep throughout the parenchyma. Microscopically, typhlitis and pyogranulomatous necrotizing hepatitis associated with numerous intralesional Histomonas trophozoites was observed. The birds were administered metronidazole and albendazole, which effectively controlled the histomoniasis. Although histomoniasis is rare in free-range poultry, it can occur and cause high mortality and significant economic losses.