According to researchers from Kenya, Tanzania and the United Kingdom, it is difficult, labour-intensive and expensive to measure the impact of interventions that aim to decrease the populations of disease-transmitting insects such as mosquitoes partly because of their abundance, seasonal changes and different collection methods.
“All the people who live in malaria endemic areas and who are exposed to malaria will benefit from these findings.”
Charles Mbogo, Kenya Medical Research Institute
Therefore, they used simulations to assess the decline of mosquito populations resulting from vector control interventions in Kilifi, Kenya and compared it to that of a similar malaria population in Tanzania, which had not been adequately controlled by interventions such as insecticide-treated bed nets.
Charles Mbogo, a co-author of the study and a public health entomologist at Kenya-based Kenya Medical Research Institute, tells SciDev.Net that the main objective of the study was to describe the population genetics of Anopheles mosquitoes along the Kenyan coast and to demonstrate the effectiveness malaria control measures such as use of treated bed nets.
The researchers collected samples of malaria-causing mosquitoes — Anopheles gambiae, A. arabiensis and A. merus in Kilifi district, Kenya and two Tanzanian villages from 2008 to 2010. They analysed the genetic components of the mosquitoes and used simulations to estimate the decline in mosquito populations.
Based on their modelling study, the researchers estimate that a starting population of one million mosquitoes per square kilometres in Kilifi, where interventions to control the mosquitoes have been implemented, might have been reduced to just 30 mosquitoes per square kilometres.
“Measuring population genomic parameters in a small sample of individuals [mosquitoes] before, during and after vector or pest control may be a valuable method of tracking the effectiveness of interventions,” the researchers note in the study published in the Malaria Journal last month (24 March).
“All the people who live in malaria endemic areas and who are exposed to malaria will benefit from these findings,” Mbogo adds. Charles Chunge, director of Kenya-based Centre for Tropical and Travel Medicine, says the study shows that the intervention is effectively interfering with the genetic materials of the mosquito.
The trouble is that this type of mosquito could be more infectious in the spread of malaria, adds Chunge.
According to John Logedi, a deputy-director of medical services at Kenya’s Ministry of Health, there has been a decline in populations of A. gambiae while populations of A. arabiensis and A. merus have been increasing in the country.
Logedi tells SciDev.Net that even though the study gives an indication that the intervention seems to be working, more studies are needed of similar nature.
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.