Researcher Looks For Alternative Control Methods For Blackhead In Turkeys

 

Blackhead Disease (Histomoniasis): Test the Ability of Zinc to Treat Blackhead Disease and Improve the Efficacy of Nitarsone

 

Without the highly effective nitroimidazole products to treat Blackhead outbreaks, the industry has used the arsenical Nitarsone (Histostat 50). Nitarsone is not effective as a treatment, but acts as a preventive when used in the feed during outbreaks.

 

Unfortunately, as of Jan. 1, Nitarsone is not legal for use in feeds in the USA. The lack of efficacious preventatives and treatments against Blackhead creates a deep void in both turkey and chicken production, which must be resolved. Research in this grant focused on identifying compounds that inhibit Histomonas meleagridis (the causative agent of Blackhead) growth in cell screen assays, followed by testing thes compounds in disease models in turkeys. Because of the loss of Nitarsone, we also tested 3-nitrophenylboronic acid and 4-nitrophenylboronic acid, similar structural compounds to Nitarsone, for their ability to inhibit Blackhead.

 

 

Chemicals such as 3-nitrophenylboronic acid, 4-nitrophenylboronic acid and heavy metals (copper, zinc, manganese, iron, cadmium, and nickel) were tested at different concentrations alone and in combination in culture. Our screen showed that copper, zinc, cadmium, manganese and nickel alone were effective in inhibiting growth of H. meleagridis cells. 3-nitrophenylboronic acid and 4-nitrophenylboronic acid showed some ability to inhibit and kill H. meleagridis cells, which led to research to test a synergistic effect of these two chemical compounds with metal ions. Nickel, zinc and copper with 3-nitrophenylboronic acid inhibited growth of H. meleagridis cells. Copper and zinc with 4-nitrophenylboronic acid inhibited the growth of H. meleagridis cells.

 

Disease models were used to extrapolate these in vitro results in turkeys. Zinc and copper did not treat or inhibit the transmission of Blackhead disease. In the direct infection trial, the inclusion of 3-nitrophenylboronic acid reduced average cecal and liver lesions and mortality was reduced by approximately 40 percent. The inclusion of heavy metals with 3-nitrophenylboronic acid did not improve lesions or overall mortality. These compounds were also tested in a lateral infection model and results showed that the inclusion of 3-nitrophenylboronic acid with and without copper and zinc did not improve lesions or overall mortality as compared to the infected control. Additionally, while zinc and copper potentiated the effect of Nitarsone in cultures, they inhibited its ability to prevent disease in the turkey. These studies highlight the difficulty in taking bench top research and applying it to an industrial model.