Trichomonad Disease in Wild Turkeys (Meleagris gallopavo): Pathology and Molecular Characterization of Histomonas, Tetratrichomonas, Tritrichomonas, and Simplicimonas spp.

Abstract

The Wild Turkey (Meleagris gallopavo) is a geographically widespread, popular game bird and conservation icon in North America. Following successful reestablishment in parts of the US and Canada, regional declines have fueled population health concerns; therefore, understanding mortality causes and spatiotemporal patterns of disease is important to uncover potential ongoing and future health risks. Histomonosis, caused by the trichomonad Histomonas meleagridis, is a well-established and potentially fatal disease in Wild Turkeys; however, its prevalence and potential population health impacts remain poorly understood. Moreover, molecular tools recently have allowed for the detection of additional trichomonads that similarly can cause fatal disease in Wild Turkeys. We describe and compare disease due to H. meleagridis with that of Tetratrichomonas gallinarum, Tritrichomonas sp., and Simplicimonas sp. in Wild Turkeys in the southeastern US. Among 857 Wild Turkeys evaluated postmortem from 2002 to 2023, 34 (4.0%) were diagnosed with trichomonad disease, often assumed to be histomonosis prior to molecular testing. However, among 25 debilitating to fatal trichomonad disease cases for which etiologies were confirmed by PCR from 2015 to 2023, H. meleagridis was detected in 16/25 (64.0%), T. gallinarum in 6/25 (24.0%), Tritrichomonas sp. in 2/25 (8.0%) and Simplicimonas sp. in 1/25 (4.0%). These turkeys had similar clinical manifestations, and although lesion patterns varied to some extent, liver and/or intestinal tract was most commonly affected. Coinfections were common among all turkeys with trichomonad disease from 2015 to 2023 (21/25, 84.0%) and included viruses (lymphoproliferative disease virus, avian poxvirus), bacteria (Streptococcus gallolyticus, Listeria monocytogenes, Escherichia coli), and other protozoa (Sarcocystis sp., Haemoproteus sp.). Our results highlight the importance of molecular diagnostic testing in determining etiologies of trichomonad disease in Wild Turkeys. Further evaluation of the epidemiology and pathogenesis of trichomonad disease and its varied etiologies in Wild Turkeys and other birds is warranted to better understand risk factors and potential health impacts.