Histomonas

Question 1

What is the main species of Histomonas: (1)

Answer 1

Histomonas meleagridis

Question 2

What disease does H. meleagridis cause:

Answer 2

• Black head disease
• Mucopurulent typhlitis
• Purulent hepatitis

Question 3

What is the vector of H. meleagridis:

Answer 3

Heterakis gallinarum, a nematode/worm that occupies the ceacum

Question 4

What is the Life cycle of H. meleagridis:

Answer 4

1. Flagellated form of Histomonas in the ceacum is ingested by Heterakis which may pass into their eggs
2. The infected Heterakis eggs are eliminated into the environment with feaces (can live up to 2 years) Exogenous
3. The infected eggs are then ingested by the host
4. The Heterakis egg then hatches in the caecum and Histomonas is liberated
5. The flagellated form in the ceacal lumen changes to tissue invasive form, penetrates and multiplies in the caecal wall
6. Eventually entering the blood vessels where it metastasize to live

Infected Heterakis worm can also be ingested

Question 5

What are the diagnostic methods for H. meleagridis:

Answer 5

1. Clinical signs
2. Pathomorphology
3. Histopathology
4. Cultivation
5. Serology
6. PCR

Question 6

What is the Morphology of H. meleagridis:

Answer 6

Caecal lamina stage: 8-12 μm, varies in shape, one flagella
Tissue invasive stage: 8-17 μm, spheroid, no flagella but has pseudopodia
Spheroid resting stage: within the Heterakis eggs 3 μm

Question 7

Can free Histomonas live in the environment:

Answer 7

No, it needs to be in Hererakis egg (Paratenic host)