Morphological and molecular characterization of avian trypanosomes in domestic chickens (Gallus gallus domesticus) in Southeast Asia and review of the parasite morphometry in different avian hosts

Avian trypanosomiasis is caused by flagellate protists of the genus Trypanosoma (Trypanosomatidae, Kinetoplastida). These parasites are transmitted by various blood-sucking arthropods. While these parasites are generally considered to have low pathogenicity, certain species can induce clinical symptoms in susceptible birds. In this study, detailed morphological and molecular characteristics of Trypanosoma species isolated from domestic chickens (Gallus gallus domesticus) in Northeastern Thailand were investigated. In total, 58 buffy coat blood films, 60 thin blood films of fresh blood and 60 partial DNA sequences were analyzed. Subsequently, Trypanosoma avium and Trypanosoma calmettei, which are rarely reported species in poultry and Trypanosoma sp. were characterized. Additionally, we provided the details of reviewed information of the parasite morphometry in different avian hosts. Phylogenetic analysis identified the most closely related avian Trypanosoma lineages. This study reports T. avium in domestic chickens, along with the molecular characterization of T. calmettei, which are rarely reported species. Buffy coat and nested-PCR diagnostic methods were similar in terms of sensitivity for trypanosome diagnostics, and both methods were more sensitive than microscopic examination of thin blood films. The relatively cheap buffy coat method is helpful for screening trypanosome infection in poultry, particularly during rapid fieldwork. In parasitology research, buffy coat and nested-PCR diagnostics are worth combining with thin blood smear microscopic examination, which provides valuable information about non-deformed trypomastigotes that is essential for morphospecies identification.

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