Feed Composition and Isolate of Histomonas meleagridis Alter Horizontal Transmission of Histomonosis in Turkeys. Proof of Concept

Metabolic Profile of Histomonas meleagridis in Dwyer's Media with and Without Rice Starch

BACKGROUND AND OBJECTIVES

Histomonas meleagridis, the causative agent of histomonosis (i.e., blackhead disease), threatens the poultry industry with serious economic losses due to its high mortality and morbidity in turkey and chicken flocks. In vitro studies are complicated by the inability to culture the parasite axenically. Histomonas meleagridis has been propagated in Dwyer's media, which contains a starch source and serum, for over 50 years. The presence of insoluble starch component in Dwyer's media represents an obstacle for the commercialization of such media, and the role of starch in media is poorly understood.

METHODS

To investigate the intracellular metabolomic differences in H. meleagridis and undefined bacteria grown in Dwyer's media with rice starch (SD) and without rice starch (NR), we conducted a global metabolomics analysis using ultra-high-performance liquid chromatography-high-resolution mass spectrometry.

RESULTS

SD significantly supported the growth of H. meleagridis compared to NR. There was no significant difference in bacterial growth between SD and NR media at various timepoints. From the intracellular metabolic analysis of samples collected from the SD and NR media, a total of 170 known metabolites were identified. H. meleagridis appears to be the major contributor to global metabolic differences.

CONCLUSIONS

We found that riboflavin had the highest variable importance in the projection score, and metabolites involved in riboflavin biosynthesis significantly contributed to the differences between SD and NR in the media immediately after the inoculation of H. meleagridis and undefined bacteria, warranting further investigations into the role of riboflavin biosynthesis in H. meleagridis growth.

Concurrent Histomonas meleagridis and Hemorrhagic Enteritis Virus Infection in a Turkey Flock with Recurrent History of Blackhead Disease

Intestinal health is one of the key factors required for the growth and production of turkeys. Histomoniasis (blackhead disease), caused by a protozoan parasite, Histomonas meleagridis, is a reemerging threat to the turkey industry. Increased incidences of histomoniasis have been reported in recent years due to withdrawal of antihistomonas treatments. H. meleagridis affects ceca and causes cecal inflammation and necrosis. H. meleagridis migrates from ceca to the liver and causes liver necrosis, resulting in high mortalities. Ironically, field outbreaks of histomoniasis are not always associated with high mortalities, while low mortalities have also been documented. There are several exacerbating factors associated with high mortality rates in histomoniasis outbreaks, with concurrent infection being one of them. Recurrent histomoniasis outbreaks in a newly constructed barn were documented, and concurrent infection of H. meleagridis and hemorrhagic enteritis virus was confirmed. Currently, neither commercial vaccines nor prophylactic or therapeutic solutions are available to combat histomoniasis. However, there are treatments, vaccines, and solutions to minimize or prevent concurrent infections in turkeys. In addition to implementing biosecurity measures, measures to prevent concurrent infections are critical steps that the turkey industry can follow to reduce mortality rates and minimize the production and economic losses associated with histomoniasis outbreaks.