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African animal trypanosomosis (nagana) is becoming prevalent beyond its traditionally defined geographical boundaries in African tsetse belts. However, knowledge of clinically important trypanosomes and infection rate in non-tsetse hematophagous flies and domestic animals are limited. This study characterized the potential mechanical vectors, their host feeding patterns, and trypanosome infection in them and domestic animals outside the tsetse belt in northern Kenya. Field-trapped flies and blood from camels, cattle, donkeys, goats, and sheep were screened for trypanosome infection by microscopy and polymerase chain reaction (PCR) of the internal transcribed spacer 1 region. Blood-fed specimens were analysed using PCR-HRM and/or sequencing of 16S rRNA gene to identify vertebrate blood-meal host sources. Hippobosca camelina, Stomoxys calcitrans, Tabanus spp., and Pangonia rueppellii were identified as potential vectors of trypanosomes outside the tsetse belt in Marsabit County. The trypanosome species, Trypanosoma vivax, T. evansi, T. brucei, and T. congolense were recovered in biting flies as well as in camels (Camelus dromedarius). The diversity of parasites in the biting flies was similar to that detected in the tsetse fly Glossina pallidipes collected from the tsetse-infested Shimba Hills, in coastal Kenya, suggesting a wide geographic distribution of the trypanosomes in Kenya. The biting flies fed on camels, cattle, goats, and sheep. Furthermore, we identified diverse clinical outcomes based on PCV (anemia), heamorrhagia) associated with infection with disparate Trypanosoma species. Thus, infection of flies and camels by diverse Trypanosoma species could contribute to the complex epidemiology of observed trypanosomosis in camels. [ABSTRACT FROM AUTHOR]

Insects that transmit many of the world's deadliest animal diseases, for instance trypanosomosis, find their suitable hosts and avoid non-preferred hosts mostly through olfactory cues. The waterbuck repellent blend (WRB) comprising geranylacetone, guaiacol, pentanoic acid, and δ-octalactone derived from waterbuck skin odor is a repellent to some savannah-adapted tsetse flies and reduces trap catches of riverine species. However, the cellular and molecular mechanisms associated with detection and coding of the repellent odors remain to be elucidated. Here, we demonstrated that WRB inhibited blood feeding in both Glossina pallidipes Austen, 1903 and Glossina fuscipes fuscipes Newstead, 1910. Using the DREAM (D eorphanization of R eceptors based on E xpression A lterations in odorant receptor m RNA levels) technique, combined with ortholog comparison and molecular docking, we predicted the putative odorant receptors (ORs) for the WRB in G. f. fuscipes , a non-model insect. We show that exposure of G. f. fuscipes in vivo to WRB odorant resulted in up- and downregulation of mRNA transcript of several ORs. The WRB component with strong feeding inhibition altered mRNA transcript differently as compared to an attractant odor, showing these two odors of opposing valence already segregate at the cellular and molecular levels. Furthermore, molecular dynamics simulations demonstrated that the predicted ligand–OR binding pockets consisted mostly of hydrophobic residues with a few hydrogen bonds but a stable interaction. Finally, our electrophysiological response showed the olfactory sensory neurons of G. f. fuscipes tuned to the tsetse repellent components in different sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

Olfaction is orchestrated at different stages and involves various proteins at each step. For example, odorant-binding proteins (OBPs) are soluble proteins found in sensillum lymph that might encounter odorants before reaching the odorant receptors. In tsetse flies, the function of OBPs in olfaction is less understood. Here, we investigated the role of OBPs in Glossina fuscipes fuscipes olfaction, the main vector of sleeping sickness, using multidisciplinary approaches. Our tissue expression study demonstrated that GffLush was conserved in legs and antenna in both sexes, whereas GffObp44 and GffObp69 were expressed in the legs but absent in the antenna. GffObp99 was absent in the female antenna but expressed in the male antenna. Short odorant exposure induced a fast alteration in the transcription of OBP genes. Furthermore, we successfully silenced a specific OBP expressed in the antenna via dsRNAi feeding to decipher its function. We found that silencing OBPs that interact with 1-octen-3-ol significantly abolished flies' attraction to 1-octen-3-ol, a known attractant for tsetse fly. However, OBPs that demonstrated a weak interaction with 1-octen-3-ol did not affect the behavioral response, even though it was successfully silenced. Thus, OBPs' selective interaction with ligands, their expression in the antenna and their significant impact on behavior when silenced demonstrated their direct involvement in olfaction. [ABSTRACT FROM AUTHOR]