To learn about the characteristics of natural foci and the spatial distribution of mosquitoes and ticks in Yadong County, Tibet Autonomous Region (Tibet for short).

The eco-geographical characteristics, demographic information, agricultural and animal husbandry data of the natural foci in Yadong County, Tibet were collected from the Yadong County 2020 statistical yearbook, vector data were collected from the Yadong County Center for Disease Control and Prevention, and the data of the meteorological station in Yadong County from 2010 to 2021 were collected from the World Weather Network. In July 2021, a total of 20 mosquito and tick sampling points were selected for field investigation according to the distribution characteristics of vegetation and animal husbandry of Yadong County. The light trap method was used to trap mosquitoes, and the manual inspection and flag dragging method were used to catch ticks. The spatial distribution characteristics of mosquitoes and ticks were analyzed.

The natural epidemic foci in Yadong County, Tibet, were high in the north and low in the south, with an elevation difference of about 5 000 m. It was rich in water resources, and the average runoff of Yadong River was 20.1 m³/s. The climate in the north was cold and dry, and the south was mild and humid. From 2010 to 2021, the annual average station air pressure in Yadong County was 452.8 mmHg (1 mmHg = 0.133 kPa), the maximum monthly average temperature, precipitation and relative humidity of air were 8.7 ℃, 134.5 mm and 81.3%, respectively, all in July. A total of 6 897 diptera insects were attracted by the light trap method, all of which were non-blood-sucking mosquitoes. The total density was 163.77 pieces/(lamp·h), the dominant population was Muscaridae, accounting for 89.69% (6 186/6 897). In different sampling areas, Xiayadong Township collected the most mosquitoes, accounting for 67.17% (4 633/6 897); the others were Yadong County and Shangyadong Township, accounting for 27.36% (1 887/6 897) and 5.47% (377/6 897), respectively. A total 2 014 host animals were examined, and 23 parasitic ticks were caught, of which 20 were of the genus Ixodes and 3 were of the genus Haemophilus. No free ticks were caught in all ticks sampling points.

The climate and ecological environment of the natural foci in Yadong County, Tibet have obvious vertical gradient. Mosquitoes and ticks are active, but the density is not high, the density of mosquitoes is generally high in the south and low in the north.

Natural foci; Mosquitoes; Ticks