A collaborative research effort to combat histomonosis, a deadly disease affecting turkey populations, has received a significant boost with a $3.2 million grant from the U.S. Food and Drug Administration (FDA). The funding will support a five-year study led by Danielle Graham, an assistant professor of poultry science at the University of Arkansas System Division of Agriculture, and Zhicheng Dou, an associate professor at Clemson University, focusing on the transmission mechanisms of Histomonas meleagridis, the parasite responsible for the disease.
Understanding Histomonosis and its Impact
Histomonosis, also known as blackhead disease, poses a significant threat to turkey farming, with mortality rates in infected flocks reaching as high as 80%. Chickens are also susceptible, though typically experience lower mortality. Currently, there are no FDA-approved vaccines or therapeutics available to effectively treat the disease, making it a major concern for commercial turkey producers, particularly in the lower Midwest and Southeast United States.
Arkansas ranks third nationally in turkey production, accounting for $614 million in cash farm receipts in 2022. The grant underscores the importance of addressing this critical issue for the state's agricultural economy.
Challenging Traditional Transmission Theories
For over half a century, the prevailing theory has been that histomonosis primarily spreads through vectors like the nematode Heterakis gallinarium or earthworms acting as paratenic hosts. However, recent preliminary studies by Graham and Dou suggest that H. meleagridis can survive the acidic environment of the turkey's digestive tract and form cyst-like structures, potentially enabling direct fecal-oral transmission.
"Over the last 50-plus years, the thought was that histomonosis could only be efficiently transmitted outside of a host by a vector... But in turkeys, that nematode doesn't reproduce efficiently. So, it doesn't make sense for it to be the primary way for these protozoa to transmit in a turkey flock," Graham explained.
The research will investigate whether cloacal contact with infected feces or direct cloacal-to-cloacal contact is sufficient for rapid transmission in the absence of a vector. Given that avian species commonly consume fecal matter, the team's preliminary findings suggest a significant potential for fecal-oral transmission, with the cyst-like formation protecting the parasites during their journey through the digestive system.
Implications for Disease Control
By elucidating the transmission pathways of H. meleagridis, the study aims to identify potential targets for intervention. Developing inhibitors against the cyst formation stage, for example, could prove pivotal in controlling infections. Furthermore, the researchers will explore the possibility of repurposing existing FDA-approved drugs to combat histomonosis.
The FDA's support through the Animal and Veterinary Innovation Center highlights the urgency of addressing this animal health challenge. The outcomes of this research are expected to contribute significantly to the development of effective strategies for preventing and managing histomonosis in turkey populations, thereby mitigating economic losses and improving animal welfare.
