Resistance management for sustainable agriculture and improved public health

House mosquito

Culex spp

Mosquitoes of the genus Culex are distributed world-wide and belong to the subfamily Culicinae, which contains several medically important genera. Breeding sites of these mosquitoes are often in collections of water like puddles, ditches or rice-fields but also man-made containers such as tin-cans, bottles or storage tanks. Medically important species like Culex quinquefasciatus or Culex pipiens pipiens prefer to breed in water that is polluted by organic debris such as rotting vegetation or human and animal excrement. Due to their preference for polluted water, larvae of this species are often found in sewer systems, septic tanks or pots containing non-drinkable water. Culex mosquitoes are vectors of filariasis caused by Wuchereria bancrofti or Brugia malayi and of different arboviruses that cause a number of encephalitis diseases as well as Rift-Valley and West Nile fever.

The females of C. quinquefasciatus as well as C. pipiens pipiens are nocturnal, so bite humans preferably in the evening hours or at night. The use of long lasting insecticide impregnated bednets (LLINs) can be an effective method to protect from mosquito bites. Also the use of indoor residual sprays (IRS) is effective, because Culex quinquefasciatus preferably rest indoors after taking a blood meal. Other control methods target the larvae by treating breeding sites with insecticides. Larviciding against Culex larvae often requires a higher dosage of insecticide, because many larvicides are less effective in water that contains organic pollution. Organophosphates and Insect growth regulators (IGRs) are the commonly used classes to treat the breeding sites of Culex mosquitoes as well as products containing Bacillus thuringensis israelensis or Bacillus sphaericus. Other ways of preventing breeding is the improvement and renewing of sanitation systems. Regular visual surveys of possible breeding sites and prompt treatment will aid control.

The WHO has published a resistance monitoring methodology based on a contact bioassay using impregnated filter-papers for adult mosquitoes. The methodology as well as the necessary equipment is available using the links below.

Key house mosquito resources

References

Title Year Author(s) Publisher
The function of two P450s, CYP9M10 and CYP6AA7, in the permethrin resistance of Culex quinquefasciatus Vol. 7(1):587. DOI: 10.1038/s41598-017-00486-0. 2017 Gong Y, Li T, Feng Y, Liu N Scientific Reports
Test procedures for insecticide resistance monitoring in malaria vector mosquitoes (Second edition) Global Malaria Programme 2016 Anon. World Health Organisation
Pyrethroid resistance in Culex pipiens mosquitoes Vol. 120, pp. 68-76 2015 Scott JG, Yoshimizu MH, Kasai S Pesticide Biochemistry and Physiology
Global plan for insecticide resistance management in malaria vectors Global Malaria Programme 2012 Anon. World Health Organisation
Identification of a point mutation in the voltage-gated sodium channel gene of Kenyan Anopheles gambiae associated with resistance to DDT and pyrethroids Vol. 9 (5), pp. 491-497 2000 Ranson H, Jensen B, Vulule JM, Hemingway J, Colins FH Insect Molecular Biology
Voltage-dependent Na+ channels in pyrethroid-resistant Culex pipiens L mosquitoes Vol. 55 (10), pp. 1012-1020 1999 Martinez-Torres D, Chevillon C, Brun-Barale A, Bergé J-B, Pasteur N, Pauron D Pest Management Science
Test procedures for insecticide resistance monitoring in malaria vectors, bio-efficacy and persistence of insecticides on treated surfaces Report of the WHO Informal Consultation 1998 Anon. World Health Organisation

The information provided is based on literature reviews and as such IRAC cannot guarantee or be held accountable for the accuracy of the reports.

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