The document discusses histomoniasis (blackhead), primarily affecting turkeys and caused by the protozoan Histomonas meleagridis, leading to serious liver and cecal lesions. The disease can result in high mortality rates in young poults and exhibits clinical signs such as yellow droppings and weight loss. Diagnosis relies on identifying lesions, while treatment involves isolation and medication, with preventative measures including separating turkeys from chickens and controlling cecal worms.

1. University of Mosul
College of Veterinary Medicine
Department of Pathology and Poultry
Disease
Black Head
Prepared by MSc student
Mohammed Sayfaden
Supervisser
Dr. Mohammed Ghasan

2. Histomoniasis
(Enterohepatitis, Blackhead)
• Histomoniasis is caused by the protozoan
mainly characterized by ulceration and
inflammation of the cecal walls,
engorgement of the ceca with large
caseouse casts, inflammation of the
mesenteries, and extensive focal necrosis
of the liver.
• Most important in turkeys.

3. CAUSATIVE AGENT
• Histomonas meleagridis - a one-celled
organism/parasite
INCUBATION PERIOD
• From 7–12 days and Death may occur 11–14
days post infection (PI)

4. COURSE OF DISEASE
• Subacute: 10 days to 2 weeks
• Chronic: Several weeks
METHOD OF SPREAD
• The common cecal worm, H. gallinarum, is the only
worm known to serve as an intermediate host.
• Direct contact between susceptible and infected birds.
• Earthworms can serve as transport hosts in which
heterakid eggs hatch and survive.

5. Heterakis gallinarum Heterakis eggs

6. MORTALITY
• Poults - may reach 80 to 90% when
affected before 4 weeks of age
• Older poults - 20-25% or less
• Chicks and chickens - mortality varies

7. CLINICAL SIGNS
• Sulfur colored droppings –
yellow, foamy
• Cyanotic head (turkeys)
• Old birds lose weight
• Dropping of the wings, head down close to
the body or tucked under a wing, and anorexia.
• Sick birds tend to huddle together. By 6–12 days PI,
turkeys become emaciated.
• Chickens may be mild drooping feathers, morbidity,
closed eyes, and a drop in egg production in layers

8. Typical liver lesions
round sunken lesions

9. Cecal lesions
cheesy core

10. Multiple necrotic nodules in
the liver and caseouse cores in ceca

11. DIAGNOSIS
SUGGESTIVE DIAGNOSIS
• Typical lesions in ceca and liver.
POSITIVE DIAGNOSIS
• Cannot isolate or propagate - will see
causative agent on histo in liver tissue

12. Histomonads in liver

13. TREATMENT
• Separate sick birds.
• Metronidazole 250 mg/gal-5 days.
• A liquid form is used in pet birds.
PREVENTION
• Separate turkeys and chickens
• Control cecal worms
• Continuous medication