histomonosis

Histomonosis, also known as blackhead disease, is an infectious disease that primarily affects poultry. It is caused by the protozoan parasite Histomonas meleagridis. While turkeys are the most susceptible species and often experience severe illness and high mortality, chickens, pheasants, and other gallinaceous birds can also become infected.

The parasite is typically transmitted through the droppings of infected birds. Earthworms can act as paratenic hosts, ingesting the parasite from contaminated soil and then being consumed by birds. The parasite then infects the ceca (a part of the digestive tract) and the liver.

Symptoms of histomonosis in turkeys can include lethargy, ruffled feathers, drooping wings, loss of appetite, and a characteristic sulfur-yellow discoloration of the droppings. In chickens, the disease is often less severe, and many birds may show no outward signs of illness, though some may develop liver lesions.

Diagnosis is usually made based on clinical signs, post-mortem examination revealing characteristic lesions in the ceca and liver, and microscopic identification of the parasite. Treatment options are limited, and prevention through good sanitation, biosecurity measures, and avoiding co-mingling of different poultry species is crucial. Certain medications can be used for treatment and prevention, though their availability and efficacy may vary. Control strategies often focus on preventing exposure to the parasite and its vectors.