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News Article

Histomonosis: a re-emerging poultry disease

Withdrawal of drugs used for prophylactic and therapeutic purposes has resulted in the re-emergence of histomonosis (blackhead disease) in turkeys and chickens

Due to a ban of efficacious drugs for prophylaxis and therapeutic purposes, histomonosis – also known as blackhead disease – is on the rise in poultry. The disease, caused by the protozoan parasite Histomonas meleagridis, affects turkeys, chickens and certain game birds. The progression of the disease is often particular severe among turkeys. Researchers from the University of Veterinary Medicine, Vienna (Vetmeduni Vienna) discuss the re-emergence of the disease in a spotlight published in Avian Pathology.

A special feature of the parasite is its intricate interaction with bacteria, both in vitro and in vivo. This important influencing factor has been studied by Michael Hess, head of the University Clinic for Poultry and Fish Medicine at Vetmeduni Vienna, and his colleagues Based on their analyses, the parasite-bacteria interaction could represent a symbiosis with fatal consequences for the host. However, the underlying functional mechanisms need to be resolved in future studies. An article on the interplay between H. meleagridis and bacteria is published in Trends in Parasitology.

New prophylactic and therapeutic interventions are required for histomonosis. An experimental vaccine developed at the Christian Doppler Laboratory for Innovative Poultry Vaccines (IPOV) at Vetmeduni Vienna has been shown to provide protection. However, the researchers say several technical questions still need to be answered before the vaccine is ready for use in the field. The interaction between H. meleagridis and intestinal bacteria is of fundamental importance for the success of vaccination.

“Future research should focus on resolving the unknowns of the interaction between bacteria and H. meleagridis, especially to elaborate whether a targeted manipulation of the gut microbiome could minimize clinical consequences. Similarly, such knowledge could also be used to optimize the newly developed vaccination strategy. More detailed investigations should also help to explain the huge variations in mortality and the manifestation of the parasite on certain farms,” says Michael Hess.

The researchers say that special attention should also be paid to the nematode Heterakis gallinarum. The infection it causes is only mildly pathogenic but, as a common carrier of H. meleagridis, it is the most important vector for the transmission of the protozoan parasite. H. meleagridis survives up to three years in the nematode’s eggs.

More research on H. meleagridis and blackhead disease is needed, the researchers note in the Avian Pathology article. “The complicated nature of the pathogen, its epidemiology and the various influences on the pathogenesis of the disease need substantial efforts in order to develop a sophisticated protection strategy.”


Liebhart, D., Hess, M. (2020). Spotlight on Histomonosis (blackhead disease): a re-emerging disease in turkeys and chickens. Avian Pathology 49(1):1-4, doi: 10.1080/03079457.2019.1654087

Bilic, I., Hess, M. (2020). Interplay between Histomonas meleagridis and Bacteria: Mutualistic or Predator-Prey? Trends in Parasitology, online 22 January 2020, doi: 10.1016/

Article details

  • Date
  • 06 February 2020
  • Source
  • Vetmeduni Vienna
  • Subject(s)
  • Poultry