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Entomological surveys

Copyright Malaria Consortium

Entomological surveys directly study a sampling of mosquitoes in order to provide an understanding of any changes in the characteristics and behaviour of malaria vectors, especially in relation to importance of different vector species in malaria transmission, feeding habits and resistance to insecticides.

How were the entomological surveys conducted?

We used different trapping methods in selected households in each study site to collect and study mosquitoes:

  1. Pyrethrum Spray Collection (PSC) – This method catches mosquitoes resting inside the house
  2. Light Trap Collection (LTC) – This method catches mosquitoes active at night
  3. Exit (window) Trap Collection (ETC) – This method catches mosquitoes as they leave the house through the use of a mesh trap outside windows or openings to the house
  4. Human Landing Collection (HLC) – This method involves catching mosquitoes as they feed from a human host, allowing us to establish biting times inside and outside of the house, as well as other vector habits
  5. Room search – This method is used to catch mosquitoes that have not left the dwelling after the completion of ETC, when PSC has not been used

What data was collected during the entomological survey?

  • Species of mosquitoes
  • Feeding state of mosquitoes
  • Infection state of mosquitoes
  • Phenotypic resistance to insecticides
  • Presence of genetic markers of insecticide resistance

Why is the entomological survey data important?

The effectiveness of malaria interventions relies on an accurate understanding of the characteristics and behaviour of mosquitoes. Entomological surveys are crucial in determining feeding habits and density of different malaria vector species, their age and infection rates, as well as to characterise resistance to currently available insecticides in the study populations.  Any changes need to be identified quickly, so that interventions can be adapted accordingly.

See the figure below for examples of five trapping methods that were used:
From left to right: LTC to collect host-seeking mosquitoes indoors; ETC to collect mosquitoes leaving the house after (un)successful attempt to feed; indoor RMS to collect mosquitoes resting indoors; PSC to collect mosquitoes resting indoors using an insecticide and white sheets spread over the floor surface; HLC to collect host-seeking mosquitoes throughout the night indoors (18:00-06:00) and outdoors (18:00-00:00).

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