An assessment of Culicoides species as potential vectors of lumpy skin disease in Thailand

Lumpy skin disease (LSD) has recently emerged in southeast Asia and is considered a serious threat to livestock in the Australasian region. Lumpy skin disease virus (LSDV) is transmitted mechanically by a variety of insects including biting flies, mosquitoes and at least one species of Culicoides midge, although the range of potential insect vectors involved is unclear. This disease affects bovids (cattle, buffalo) and is thought to be endemic in Africa. In the past few years LSD has spread via movement of bovids to eastern Russia and eastwards into Asia and most recently into Thailand (March 2021) and Indonesia (February 2022). Whilst mortality is generally less than 10%, the economic and welfare implications of the disease are significant due to reduced production and loss of export market access.
There are some concerns that LSD could spread regionally via windborne spread of biting insects from southeast Asia. Although the larger, heavier, known insect vectors of LSDV (such as the stable fly Stomoxys calcitrans) or implicated vectors (such as tabanid species), are not thought to be dispersed long distances via wind, Culicoides midges could pose a regional risk due to their small size and capacity to travel long distances with wind assistance. If there was spread of LSD into countries close to Australia where competent Culicoides LSDV vectors were present, those Culicoides spp. could potentially carry LSDV into northern Australia, as has been observed with bluetongue virus (BTV) (Eagles et al 2014). LSD would likely be difficult to control without the use of vaccination due to the abundance of many insect vector species in Australia and neighbouring countries (including Culicoides spp.). There are approximately 300 Culicoides spp. in the Australasian region, many of which are also present in Thailand. It is those species whose distribution is continuous between Thailand and Australia that are of greatest concern. As Australia already has strong collaborative links with scientists in Thailand, by working with them, this project provides a great opportunity to better understand the threats LSD and its potential Culicoides vectors pose to Australia and its near neighbours and the potential role of Culicoides in maintaining LSD in Thailand.