School of Life Sciences, University of KwaZulu-Natal, Durban, South Africa.
Department of Veterinary Services, Ministry of Fisheries and Livestock, Lusaka, Zambia.
Trop Anim Health Prod. 2021 May 5;53(2):305. doi: 10.1007/s11250-021-02749-5.
Occurrence of nutritional stress (due to depletion of fat reserves) in tsetse flies, associated with inadequate levels of access to blood meals, enhances susceptibility of the flies to trypanosome infection. Thus, in a tsetse-infested area, a spatial gradient of reducing tsetse habitat quality is potentially a gradient of increasing prospects for occurrence of stress in tsetse flies. This study investigated prevalence of trypanosome infection in Glossina morsitans morsitans and G. pallidipes along a transect line hypothesised to represent such a gradient, in relation to the edge of the tsetse belt and distribution of human settlements. This was undertaken in three sites located in Lundazi, Mpika and Rufunsa districts, respectively, in north-eastern Zambia. Human settlement was concentrated at the edge of the tsetse belt in the Mpika and Rufunsa sites and evenly distributed along transect line in the Lundazi site. Tsetse fly samples were collected using black-screen fly rounds and Epsilon traps. Detection of trypanosome infection was by dissection and microscopy in Lundazi and Mpika sites and loop-mediated isothermal amplification (LAMP) test in Rufunsa site. Multiple logistic regression models were applied to determine whether the following factors, 'change in distance from edge of tsetse belt', 'tsetse sampling method' and 'sex of tsetse fly', had effect on 'prevalence of trypanosome infection' in the tsetse flies. Only 'increase in distance from the edge of tsetse belt' for G. m. morsitans was significantly associated with 'prevalence of trypanosome infection' in the flies, in the Mpika and Rufunsa sites. Distance was associated with reduced likelihood of infection with 'one or more subgenera of trypanosomes' and with 'Nannomonas trypanosomes', in the case of 'all sites collectively', 'Lundazi and Mpika sites collectively', Mpika site alone, and Rufunsa site alone. Per site, increase in distance entailed reduced prospects for Trypanozoon infection but only in the Mpika and Rufunsa sites. We conclude that in the Mpika and Rufunsa sites, increase in distance from human settlements entailed reduced likelihood of trypanosome infection, likely due to reducing tsetse habitat degradation, increasing availability of hosts, and hence increasing levels of nutrition and fat reserves, thus enhancing tsetse immunity against trypanosome infection.
营养压力（由于脂肪储备枯竭）的发生与采血量不足有关，会增加采采蝇感染锥虫的易感性。因此，在采采蝇肆虐的地区，采采蝇栖息地质量降低的空间梯度可能是采采蝇发生压力增加的梯度。本研究调查了 Glossina morsitans morsitans 和 G. pallidipes 中锥虫感染的流行情况，这些地区沿着假设的梯度线分布，与采采蝇带的边缘和人类住区的分布有关。这是在赞比亚东北部的 Lundazi、Mpika 和 Rufunsa 区的三个地点进行的。人类住区集中在 Mpika 和 Rufunsa 地点的采采蝇带边缘，而在 Lundazi 地点则均匀分布在梯度线上。使用黑色屏幕蝇圈和 Epsilon 陷阱采集采采蝇样本。在 Lundazi 和 Mpika 地点通过解剖和显微镜检测锥虫感染，在 Rufunsa 地点通过环介导等温扩增（LAMP）试验检测。应用多元逻辑回归模型来确定以下因素，即“距采采蝇带边缘的距离变化”、“采采蝇采样方法”和“采采蝇性别”是否对采采蝇中的“锥虫感染率”有影响。只有“距采采蝇带边缘的距离增加”与 Mpika 和 Rufunsa 地点的 G. m. morsitans 中的“锥虫感染率”显著相关。距离与“一种或多种锥虫亚属”和“Nannomonas trypanosomes”的感染可能性降低有关，对于“所有地点”、“Lundazi 和 Mpika 地点”、“Mpika 地点”和“Rufunsa 地点”。每个地点，距离的增加都意味着 Trypanozoon 感染的可能性降低，但仅限于 Mpika 和 Rufunsa 地点。我们得出结论，在 Mpika 和 Rufunsa 地点，距离人类住区的增加意味着锥虫感染的可能性降低，这可能是由于减少了采采蝇栖息地的退化，增加了宿主的可用性，从而增加了营养和脂肪储备，从而增强了采采蝇对锥虫感染的免疫力。
