Climate change-induced temperature rise is adding to the spread of the West Nile Virus (WNV) in regions of Europe. The temperature rise has created a favorable condition for the virus and the mosquito vectors to proliferate.
A study conducted by the Institute of Environmental Science and Technology of the Universitat Autònoma de Barcelona (ICTA-UAB) has concluded this fact. The study has analyzed various reasons for the rise of WNV as a major health concern in Europe. The scientists also warn that the virus has the potential to transmit into northern regions of Europe, considering climate warming.
The WNV is a zoonotic vector-borne disease that is generally communicated between birds and mosquitoes. Humans, horses and other mammals can be infected with the virus, but this cannot be transmitted back into the mosquitoes or other organisms. Infected humans can develop serious symptoms, leading to neurological disease or even death.
It is considered that the virus has entered Europe through infected migratory birds in Sub-Saharan Africa. However, the disease has emerged as a serious health concern in Europe considering its spread.
The study was published in the journal One Health.
The researchers endeavored to discover why the disease is prevalent in Europe lately. A huge sum of data for 166 southern and southeastern Europe regions spanning over 13 years was analyzed, which recorded the climate change, land-use pattern, economic changes and government spending in areas such as sanitation and environment.
According to the study’s first author, Matthew Watts, there exists no simple explanation to describe the recent increase of WNV but there are several reasons. Generally, the warmer weather in the spring and summer months due to climate change is causing a favorable condition for the virus and its mosquito, where the mosquito development is leveled up with extension in the breeding season, increasing their numbers.
Significantly, warmer winters likely favored the survival of infected female common house mosquitoes (Culex pipiens) in a location that was previously too cold, like that in northern Italy. Thus, these conditions have helped the mosquitoes survive throughout the winter and spread earlier on in the year.
The outcomes affirmed that areas with a higher proportion of wetlands and arable land, including irrigated agriculture, act as a favorable location to attract susceptible birds and mosquito species, creating a riskier situation to contract the disease.
Shifting over to irrigated from other land-use types would have certainly increased the disease risk, drought may also be increasing the intensity of disease outbreaks, as shrinking water resource means that mosquitoes and birds come into closer contact and therefore increase potential transmission events and hence the prevalence of the virus, which can then spill over into human populations.
Matthew Watts, Study First Author, Institute of Environmental Science and Technology, Universitat Autònoma de Barcelona
All of these environmental changes happened during the austerity period in many countries. Countries with a maximum number of WNV cases are also the ones that cut most of the government infrastructure and hazard prevention spending, for example, environmental protection and wastewater spending. This could have contributed to the increase of vector species and the virus during the critical period.
Watts, M. J., et al. (2021) The rise of West Nile Virus in Southern and Southeastern Europe: A spatial–temporal analysis investigating the combined effects of climate, land use and economic changes. One Health. doi.org/10.1016/j.onehlt.2021.100315.