International Centre of Insect Physiology and Ecology, Nairobi, Kenya.
Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa.
PLoS Negl Trop Dis. 2021 Feb 1;15(2):e0009062. doi: 10.1371/journal.pntd.0009062. eCollection 2021 Feb.
Phlebotomine sand flies transmit many viral protozoan and bacterial pathogens of public health importance. Knowledge of the ecologic factors influencing their distribution at local scale can provide insights into disease epidemiology and avenues for targeted control. Animal sheds, termite mounds and houses are important peri-domestic and domestic habitats utilized by different sand flies as resting or breeding habitats. However, our knowledge for selection of these habitats by sand flies remains poor. Here, we tested the hypothesis that these habitat types harbor different composition of sand fly species and differ in their volatile chemistry that could influence sand fly selection. To achieve this, we employed CDC light traps following a cross-sectional survey to investigate the distribution of sand flies in the three habitats in an endemic site for leishmaniasis in Kenya. The study was carried out during the dry season, when sand flies are optimally abundant in 2018 and 2020. Sand fly abundance did not vary between the habitats, but species-specific differences in abundance was evident. Measures of sand fly community structure (Shannon diversity and richness) were highest in animal shed, followed by termite mound and lowest inside human dwelling (house). This finding indicates broader attraction of both sexes of sand flies and females of varying physiological states to animal sheds potentially used as breeding or resting sites, but also as a signal for host presence for a blood meal. Furthermore, gas chromatography-mass spectrometric analysis of volatiles collected from represented substrates associated with these habitats viz: human foot odor on worn socks (houses indoors), cow dung (animal sheds) and termite mounds (enclosed vent), revealed a total of 47 volatile organic compounds. Of these, 26, 35 and 16 were detected in human socks, cow dung and enclosed termite vent, respectively. Of these volatiles, 1-octen-3-ol, 6-methyl-5-hepten-2-one, α-pinene, benzyl alcohol, m-cresol, p-cresol and decanal, previously known as attractants for sandflies and other blood-feeding insects, were common to the habitats. Our results suggest that habitat volatiles may contribute to the composition of sand flies and highlight their potential for use in monitoring sand fly populations.
嗜人按蚊传播许多具有公共卫生重要性的病毒原生动物和细菌病原体。了解影响其在当地尺度分布的生态因素可以深入了解疾病流行病学，并为有针对性的控制提供途径。动物棚、白蚁丘和房屋是不同嗜人按蚊作为休息或繁殖栖息地使用的重要周边和家庭栖息地。然而，我们对这些栖息地被按蚊选择的了解仍然很差。在这里，我们测试了以下假设：这些栖息地类型含有不同的按蚊物种组成，并且在挥发性化学物质方面存在差异，这可能会影响按蚊的选择。为了实现这一目标，我们采用了 CDC 诱捕器，在肯尼亚一个利什曼病流行地区进行了横断面调查，以调查三种栖息地中的按蚊分布。这项研究是在 2018 年和 2020 年干燥季节进行的，此时按蚊数量最佳。三种栖息地之间的按蚊丰度没有差异，但按蚊丰度存在种间差异。按蚊群落结构（香农多样性和丰富度）的衡量指标在动物棚中最高，其次是白蚁丘，在人类住宅（房屋）中最低。这一发现表明，雄性和雌性按蚊以及不同生理状态的雌性对动物棚的吸引力更广泛，动物棚可能被用作繁殖或休息场所，也可能作为宿主存在的信号，以获取血液。此外，对从这些栖息地相关基质中收集的挥发性物质进行气相色谱-质谱分析，即：穿在脚上的袜子上的人体气味（室内房屋）、牛粪（动物棚）和白蚁丘（封闭通风口），共检测到 47 种挥发性有机化合物。其中，在人类袜子、牛粪和封闭的白蚁通风口分别检测到 26、35 和 16 种。在这些挥发性物质中，1-辛烯-3-醇、6-甲基-5-庚烯-2-酮、α-蒎烯、苯甲醇、间甲酚、对甲酚和癸醛，以前被认为是按蚊和其他吸血昆虫的引诱剂，在这些栖息地中是共同的。我们的结果表明，栖息地挥发物可能有助于按蚊的组成，并强调了它们在监测按蚊种群方面的潜在用途。
