A comprehensive approach to diagnose and prevent Blackhead disease
Barrios, Miguel Alejandro
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Histomonas meleagridis, a protozoan parasite, is the causative agent of Blackhead disease. Heterakis gallinarum, also known as a cecal worm, commonly infects different poultry species. These two parasites, H. meleagridis and H. gallinarum have developed a symbiotic relationship. H. meleagridis is anaerobic and it inhabits in the cecal worm and its eggs, which allows H. meleagridis to survive in the environment. H. gallinarum eggs can remain infective in the soil for years, meaning that Blackhead disease remains in the environment. Blackhead disease may cause up to 100% and 30% mortality in turkeys and chickens, respectively. Blackhead disease negatively impacts flock uniformity and egg production in broiler breeder flocks as well. A molecular diagnostic strategy using PCR for Blackhead disease was developed by designing primers for H. gallinarum. This test allows producers to identify disease reservoirs in order to mitigate Blackhead disease outbreaks. The PCR strategy also allows investigators to understand the epidemiology of the disease by analyzing different types of samples in the environment. For better collaboration between producers and investigators, a dry culture medium was developed that permits long-term storage of the media needed in the field. Dry H. meleagridis medium allows for rapid, onsite preparation of culture media that will allow field veterinarians and staff at farms infected with Blackhead disease to collect field strains of H. meleagridis. Research of these field strains may then aid in understanding the virulence and treatment of H. meleagridis. Using these strains, chemicals, heavy metals and their combination were tested in an in vitro H. meleagridis cell screen, as well as, a direct and lateral Blackhead disease model. One treatment, 3-nitrophenylboronic acid showed promise as a possible treatment. Inclusion of heavy metals did not ameliorate the effects of Blackhead disease. Further work is necessary to test other generally recognized as safe compounds that may be immediately used to prevent or cure Blackhead disease.