Diversity of trypanosomes in humans and cattle in the HAT foci Mandoul and Maro, Southern Chad—A matter of concern for zoonotic potential?

Abstract

Background African trypanosomes are parasites mainly transmitted by tsetse flies. They cause trypanosomiasis in humans (HAT) and animals (AAT). In Chad, HAT/AAT are endemic. This study investigates the diversity and distribution of trypanosomes in Mandoul, an isolated area where a tsetse control campaign is ongoing, and Maro, an area bordering the Central African Republic (CAR) where the control had not started. Methods 717 human and 540 cattle blood samples were collected, and 177 tsetse flies were caught. Trypanosomal DNA was detected using PCR targeting internal transcribed spacer 1 (ITS1) and glycosomal glyceraldehyde-3 phosphate dehydrogenase (gGAPDH), followed by amplicon sequencing. Results Trypanosomal DNA was identified in 14 human samples, 227 cattle samples, and in tsetse. Besides T. b. gambiense, T. congolense was detected in human in Maro. In Mandoul, DNA from an unknown Trypanosoma sp.-129-H was detected in a human with a history of a cured HAT infection and persisting symptoms. In cattle and tsetse samples from Maro, T. godfreyi and T. grayi were detected besides the known animal pathogens, in addition to T. theileri (in cattle) and T. simiae (in tsetse). Furthermore, in Maro, evidence for additional unknown trypanosomes was obtained in tsetse. In contrast, in the Mandoul area, only T. theileri, T. simiae, and T. vivax DNA was identified in cattle. Genetic diversity was most prominent in T. vivax and T. theileri. Conclusion Tsetse control activities in Mandoul reduced the tsetse population and thus the pathogenic parasites. Nevertheless, T. theileri, T. vivax, and T. simiae are frequent in cattle suggesting transmission by other insect vectors. In contrast, in Maro, transhumance to/from Central African Republic and no tsetse control may have led to the high diversity and frequency of trypanosomes observed including HAT/AAT pathogenic species. Active HAT infections stress the need to enforce monitoring and control campaigns. Additionally, the diverse trypanosome species in humans and cattle indicate the necessity to investigate the infectivity of the unknown trypanosomes regarding their zoonotic potential. Finally, this study should be widened to other trypanosome hosts to capture the whole diversity of circulating trypanosomes.

A review on the diagnosis of animal trypanosomoses

“…Diagnostic methods for detecting T. lewisi in rats are thus needed for risk analysis and, conversely, diagnosis of this species may also be required in humans. Several human infections by T. congolense were recently exposed by PCR examination in a survey in Maro, southern Chad [ 78 ], suggesting that human infections with T. congolense might be more frequent than previously thought. In any case, these surprising results certainly need confirmation.…”

Atypical human trypanosomosis: Potentially emerging disease with lack of understanding

“…• The existing paradox in medical science after the finding on intact functional apolipoprotein L1 (ApoL1) in Vietnam T. evansi Type A case is also discussed. (Ibrahim et al, 2021). The human cases of infection from animal trypanosomes are mostly determined in Asia and Africa (Van Vinh Chau et al, 2016).…”

“…In 2021, T. congolense was molecular confirmed in 11 humans of Maro (Southern Chad) region of Africa. They also reported an unidentified Trypanosoma sp‐125‐H recorded from a human in Mandoul region of Chad, which phylogenetically cluster with hyaena isolate (Ibrahim et al., 2021). The human cases of infection from animal trypanosomes are mostly determined in Asia and Africa (Van Vinh Chau et al., 2016).…”

Vector competence of sterile male Glossina fuscipes fuscipes for Trypanosoma brucei brucei: implications for the implementation of the sterile insect technique in a sleeping sickness focus in Chad

“…The Mandoul focus, located in the Logone Oriental part of Southern Chad, is a historical g-HAT focus [ 2 ] showing the highest transmission rate in the country in the last decades. It is an agro-pastoral area covering > 520 km 2 with fertile land because of the proximity of a river, where there are many cattle, sheep, goats and pigs [ 2 ] and where African animal trypanosomosis (AAT) is also present [ 3 , 4 ]. Glossina fuscipes fuscipes was found as the only cyclical vector of trypanosomes in this area [ 3 ], with an apparent density of 0 to 26 tsetse flies per trap per day at the end of 2013 [ 5 ].…”