Almost half of the midges found on cattle and sheep farms are infected with bluetongue virus serotype 3. This is evidenced by research carried out by the NVWA Centre for Vector Monitoring (NVWA-CMV) and Wageningen Bioveterinary Research (WBVR, part of Wageningen University and Research) on behalf of the Ministry of Agriculture, Nature and Food Quality.
The bluetongue virus serotype (BTV-3) has been circulating in the Netherlands since September 2023. The virus has spread rapidly throughout the country in a short time. Both institutes have investigated which midges are involved in the bluetongue outbreak. To this end, traps have been placed on six livestock farms in the centre of the country where bluetongue has previously been detected.
A total of 34,593 midges were caught. The majority belonged to six species of midges that are naturally found in the Netherlands. The midges breed near livestock and prefer manure and holes. The insects have a strong preference for sheep and cattle. The analysis by WBVR shows that bluetongue virus was present in more than 46 percent of the midges.
Increase in virus circulation
The researchers note that the high proportion of positive midges may be a result of the high rate of virus circulation in the hosts. It may also mean that BTV-3 is well absorbed by these six local midge species. In addition, the high proportion of midges carrying bluetongue may partly explain how the virus was able to spread so quickly across the Netherlands. The percentage of midges testing positive for bluetongue in this study is much higher than during the BTV-8 outbreak in 2006-2008.
On farms where bluetongue is known to be present, the virus has also been found in midges. The researchers concluded that the most common species of midges in livestock are very capable of transmitting the virus. They recommend vaccinating both sheep and cattle as much as possible to prevent bluetongue.
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