Impacts of land-use change on mosquito-borne diseases in northern Thailand
(2005)
Files
Vanwambeke.pdf
Restricted Access - Adobe PDF
- 9.54 MB
Details
- Authors
- Supervisors
- Lambin, Eric
- Abstract
- Impacts of land-use change on infectious diseases and more particularly, on vector-borne diseases, are of growing concern. This study investigates the link between vector-borne diseases and land cover: land cover and land use could influence the prevalence of vector-borne diseases by controlling both the spatial distribution and behaviour of vectors, and the degree of exposure of people to contact with vectors according to their activities and socio-economic characteristics. This study investigated, after an in-depth study of land-use changes in northern Thailand, the links between various mosquito species and species groups, and land-cover, and between dengue infection and land cover. Dengue is a major concern in Thailand, where it is a major cause of hospitalisation and death, especially for children. Previously restricted to urban areas, infection prevalence is now high in rural areas as well. Land use and land-use changes were first mapped using remote sensing images. Socio-economic data were collected at the household level in nine villages in Chiang Mai, Lamphun and Mae Hong Son provinces. The observed land-cover changes were then modelled using logistic regression to determine physical factors of change (indicating location of change), and multilevel regression to study socio-economic factors of change (indicating quantity of change). A second step consisted in modelling the probability of the presence of larvae in habitats as a function of land cover. Several land-cover variables derived from the remote-sensing land-cover map were used. This was compared to models including micro-habitat variables. Both series of models used logistic regression and presence/absence of larvae as the dependent variable. Aedes aegypti, Ae. albopictus, Anopheles minimus group, An. maculatus group and An. barbirostris group were studied. A third step tried to understand the direct link between land use and dengue infection risk, as well as to assess risk determinants related to behaviour and use of preventive measures. Using data collected over a three-year long bi-annual survey, land-use maps and multilevel logistic regression, risk factors for dengue seroconversion and seropositivity (for one year) were studied. The analyses were done for two rural and one peri-urban villages in Chiang Mai and Lamphun province. The most important changes observed in rural areas were the intensification of irrigated land by the cultivation of drought-tolerant crops in the dry season, and the expansion of orchards, through upland-field conversions or at the expense of natural vegetation. Production networks at the village level were important for both types of change, and even though the rural sector proves to be investing and getting increasingly market-oriented, increase of existing socio-economic disparities between households is likely. Land cover performed as well as did micro-habitat variables in predicting the presence of mosquito larvae. Land-cover variables act as proxies for the type of habitat available and their attributes, but good knowledge of mosquitoes breeding behaviour is necessary for interpreting the land-cover effects. Direct applicability of these results to other areas is however restricted by potential regional variations in mosquito breeding behaviour, and by variations in the link between habitat availability and land cover, which will be highest for human settlements areas. Risk determinants for seropositivity varied between sites, and environmental factors were more important in rural sites. The largest part of the variation in seroconversion was explained at the time level, possibly relating to the existence of waves in dengue transmission. Location of a person during daytime and in the evening as well as the environment around the house, including irrigated fields and orchards, were important determinants for dengue seroconversion. Generally, the various steps indicated that the link between land use, mosquitoes and diseases is consistent. In a context of important land-use changes as observed in northern Thailand, investigating this link is relevant and could help in designing efficient prevention or control campaigns. ...
- Affiliations
Citations
Vanwambeke, S. (2005). Impacts of land-use change on mosquito-borne diseases in northern Thailand. https://hdl.handle.net/2078.5/124155