Changes in abundance and behaviour of vector mosquitoes induced by land use during the development of an oil palm plantation in Sarawak

Abstract

Surveys were conducted of adult and immature mosquitoes in an area undergoing oil palm development in north Sarawak. Point prevalence data from 2 sites were collected annually, coinciding with annual phases of forest clearing, burning/cultivation, and maintenance. Major habitat perturbation during the forest/clearing transition shifted the major mosquito faunal equilibrium in terms of species composition, relative density and occurrence. Analyses of variance showed that the mean numbers of 4 species of Anopheles decreased significantly after forest clearing. Relative densities of immature stages decreased after forest clearing, but A. letifer and Culex tritaeniorhynchus remained relatively unchanged after the second year. Comparisons with the pre-development forest stage showed that the reductions in person-biting rates, adult survival and combined entomological inoculation rates (EIR) of A. donaldi and A. letifer decreased the risk of malaria transmission by 90% over the 4 years period. Concomitant reductions in EIR and annual malaria incidence were also correlated. This study highlighted the 'law of unintended consequences', since 2 contrasting effects were observed: reduction of malaria vectors but concomitant increase of dengue vectors.

The Global Public Health Significance of Plasmodium vivax

“…Specimens collected in Sarawak, Malaysia were found to be sporozoite positive and although the species of the parasite was not identified, >90% of the malaria infections in the region at the time were due to P. vivax (Chang et al, 1997). Implied transmission, but with no direct evidence, is described in other references (Rahman et al, 1997;Fryauff et al, 1998 (Seng et al, 1999).…”

Systematic review of effects on biodiversity from oil palm production

“…All except one study were site comparisons between oil palm plantation and primary or secondary forest or both. In the one before-and-after study Chang et al [27] studied changes in abundance of mosquitoes induced by land use change during the development of an oil palm plantation.…”

Establishing the evidence base for maintaining biodiversity and ecosystem function in the oil palm landscapes of South East Asia

“…Note that we do not include studies where collection methods differed between habitats or those that do not provide abundance data. Data sources: ants 1 [14]; ants 2 [15]; bats [16]; bees [17]; beetles [18]; birds [19]; dung beetles [20]; isopods [21]; lizards [22]; mosquitoes [23]; moths [24]; primates [16]; small mammals [25].…”