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Blackhead is a severe protozoan disease of turkeys and peafowls and also affects fowls and game birds. It is also known as entero-hepatitis and histomoniasis. The condition is characterised by caecal (blind gut) and liver lesions. Fowls tend to be more resistant to Blackhead and therefore should not be run with turkeys. Blackhead mainly causes deaths in birds 3 to 18 weeks of age and is probably the most serious disease confronting the turkey producer.

Scientific name

Histomonas meleagridis

Cause

Blackhead is caused by the protozoan organism Histomonas meleagridis.

• Damages the caecal wall
• Allow secondary infection to occur (Clostridium perfringens, Bacillus subtilis)
  
• Spread to the liver causing yellow droppings.

The caecal worm (Heterakis gallinae) is always present during blackhead outbreaks although can be present without blackhead occurring.

Histomonas can:

• Shelter within the egg of Heterakis
• Survive in the soil for up to four years within Heterakis eggs
• Spread via earthworms eating Heterakis eggs

Hence poultry houses can be difficult to clean up once they are infected.

Species affected

• Chicken
• Turkey
• Peafowl
• Game bird

Birds with lowered resistance due to factors such as fowl pox or nutritional diseases are more severely affected. It also seems that turkeys are more susceptible.

Symptoms

Blackhead is a disease of the caecum and liver.

1. Fowls

• Young chickens only (3-4 weeks old)
• Lethargy
• Weakness
• Drooping heads and wings
• Yellow droppings
• Muscle waste
• Death (10%)

2. Turkeys

• Young and older birds (usually 18-20weeks old)
• Weakness
• Ruffled feathers
• Soiled vent feathers (diarrhoea)
• Drooping heads and wings
• Bright yellow-sulphur droppings
• Darkened heads
• Death 2-3days following the first signs (up to 100%)

Turkeys are clinically affected about 10 days after infection and death occurs 2 to 3 days later with up to 100% mortality.

Post mortem findings

1. Caecum (blind gut):

• Haemorrhage
• Inflammation
• Thickening
• Ulceration
• Grey-yellow cheesy cores of necrotic (dead) tissue - often streaked with blood
  

2. Liver:

• This is more common with turkeys than with chickens
  Round, creamy-yellow depressions of necrotic tissue
  (pinhead size up to 1cm in diameter)

Transmission

The ingestion of Histomonas meleagridis is possible through:

• Contaminated droppings (in young birds)
• Contaminated caecal worms (Heterakis)
• Contaminated earthworms

Diagnosis

Compatible symptoms and post mortem examination

Similar diseases

1. Chickens

• Coccidiosis
• Heavy worm burdens
• Fowl cholera.

2. Turkeys

• Hexamitiasis
• Coccidiosis
• Cholera

Treatment and control

1. Management
Control of blackhead relies on the removal of caecal worm (Heterakis) eggs from the cycle and providing areas which are not heavily contaminated with the blackhead organism (Histomonas).

Major management factors:

• Keep turkeys and chickens apart ensuring drainage does not occur from chicken to turkey runs
• Caecal worm (Heterakis) control - suitable treatments are available
• Poultry should be brooded away from ranged turkeys and chickens - avoid contamination of ground
• Keep turkeys away from earthworms
• Ensure feeders and waterers are not contaminated with droppings and are moved to clean areas regularly

2 Medication
Little immunity is developed to blackhead although chickens are more resistant.

Successful control and treatment is accomplished by using drugs in combination with improved hygiene and management.

Preventative or curative medications may be administered through the feed or the water. Treatment in water is the most common method used, flocks normally being medicated for several days. The manufacturer’s directions should be closely followed.

TAG : Black_Head, Histomonas, Heterakis, Turkey, Fowl, Poultry, Bird, Chicken