Objective To investigate the ecological niches of sandflies in the endemic area of visceral leishmaniasis in the extension regions of the Loess Plateau, China, and to determine the infection status of Wolbachia in sandflies. Methods Sandflies were collected in Shan county, Henan province, China (in July 2015) and Yangquan and Wuxiang county, Shanxi province, China (in June and July, 2017). Meanwhile, the habitats were observed and investigated. The sandflies were sorted in the field according to their external morphology; the fresh samples were randomly selected for dissection. The species were identified by observing their pharyngeal armatures and spermathecae. Molecular identification was performed according to partial sequences of the mitochondrial DNA cytochrome b (mtDNA Cyt b) gene. The 16S rRNA fragments of Wolbachia were amplified by PCR to determine the infection status of Wolbachia in sandflies. Results The sites for sandfly collection were typical extension regions of the Loess Plateau with a large area of bare land. A total of 2 273 sandflies were collected in Shan county, Henan province; female sandflies accounted for 79.60% (1 635/2 054) in chicken houses and 93.15%(204/219) in cave dwellings and courtyards, both of which were higher than those of male sandflies. In Yangquan and Wuxiang county, Shanxi province, 3 599 and 2 850 sandflies were captured, respectively. The proportion of female sandflies was much higher than that of male sandflies in both areas. Among the collected sandflies, 99.60%(3 444/3 458) were female sandflies captured in chicken farms and 74.01%(2 549/3 444) of the female sandflies took blood meal. It could be inferred that chickens, sheep, pigs, dogs, ducks, geese, donkeys, and cattle (whether fed concentratedly or scatteredly) in the countryyards were blood source animals for sandflies and the loose soil surrounding those animals were breeding sites for sandflies. All the 50 sandflies identified by morphology were Phlebotomus chinensis. Molecular identification showed that all the 108 sandflies were Ph. chinensis except one that was identified as Sergentomyia squamirostris (found in Shan county, Henan province). Phlebotomus chinensis was the dominant species in the area, and the peak activity season for local sandflies ranged from June to July every year. Wolbachia detection was positive in 9 pooled samples from Shan county, 6 pooled and 56 individual samples from Yangquan city, 10 pooled and 79 individual samples from Wuxiang county. The infection rate for the individual sandfly was 51.85% (56/108) in Yangquan and 73.15% (79/108) in Wuxiang county. Conclusion The ecological niches of vector Ph. chinensis have been identified in the extension regions of the Loess Plateau, which is an important endemic area of leishmaniasis in China. Wolbachia has a high infection rate among the on-site Ph. chinensis population.
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