With no current effective treatments, it has become increasingly important to understand the disease process and proactive measures to decrease the risk of blackhead entry into your flock.
Cause of blackhead?
It is a parasitic disease caused by Histomonas meleagridis which results in clinical disease in numerous poultry species (turkeys, chickens and quail).
What does blackhead look like?
Blackhead is a disease that primarily affects turkeys and will begin to present itself around 7-12 days after exposure. The birds will appear lethargic, droopy wings, head drawn towards its body, and sulfur coloured droppings. Often in chronic cases the birds will begin to lose significant muscle mass. Mortality can be quite variable, but in some instances if left untreated can reach up to 100%. The necropsy lesions can be quite profound and help guide in making a quick diagnosis. There can be enlargement of the ceca with thickening of the wall and yellow caseous cores. The liver can contain multiple ‘target’ like lesions that will reach sizes of 1-2 cm in diameter. It is very important on any suspicion of illness to submit birds to your local laboratory and contact your veterinarian immediately.
(see document at bottom for pictures)
How is it transmitted?
- Ingestion of cecal worm eggs containing Histomonas meleagridis.
- The ingestion of earthworms that are carrying cecal worms infected with Histomonas meleagridis.
- The most common source of horizonal transmission within an infected flock is cloacal drinking. This is a natural process of when a turkey surveys the litter environment by intaking material to help build the immune system. Unfortunately, if the turkey is sitting on Histomonas contaminated feces it will allow easy access of the parasite to the gut wall.
- The direct ingestion of contaminated feces within a barn or pasture. This is an unlikely initial source of infection and often only marginally contributes to the spread within a flock.
- Rapid diagnosis and veterinary confirmation (by gross lesions, gut scraping and microscopy).
- Use fencing to make pens in the barn with the intention of segregating the sick and healthy birds. This will also act to slow down the spread of disease within the barn.
- Cull all birds that appear depressed and lethargic.
- Apply hydrated lime to the litter and top dress the litter with fresh shavings.
- If possible, move the flock to a clean barn as soon as possible.
- If birds are at or near market weight plan emergency slaughter
- Communicate the diagnosis to the plant for the expectation of increased liver condemnations (product is not a risk to human health for consumers or plant workers)
- Intensive cleaning and disinfecting of the contaminated barn
- Increase biosecurity between flocks located on the same farm. This would include separate boots and coveralls at every barn entry.
- Work with your Veterinarians to develop a deworming program
- Apply salt to the perimeter of the barn to minimize the risk of earthworms gaining access inside and evaluate the seals of all barn entry points. This is especially important after recent rainfalls as earthworms will prefer to move on wet cement as it will allow them to move much faster than in the dirt.
The Canadian Association of Poultry Vets was successful in working with Health Canada to achieve an emergency drug release for Paramomycin which is a product used in Europe to treat Blackhead. The product will be held in a stockpile for access by veterinarians as needed. This process is on-going but expect to have the product available for emergency use within the next few months.
Blackhead can be a devasting disease and hopefully with taking the necessary precautions you can lower the risk of infection on your farm.