Centre for Biomolecular Interactions Bremen, Department of Biology and Chemistry, University of Bremen, Bremen, Germany.
Department of Biology, Faculty of Exacts and Applied sciences, University of N'Djamena, N'Djamena, Chad.
PLoS Negl Trop Dis. 2021 Jun 9;15(6):e0009323. doi: 10.1371/journal.pntd.0009323. eCollection 2021 Jun.
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.
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.
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.
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.
非洲锥体虫主要通过采采蝇传播，是一种寄生在人体（人类锥体虫病，HAT）和动物（动物锥体虫病，AAT）中的寄生虫。乍得存在 HAT/AAT 的地方流行。本研究调查了曼杜尔（一个正在进行采采蝇控制运动的孤立地区）和马罗（与中非共和国接壤的地区，尚未开始控制）的锥体虫的多样性和分布。
采集了 717 个人类和 540 份牛血样，并捕获了 177 只采采蝇。使用针对内部转录间隔区 1（ITS1）和糖酵解甘油醛-3 磷酸脱氢酶（gGAPDH）的 PCR 检测锥虫 DNA，随后进行扩增子测序。
在 14 个人类样本、227 份牛样本和采采蝇中检测到锥虫 DNA。除 T. b. gambiense 外，还在马罗的人类中检测到 T. congolense。在曼杜尔，在一名曾患有已治愈的 HAT 感染但持续存在症状的人类中，检测到了一种未知的 Trypanosoma sp.-129-H 的 DNA。在马罗的牛和采采蝇样本中，除了已知的动物病原体外，还检测到了 T. godfreyi 和 T. grayi，此外，在牛中还检测到了 T. theileri（在采采蝇中）和 T. simiae（在采采蝇中）。此外，在马罗的采采蝇中还获得了其他未知锥体虫的证据。相比之下，在曼杜尔地区，仅在牛中检测到 T. theileri、T. simiae 和 T. vivax 的 DNA。T. vivax 和 T. theileri 的遗传多样性最为显著。
曼杜尔的采采蝇控制活动减少了采采蝇的数量，从而减少了致病寄生虫的数量。然而，T. theileri、T. vivax 和 T. simiae 在牛中很常见，这表明它们可能通过其他昆虫媒介传播。相比之下，在马罗，与中非共和国的季节性迁徙和没有采采蝇控制可能导致观察到的高度多样性和频率的锥体虫，包括 HAT/AAT 致病物种。活跃的 HAT 感染强调了加强监测和控制活动的必要性。此外，人类和牛中不同的锥体虫种类表明有必要调查未知锥体虫的感染性，以评估其人畜共患潜力。最后，这项研究应该扩大到其他锥体虫宿主，以捕获循环锥体虫的全部多样性。
