Shlomit Paz (Israel) 1
1 - University of Haifa
Climate change is a driver that influences the epidemiology of vector-borne diseases (VBD) such as malaria, West Nile fever (WNF), dengue or Zika. The life-cycle dynamics of the vector species, pathogenic organisms and the reservoir organisms are sensitive to weather conditions, which affect the survival and reproduction rates of the vectors, their habitat suitability, geographical distribution and abundance, and impact their seasonal intensity and temporal activity.
Recent climatic changes, particularly the increase in ambient temperature and fluctuation in rainfall amounts, contribute to the endemization of VBD such as WNF in various locations around the world.
Today, West Nile Virus (WNV) is the most widely distributed known arbovirus in the world. The virus exists in rural ecosystems as well as in urban areas where mosquitoes breed in organic-rich water. The transmission cycle involve wild birds as the principal hosts and mosquitoes (especially Culex), largely bird-feeding species, as the primary vectors.
WNF is a potentially serious illness for humans and about one in 150 people infected with WNV will develop a severe illness with symptoms that may last several weeks, and the neurological effects may be permanent.
Sporadic cases of WNF were reported in Europe in the past. In summer 2010, the number of cases in Europe was the highest ever reported. This upsurge coincided with extreme hot spells during the preceding summer months. Later, WNF outbreaks during the summers of 2011-2018 occurred in most of the disease locations in 2010.
Abiotic and biotic ecologic factors have both contributed to the endemization of WNV in Europe. These include, in particular, the elevated temperatures.
The impact of precipitation is more complex since the response might vary over different regions, depending on differences in the ecology of mosquito vectors. For example, in a research on mosquito vector populations in the Danube Delta, Romania, negative significant results were detected between precipitation and infection rates.
Monitoring and modelling climatic and environmental conditions permissive for the interaction of migratory birds, resident birds, competent mosquito vectors and humans can help define regions at risk of transmission. Areas at risk should be targeted for integrated surveillance, vector control measures, health system preparedness and public education.
As predictions show that the current climatic trends are expected to continue, for better preparedness, any risk assessment of future transmission of WNV should take into consideration the impacts of climate change.