Climate change and vector‐borne viral diseases potentially transmitted by transfusion

Abstract

Vector‐borne diseases occur when infectious agents (virus, protozoa, bacteria, or helminthes) are transmitted to their hosts by a carrier organism. Climate conditions and their changes play a role in the inter‐relationship between these agents, the vectors and the host (or hosts). This review is focused on arthropod‐borne viruses (Arboviruses). These viruses are transmitted between susceptible vertebrate hosts by blood‐feeding arthropods, and may be transmitted by blood transfusion, tissue and organ transplantation and breast feeding. The lifecycle of arboviruses is influenced by changes in temperature, rainfall, humidity, length of day, average daily solar radiation and/or storm patterns, as well as changes in the frequency of rare events such as floods or droughts. A plethora of studies have suggested that climate changes, particularly temperature changes, are likely to be induced by increase in the amount of greenhouse gases, such as methane, carbon dioxide (CO2) and chlorofluorocarbons, which deplete ozone in the atmosphere leading to an increase in ultraviolet radiation. Current models predict that ambient temperature will increase by 3–5°C on average with a doubling in CO2concentration in the atmosphere. Vectors, pathogens and hosts each survive and reproduce within a range of optimal climatic conditions: temperature and precipitation being most important, while sea level elevation, wind and daylight duration are also important. Climate changes may affect important determinants of vector‐borne disease transmission including (i) vector survival and reproduction, (ii) the vector's biting rate, and (iii) the pathogen's incubation rate within the vector organism. Droughts can increase the dissemination of arboviral diseases in urban areas by allowing a boost in the population of mosquitoes in foul water concentrated in catch basins where they breed. Furthermore, eggs can be vertically infected with arboviruses and heat waves speed up the maturation of the mosquitoes and of the viruses within mosquitoes. Droughts also cause a decline in mosquito predators like frogs, darning needles and dragonflies. In addition, birds congregate around shrinking water sites, enhancing circulation of viruses among birds and mosquitoes. In conclusion, the seriousness of some of the recent epidemics like West Nile virus and Dengue appear to has been influenced by climate change. As most of the arboviral infections are asymptomatic in humans, there is an increased opportunity for blood, organ and tissue donations by infected individuals during the viraemic period, resulting in an increased risk of transmission of arboviruses.