Environmental statistical modelling of mosquito vectors at different geographical scales

Abstract

Vector-borne diseases are infections transmitted by the bite of infected arthropod vectors, such as mosquitoes, ticks, fleas, midges and flies. Vector-borne diseases pose an increasingly wider threat to global public health, both in terms of people affected and their geographical spread. Mosquitoes are known to be vectors of a large number of pathogens around the globe and are considered as prime candidates for transmitting (re-)emerging vector borne diseases in Europe. Risk maps are a useful tool to assess and visualize the risk of establishment and spread of vector-borne diseases. Knowledge on the spatial distribution of mosquitoes is important to create such a map. In this thesis, statistical models were applied to identify suitable habitats for mosquitoes, at high and low resolution. In the first part of this thesis, the analysis was conducted on indigenous mosquito species (vectors and non-vectors) at a national level (low resolution). The species investigated were Anopheles plumbeus, Culiseta annulata, Anopheles claviger and Ochlerotatus punctor. Different modelling techniques were used to explore the potential spatial distribution in the Netherlands for several indigenous mosquito species. The models were used to investigate which environmental features were associated with the presence of the species, and to produce environmental suitability maps in the Netherlands. In the second part, the focus shifted to urban and suburban areas, and to two potential vector species, i.e., Aedes albopictus and Culex pipiens. Here it was possible to analyse the environment in more detail (at a higher resolution).The habitat preference of the tiger mosquito (Ae. albopictus) is investigated through spatial statistical models that were used to evaluate the relationship between Ae. albopictus egg abundance and land cover types on the campus of Sapienza University in Rome. In the same study area, an estimate of the population abundance of Ae. albopictus based on mark-release-recapture experiments is provided. For this purpose, a novel method is presented. An additional study was conducted in Amsterdam, where the breeding sites of the indigenous mosquito are investigated with the aim of identifying the factors that determine a good larval habitat for these species. Culex pipiens was the most common species. A better understanding of the spatial distribution of vectors is needed to help with successful prevention and control. Here, the feasibility of the ‘‘auto-dissemination’’ approach as a possible alternative to traditional control tools against Ae. albopictus in urban areas is assessed. The approach is based on the assumption that wild adult females, exposed to artificial resting sites contaminated with pyriproxyfen, can disseminate this juvenile hormone analogue to larval habitats, thus interfering with adult emergence. In short, in this thesis, we described tools to gain a better knowledge on the distribution of mosquitoes that are (potential) vector of diseases, using experimental and surveillance data. New knowledge on vectors is necessary to predict the (re-)emergence and spread of vector-borne diseases and to develop new interventions to interrupt or limit the spread of vector-borne diseases.