Swiss dairy herds face new threat from midge-borne orthobunyavirus amidst heatwave

A mysterious illness linked to a new midge-borne virus is affecting Swiss dairy herds for the first time, raising concerns over livestock health amid rising temperatures and no existing vaccine.

Swiss dairy herds are facing an outbreak of illness that veterinary authorities suspect is linked to a midge-borne orthobunyavirus never before detected in the country.

The Federal Food Safety and Veterinary Office said several regions have recorded an increase in sick cows since mid-July, with animals showing fever, diarrhoea and reduced milk output. The Institute of Virology and Immunology has identified an orthobunyavirus from the Simbu group in several acutely affected cattle, although genetic testing is still under way to determine the precise strain and whether it is the direct cause.

The finding matters because Simbu-group viruses are transmitted by biting midges and, according to the office, there is currently no vaccine. The institute said its preliminary results are consistent with evidence emerging in France and Germany, where suspicion is also growing that an orthobunyavirus is circulating in livestock.

Veterinary specialists note that midge-borne viruses are not unusual in animal health. The World Organisation for Animal Health says bluetongue, another midge-transmitted disease, affects domestic and wild ruminants and can reduce productivity, particularly in cattle and sheep. Pirbright Institute research also shows that such infections can damage milk yields and spread quickly in warm conditions.

Swiss officials said it remains unclear whether the current heatwave is contributing to the cases, though high temperatures can intensify stress in high-yielding dairy cows and leave them more vulnerable to disease.

Image Source: Keystone-SDA