Opiro Robert, Opoke Robert, Angwech Harriet, Nakafu Esther, Oloya Francis A, Openy Geoffrey, Njahira Moses, Macharia Mercy, Echodu Richard, Malinga Geoffrey M, Opiyo Elizabeth A
Department of Biology, Faculty of Science, Gulu University, P.O Box 166, Gulu, Uganda.
Department of Biology, Faculty of Science, Muni University, P.O Box 725, Arua, Uganda.
BMC Vet Res. 2021 Nov 29;17(1):365. doi: 10.1186/s12917-021-03071-w.
African trypanosomiasis, caused by protozoa of the genus Trypanosoma and transmitted by the tsetse fly, is a serious parasitic disease of humans and animals. Reliable data on the vector distribution, feeding preference and the trypanosome species they carry is pertinent to planning sustainable control strategies.
We deployed 109 biconical traps in 10 villages in two districts of northwestern Uganda to obtain information on the apparent density, trypanosome infection status and blood meal sources of tsetse flies. A subset (272) of the collected samples was analyzed for detection of trypanosomes species and sub-species using a nested PCR protocol based on primers amplifying the Internal Transcribed Spacer (ITS) region of ribosomal DNA. 34 blood-engorged adult tsetse midguts were analyzed for blood meal sources by sequencing of the mitochondrial cytochrome c oxidase 1 (COI) and cytochrome b (cytb) genes.
We captured a total of 622 Glossina fuscipes fuscipes tsetse flies (269 males and 353 females) in the two districts with apparent density (AD) ranging from 0.6 to 3.7 flies/trap/day (FTD). 10.7% (29/272) of the flies were infected with one or more trypanosome species. Infection rate was not significantly associated with district of origin (Generalized linear model (GLM), χ = 0.018, P = 0.895, df = 1, n = 272) and sex of the fly (χ2 = 1.723, P = 0.189, df = 1, n = 272). However, trypanosome infection was highly significantly associated with the fly's age based on wing fray category (χ = 22.374, P < 0.001, df = 1, n = 272), being higher among the very old than the young tsetse. Nested PCR revealed several species of trypanosomes: T. vivax (6.62%), T. congolense (2.57%), T. brucei and T. simiae each at 0.73%. Blood meal analyses revealed five principal vertebrate hosts, namely, cattle (Bos taurus), humans (Homo sapiens), Nile monitor lizard (Varanus niloticus), African mud turtle (Pelusios chapini) and the African Savanna elephant (Loxodonta africana).
We found an infection rate of 10.8% in the tsetse sampled, with all infections attributed to trypanosome species that are causative agents for AAT. However, more verification of this finding using large-scale passive and active screening of human and tsetse samples should be done. Cattle and humans appear to be the most important tsetse hosts in the region and should be considered in the design of control interventions.
非洲锥虫病由锥虫属原生动物引起，通过采采蝇传播，是人和动物的一种严重寄生虫病。有关病媒分布、摄食偏好及其携带的锥虫种类的可靠数据对于制定可持续控制策略至关重要。
我们在乌干达西北部两个区的10个村庄部署了109个双锥形诱捕器，以获取有关采采蝇的表观密度、锥虫感染状况和血餐来源的信息。使用基于扩增核糖体DNA内部转录间隔区（ITS）区域的引物的巢式PCR方案，对收集样本的一个子集（272个）进行分析，以检测锥虫种类和亚种。通过对线粒体细胞色素c氧化酶1（COI）和细胞色素b（cytb）基因进行测序，分析34只饱血成年采采蝇中肠的血餐来源。
我们在这两个区共捕获了622只fuscipesfuscipes采采蝇（269只雄性和353只雌性），表观密度（AD）为0.6至3.7只/诱捕器/天（FTD）。10.7%（29/272）的采采蝇感染了一种或多种锥虫种类。感染率与采采蝇的来源区（广义线性模型（GLM），χ = 0.018，P = 0.895，df = 1，n = 272）和性别（χ2 = 1.723，P = 0.189，df = 1，n = 272）无显著关联。然而，基于翅磨损类别，锥虫感染与采采蝇的年龄高度显著相关（χ = 22.374，P < 0.001，df = 1，n = 272），老龄采采蝇的感染率高于幼龄采采蝇。巢式PCR揭示了几种锥虫种类：活跃锥虫（6.62%）、刚果锥虫（2.57%）、布氏锥虫和西氏锥虫各占0.73%。血餐分析揭示了五种主要脊椎动物宿主，即牛（Bos taurus）、人（Homo sapiens）、尼罗河巨蜥（Varanus niloticus）、非洲泥龟（Pelusios chapini）和非洲草原象（Loxodonta africana）。
我们在所采样的采采蝇中发现感染率为10.8%，所有感染均归因于作为非洲动物锥虫病病原体的锥虫种类。然而，应使用大规模被动和主动筛查人和采采蝇样本对这一发现进行更多验证。牛和人似乎是该地区最重要的采采蝇宿主，在设计控制干预措施时应予以考虑。
