Mosquitoes

Last update: 15 March 2011

EDENext’s mosquito-borne diseases (MBD) group will be focusing on two particular diseases. West Nile virus (WNV) was addressed in the EDEN project but a lot of research is still needed for a better understanding of its epidemiology and the risk of large-scale spread in Europe. Recent outbreaks in Italy and the emergence of WN virus lineage 2 in Hungary and Austria have raised public health concerns. The recent Chikungunya outbreak in Italy has revealed the epidemic potential of Aedes albopictus (and other invasive mosquito species such as Ae. japonicus) as a vector for Chikungunya virus and other arboviruses such as dengue.

Zoonotic diseases are fascinating because they are complex, and WNV may be one of the most complex of all. It is essentially a migratory virus, one that may be more versatile than others because it must be infective to local fauna wherever it travels. EDENext will be examining the lack of host specificity for WNV, noting that although it is regarded as a mosquito-borne avian virus, it is known to be highly infective by the oral and mucosal route and can infect mammals, reptiles and amphibians; moreover, it can survive as a chronic infection and be shed in the excreta and urine of birds and mammals long after viraemia has subsided, yet such details have been largely ignored in studies of its transmission in nature.

This will be the principal theme of EDENext’s work on WNV: if such routes of transmission are significant in nature, and if chronic infections are common, we face a host of alternative cycles of transmission that do not involve arthropods at all. The second theme is the survival of virus in winter, when mosquitoes are inactive. During the EDEN project WNV was isolated from overwintering mosquitoes and we know these feed on sugar, not blood, in preparation for diapause, so infection must be vertical, via the egg stage. This may be significant as an overwintering strategy, and indeed at other times of the year, but has not yet been studied in the field. These two themes imply that overwintering vectors and chronically infected vertebrate hosts should both be reviewed as reservoirs: both may function as repositories for virus over extended periods of time when mosquitoes are not active.

EDENext believes many factors will determine the future expansion of Aedes albopictus and Ae. japonicus. Climatic conditions are a key parameter that we can study in advance and EDENext will focus on the effects of temperature on the basic bionomics: development rate, productivity of breeding sites, survival and diapause. The rate of viral replication will also be studied as previous studies have been conducted at constant temperatures and this is certainly not the case in nature.

Last update: 15 March 2011

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