Intro to Histomonas meleagridis 

1. WELLCOME
Histomonas meleagridis

2. Introduction
• First report in Rhode Island (USA) in 1893 in Turkeys.
• Histomonas meleagridis is an anaerobic protozoan parasite.
• It is an anaerobic , pleomorphic protozoan, and can exist in two
forms, amoeboid and flagellated.
• Within the tissue, it is present as an amoeboid form (8–30 μm in
diameter) .
• In caecum, it lives as an elongated flagellate form (8–15 μm in
diameter).

3. Cont.
• It causes infectious enterohepatitis, or histomoniasis (blackhead
diseases).
• It infects a wide range of gallinaceous birds including chicken, turkeys,
pheasants, peafowls and quails.
• It is most deadly in turkeys (80%-100%).
• Chickens are typically asymptomatic carriers.

4. Transmission
• It is transmitted by another caecal parasite, the nematode Heterekis
gallinarum.
• Earthworm can act as Paratenic host.
• In turkeys, transmission by direct cloacal contact with infected birds

5. Clinical Sign & Symptoms
• Signs of histomoniasis are apparent in turkeys 7–12 days after
infection and include:
• Prolonged standing
• Closed eyes
• Emaciation
• Drooping head and wings
• Ruffled feathers
• Sulfur-colored droppings

6. Postmortem
• Primary lesions as caecal ulceration (3–4 days after invasion).
• Necrotic lesions in the liver (6–8 days after infection)
• Lesions are also seen in other organs, such as kidneys, spleen, and
pancreas.

7. Diagnosis
• Clinical signs.
• The liver and caecal lesions are pathognomonic
• Examination of cecal/liver contents under a microscope
• PCR
• Histopathologic examination

8. Treatment & Prevention
• There are no approved treatments or vaccines.
• Turkeys should not be raised with other galliformes such as chickens.
• Control earthworm.