Spatio-temporal distribution of Spiroplasma infections in the tsetse fly (Glossina fuscipes fuscipes) in northern Uganda
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Date
2019
Journal Title
Journal ISSN
Volume Title
Publisher
PLOS Neglected Tropical Diseases
Abstract
Tsetse flies (Glossina spp.) are vectors of parasitic trypanosomes, which cause human
(HAT) and animal African trypanosomiasis (AAT) in sub-Saharan Africa. In Uganda, Glossina
fuscipes fuscipes (Gff) is the main vector of HAT, where it transmits Gambiense disease
in the northwest and Rhodesiense disease in central, southeast and western regions.
Endosymbionts can influence transmission efficiency of parasites through their insect vectors
via conferring a protective effect against the parasite. It is known that the bacterium
Spiroplasma is capable of protecting its Drosophila host from infection with a parasitic nematode.
This endosymbiont can also impact its host’s population structure via altering host
reproductive traits. Here, we used field collections across 26 different Gff sampling sites in
northern and western Uganda to investigate the association of Spiroplasma with geographic
origin, seasonal conditions, Gff genetic background and sex, and trypanosome infection status.
We also investigated the influence of Spiroplasma on Gff vector competence to trypanosome
infections under laboratory conditions. Generalized linear models (GLM) showed that
Spiroplasma probability was correlated with the geographic origin of Gff host and with the
season of collection, with higher prevalence found in flies within the Albert Nile (0.42 vs
0.16) and Achwa River (0.36 vs 0.08) watersheds and with higher prevalence detected in
flies collected in the intermediate than wet season. In contrast, there was no significant correlation
of Spiroplasma prevalence with Gff host genetic background or sex once geographic
origin was accounted for in generalized linear models. Additionally, we found a
potential negative correlation of Spiroplasma with trypanosome infection, with only 2% of
Spiroplasma infected flies harboring trypanosome co-infections. We also found that in a laboratory
line of Gff, parasitic trypanosomes are less likely to colonize the midgut in individuals
that harbor Spiroplasma infection. These results indicate that Spiroplasma infections in tsetse may be maintained by not only maternal but also via horizontal transmission routes,
and Spiroplasma infections may also have important effects on trypanosome transmission
efficiency of the host tsetse. Potential functional effects of Spiroplasma infection in Gff could
have impacts on vector control approaches to reduce trypanosome infections.
Description
Keywords
Spatio-temporal distribution, Spiroplasma infections, Tsetse fly (Glossina fuscipes fuscipes), Northern Uganda
Citation
Schneider DI, Saarman N, Onyango MG, Hyseni C, Opiro R, Echodu R, et al. (2019) Spatiotemporal distribution of Spiroplasma infections in the tsetse fly (Glossina fuscipes fuscipes) in northern Uganda. PLoS Negl Trop Dis 13(8): e0007340. https://doi.org/10.1371/journal. pntd.0007340