International Centre of Insect Physiology and Ecology (icipe), Nairobi, Kenya.
Biochemistry and Molecular Biology Department, Egerton University, Nakuru, Kenya.
PLoS Negl Trop Dis. 2021 Jan 6;15(1):e0008267. doi: 10.1371/journal.pntd.0008267. eCollection 2021 Jan.
African trypanosomiasis (AT) is a neglected disease of both humans and animals caused by Trypanosoma parasites, which are transmitted by obligate hematophagous tsetse flies (Glossina spp.). Knowledge on tsetse fly vertebrate hosts and the influence of tsetse endosymbionts on trypanosome presence, especially in wildlife-human-livestock interfaces, is limited. We identified tsetse species, their blood-meal sources, and correlations between endosymbionts and trypanosome presence in tsetse flies from the trypanosome-endemic Maasai Mara National Reserve (MMNR) in Kenya. Among 1167 tsetse flies (1136 Glossina pallidipes, 31 Glossina swynnertoni) collected from 10 sampling sites, 28 (2.4%) were positive by PCR for trypanosome DNA, most (17/28) being of Trypanosoma vivax species. Blood-meal analyses based on high-resolution melting analysis of vertebrate cytochrome c oxidase 1 and cytochrome b gene PCR products (n = 354) identified humans as the most common vertebrate host (37%), followed by hippopotamus (29.1%), African buffalo (26.3%), elephant (3.39%), and giraffe (0.84%). Flies positive for trypanosome DNA had fed on hippopotamus and buffalo. Tsetse flies were more likely to be positive for trypanosomes if they had the Sodalis glossinidius endosymbiont (P = 0.0002). These findings point to complex interactions of tsetse flies with trypanosomes, endosymbionts, and diverse vertebrate hosts in wildlife ecosystems such as in the MMNR, which should be considered in control programs. These interactions may contribute to the maintenance of tsetse populations and/or persistent circulation of African trypanosomes. Although the African buffalo is a key reservoir of AT, the higher proportion of hippopotamus blood-meals in flies with trypanosome DNA indicates that other wildlife species may be important in AT transmission. No trypanosomes associated with human disease were identified, but the high proportion of human blood-meals identified are indicative of human African trypanosomiasis risk. Our results add to existing data suggesting that Sodalis endosymbionts are associated with increased trypanosome presence in tsetse flies.
非洲锥虫病（AT）是一种由锥虫寄生虫引起的人类和动物的被忽视疾病，这些寄生虫通过专性吸血的采采蝇（ Glossina spp.）传播。关于采采蝇的脊椎动物宿主以及采采蝇内共生菌对锥虫存在的影响，特别是在野生动物-人类-牲畜界面，知之甚少。我们在肯尼亚锥虫病流行的马赛马拉国家保护区（MMNR）中鉴定了采采蝇的种类、它们的血液来源，以及内共生菌与采采蝇中锥虫存在之间的相关性。从 10 个采样点采集的 1167 只采采蝇（1136 只苍白采采蝇，31 只斯氏采采蝇）中，28 只（2.4%）通过 PCR 对锥虫 DNA 呈阳性，其中大多数（17/28）为锥虫 vivax 种。基于对脊椎动物细胞色素 c 氧化酶 1 和细胞色素 b 基因 PCR 产物的高分辨率熔解分析的血液分析（n = 354），确定人类是最常见的脊椎动物宿主（37%），其次是河马（29.1%）、非洲野牛（26.3%）、大象（3.39%）和长颈鹿（0.84%）。携带锥虫 DNA 的苍蝇更有可能吸食河马和水牛的血液。如果采采蝇携带 Sodalis glossinidius 共生菌，它们更有可能携带锥虫（P = 0.0002）。这些发现表明，在马赛马拉国家保护区等野生动物生态系统中，采采蝇与锥虫、内共生菌和多种脊椎动物宿主之间存在着复杂的相互作用，这在控制计划中应予以考虑。这些相互作用可能有助于采采蝇种群的维持和/或非洲锥虫的持续循环。虽然非洲野牛是 AT 的一个关键储存宿主，但在携带锥虫 DNA 的苍蝇中，河马血液的比例更高，表明其他野生动物物种可能在 AT 传播中很重要。没有发现与人类疾病相关的锥虫，但鉴定出的人类血液比例很高，表明存在人类非洲锥虫病的风险。我们的结果增加了现有的数据，表明 Sodalis 共生菌与采采蝇中锥虫的存在增加有关。
