blackhead disease turkey

Blackhead Disease in Wildlife: Causes, Symptoms, and Management

Blackhead disease, also known as histomoniasis, is a parasitic infection that affects birds and some other species, including turkeys, chickens, and game birds. The disease is caused by the protozoan parasite Histomonas meleagridis and is transmitted through the ingestion of infected materials, such as earthworms, slugs, and other insects. In this article, we will explore the causes, symptoms, transmission, diagnosis, treatment, and management of blackhead disease in wildlife.


The primary cause of blackhead disease is the protozoan parasite Histomonas meleagridis, which is prevalent in the soil and litter of poultry farms, game bird facilities, and wild bird habitats. The parasite can survive for several months in moist soil, making it a persistent threat to susceptible bird populations.

The parasite’s life cycle begins when infected birds, such as turkeys or chickens, pass the parasite’s eggs in their feces. The eggs are then consumed by earthworms or insects, which serve as intermediate hosts. When a healthy bird eats the infected earthworm or insect, the parasite moves into the bird’s gut, where it causes damage and produces lesions that can be fatal.


Blackhead disease is a significant threat to game bird populations, especially in areas where infected domestic poultry are raised near wild birds. It can cause significant economic losses for poultry farmers and game bird breeders due to mortality and decreased productivity.

The disease also has ecological implications, as it can reduce the population size of important game bird species and disrupt ecosystem dynamics. In addition, the spread of the disease can lead to public health concerns, as some strains of the parasite can infect humans and other animals.

Species Affected

Blackhead disease affects a wide range of bird species, including domestic poultry such as chickens, turkeys, and pheasants, as well as wild birds such as quail, grouse, and wild turkeys. The disease can also affect other animals such as peafowl, guinea fowl, and even some mammals, although these cases are relatively rare.


Blackhead disease is present worldwide, but it is more prevalent in areas where domestic poultry and game birds are raised near wild bird habitats. The disease is commonly found in North and South America, Europe, Asia, and Australia.


The transmission of blackhead disease primarily occurs through the ingestion of infected materials such as earthworms, slugs, and other insects. The disease can also spread from bird to bird through direct contact with infected feces or through contaminated water and feed.

Wild birds can contract the disease by consuming infected materials in their natural habitats, or they can acquire the disease from domestic poultry raised in close proximity to their habitat.

Clinical Signs

Blackhead disease can cause a range of clinical signs in affected birds, including depression, lethargy, decreased appetite, weight loss, diarrhea, and yellow discoloration of the skin and comb. Infected birds may also exhibit respiratory distress, reduced egg production, and increased mortality rates.

In advanced cases, birds may develop liver necrosis, which can be fatal. However, some birds may carry the parasite without exhibiting any symptoms, making it difficult to identify and control the disease.


Diagnosing blackhead disease can be challenging, as the clinical signs can be similar to other diseases, and some birds may not exhibit any symptoms. However, several laboratory tests can help identify the disease, including histopathology, serology, and PCR tests.


Unfortunately, there is no specific treatment for blackhead disease. However, it is possible to control the disease through management practices and preventive measures.

One of the most effective management practices is to limit the presence of earthworms in the environment. This can be done by reducing the number of wild turkeys or other game birds that are present in the area, as these birds can act as carriers for the disease. It is also important to avoid overstocking or overcrowding of birds, as this can increase the likelihood of transmission.

In addition, there are a few preventative measures that can be taken to reduce the risk of infection. One of the most effective measures is to feed birds a diet that is low in protein, which can reduce the number of cecal worms that are present in the digestive tract. Another preventative measure is to use a medicated feed that contains drugs such as nitroimidazole or histomonacides, which can help to control the growth of cecal worms and reduce the severity of the disease.

It is important to note that the use of antibiotics to treat blackhead disease is not recommended, as these drugs are ineffective against the protozoan parasite that causes the disease. In addition, the use of antibiotics can promote the growth of antibiotic-resistant bacteria, which can have serious consequences for both human and animal health.

Overall, the best approach to managing blackhead disease is to focus on preventative measures and good management practices. By reducing the presence of earthworms, controlling the population of wild birds, and providing a low-protein diet and medicated feed, it is possible to reduce the risk of infection and control the spread of the disease.


Prevention of blackhead disease is critical for the conservation of affected species. As there are currently no vaccines available, management strategies focus on reducing the risk of infection.

  1. Habitat management: Proper habitat management practices such as rotating grazing lands, avoiding overstocking of domestic birds, and preventing contact between wild and domestic birds can reduce the spread of the disease.
  2. Biosecurity measures: It is essential to practice good biosecurity measures to reduce the spread of blackhead disease. This can include isolating new birds, restricting access to visitors, disinfecting equipment and footwear, and controlling rodents.
  3. Treatment: Treatment of blackhead disease can be challenging, and prevention is the best approach. If an infected bird is identified, it should be removed from the population to prevent the spread of the disease. Sick birds should be treated immediately with antibiotics, supportive care, and anti-inflammatory medication to reduce the severity of the infection.
  4. Monitoring: Regular monitoring of bird populations can help to identify the presence of blackhead disease and its prevalence. Monitoring can also help in identifying potential sources of infection and implementing management strategies.
  5. Research: Research is necessary to develop new strategies for managing blackhead disease in wildlife. Research should focus on the development of vaccines, effective treatment, and better understanding of the transmission dynamics of the disease.

Overall, prevention of blackhead disease in wildlife populations is crucial for the conservation of affected species. The implementation of effective management strategies, including habitat management, biosecurity measures, treatment of infected birds, monitoring, and research, can help reduce the risk of infection and prevent the spread of the disease.


Blackhead disease is a highly infectious and fatal disease that affects various species of birds, including wild and domestic turkeys, chickens, pheasants, quail, and guinea fowl. The disease is caused by the protozoan parasite Histomonas meleagridis, which can infect birds through the ingestion of infected worms or cecal droppings from infected birds. Clinical signs include depression, lethargy, diarrhea, and weight loss. A definitive diagnosis of the disease is made through the identification of the parasite in cecal droppings or tissues.

Currently, no effective treatment for blackhead disease exists, and prevention is the key to controlling the disease. Preventive measures include avoiding the use of shared water sources between infected and uninfected birds, minimizing the introduction of earthworms to bird pens, and maintaining strict biosecurity measures. Additionally, vaccines are available for use in turkeys to prevent the disease.

Blackhead disease remains a significant threat to the poultry industry, and its impact on wild bird populations is still being studied. It is essential for poultry farmers, wildlife biologists, and zoologists to understand the disease’s causes, clinical signs, and prevention strategies to minimize its impact on bird populations.

Further research on the disease’s epidemiology, pathogenesis, and immunity is necessary to develop more effective control and prevention measures. By implementing a holistic approach to the management of blackhead disease, the disease’s impact on bird populations can be minimized, leading to healthier and more resilient bird populations.


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