Climate change and the spread of bluetongue disease in Europe
Dr. Diyar Tayeb Barwari
Bluetongue disease is a viral disease transmitted by vector insects and affects all ruminants (such as sheep, cows and goats) and is also transmitted mechanically by biting mosquitoes that transmit the virus from one animal to another.
Historical sources indicate that this disease was endemic in tropical and subtropical regions where the temperature and humidity are suitable for the survival of insects such as mosquitoes. However, this mosquito began to migrate north, targeting the Mediterranean basin and southern Europe in the late 1990s. However, it has practically begun to move further north and has become a threat to many countries in central Europe.
A report published by the World Organisation for Animal Health (OIE), based in Paris, indicates that the challenge of this disease is the multiple serotypes of the virus. Control of bluetongue virus is particularly difficult because it has more than 27 serotypes identified in the World Health Organization’s Wildlife Code, each of which evolves differently in its host. As a result, vaccines or immunity against one serotype do not provide any protection against another. Accordingly, previously recorded epidemic events associated with serotype 8 (seen in European countries between 2007 and 2010) had different epidemiological dynamics than those of serotype 3 (seen in several European countries between September 2023 and October 2024).
In relation to climate change, the report states that with climate change reshaping our environment, the recent emergence of serotype 3 of bluetongue virus in some European countries has raised concerns among farmers and animal health professionals alike, as higher temperatures appear to be increasing the number of insect vectors in new areas, which calls for measures to be taken to protect livestock from bluetongue disease. The spread of bluetongue disease from its origin in North Africa to southern, central and northern Europe is an example of how vectors interact and adapt to climate change, animal density, distribution and movement to change the pattern of the disease. According to the report, data from the World Animal Health Information System (WAHIS) shows that the virus has slowly moved north to central and northern Europe. It was not expected that virus vectors would survive in a situation of lower temperatures and different environments. This change in the distribution of the disease appears to have occurred in 28 European countries, resulting in more than 58,000 unexpected outbreaks between 2007 and 2010. The report indicates that 2023 has seen similar epidemic events in higher latitudes in Europe due to the new serotype of bluetongue virus (serotype 3), which has been reported in several European countries. The report also includes a map of serotype 3 cases in central and northern European countries (Britain, Netherlands, Germany, Sweden, Norway, Denmark, France, Switzerland, Poland, Greece, Portugal, Austria).
It is worth noting that for the disease to be able to spread by insect vectors to a new geographical area, it must be able to survive in that area and adapt to rising temperatures worldwide. As global temperatures rise, we are seeing the spread of bluetongue and other vector-borne diseases (such as Crimean-Congo dengue fever, tick-borne encephalitis, epidemic hemorrhagic fever, and West Nile fever) to temperate regions. This is a cause for concern for animal health and public health professionals, given that about a third of the 91 diseases listed by the World Meteorological Organization in 2024 are vector-borne.
