Diversity and seasonal abundance of Culicoides (Diptera, Ceratopogonidae) in Shizong County, Yunnan Province, China

Abstract

Culicoides (Diptera, Ceratopogonidae) are small biting midges, some of which are vectors for animal associated arboviruses such as bluetongue virus (BTV) and Akabane virus (AKAV). BTV and AKAV are both pathogenic for livestock, with BTV in particular posing a major threat to domestic ruminants. Ongoing problems with BTV in ruminants in Shizong County of Yunnan Province, China, promoted a year-long investigation of the Culicoides in Shizong to determine relative abundance and seasonality of midges and to attempt to identify species that might be acting as vectors in the area. Culicoides were collected by UV light trap for one night per week for most weeks between May 2020 and May 2021. More than 21,000 specimens consisting of at least 21 species belonging to six subgenera and one unplaced group, including 5 species previously associated with BTV and one associated with AKAV, were collected. Culicoides tainanus dominated most collections throughout the year although C. sumatrae was often the dominant species over summer. Most species were abundant between May and October. These results indicate that C. tainanus, C. jacobsoni and C. oxystoma are the major midge pests of livestock in Shizong and should be considered in any disease investigation.

Keywords: BTV; China; Culicoides; Seasonal abundance; Vector; Yunnan.

Figure 1

Sketch Map. The collection site (Shizong) and BTV associated provinces, as well as some neighbouring countries are labeled.

Figure 2

Photographs of representative female wings of the 21 Culicoides species collected at Wulong, Shizong County, Yunnan Province, China. Scale bar length = 250 μm.

Figure 3

Heatmap of Culicoides abundance in collections from Wulong, Shizong County, Yunnan Province, China between May 20, 2020 and May 27, 2021. Known or suspected vectors of BTV are highlighted in red. S1, S2, S3, S4 and S5 represent the Culicoides subgenera Remmia, Culicoides, Trithecoides, Meijerehelea, and the Clavipalpis group, respectively.

Figure 4

Seasonal abundance of Culicoides. A) Relative monthly abundance of Culicoides at Wulong, Shizong County, Yunnan Province, China between May 2020 and May 2021. Note that no trapping was done between 15 Jan and 20 Mar 2021; B) average Culicoides amount of each batch of collection every month; and C) average monthly maximum temperatures (TEM, red line) and minimum temperatures (blue line) and the number of the days per month experiencing one of the five precipitation categories. The period in 2021 is highlighted in a grey background.

Figure 5

Average monthly numbers of potential BTV vector species at Wulong, Shizong, Yunnan Province, China between May 2020 and May 2021. Logarithm axe and midge amounts (n + 1) are shown on the y-axis. The period in 2021 is highlighted in a grey background.

Figure S1:

Diversity and relative abundance of specimens belonging to subgenera collected at Wulong between 2020 and 2021. (A) Proportion of Culicoides specimens belonging to species from different subgenera or groups; (B) number of species belonging to each subgenus.