Tags

Type your tag names separated by a space and hit enter

Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania.
Malar J. 2020 Nov 11; 19(1):408.MJ

Abstract

BACKGROUND

Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used.

METHODS

The study used the World Health Organization (WHO) assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from three villages across two districts in south-eastern Tanzania and included four insecticide classes.

FINDINGS

At baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (> 98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%.

CONCLUSIONS

In south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible.

Authors+Show Affiliations

Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania. ppinda@ihi.or.tz.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania. Swiss Tropical and Public Health Institute, Basel, Switzerland.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania. Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Morogoro, United Republic of Tanzania. fredros@ihi.or.tz. Nelson Mandela African Institution of Science and Technology, School of Life Sciences and Biotechnology, Arusha, United Republic of Tanzania. fredros@ihi.or.tz. School of Public Health, University of the Witwatersrand, Parktown, South Africa. fredros@ihi.or.tz. Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK. fredros@ihi.or.tz.

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

33176805

Citation

Pinda, Polius G., et al. "Comparative Assessment of Insecticide Resistance Phenotypes in Two Major Malaria Vectors, Anopheles Funestus and Anopheles Arabiensis in South-eastern Tanzania." Malaria Journal, vol. 19, no. 1, 2020, p. 408.
Pinda PG, Eichenberger C, Ngowo HS, et al. Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania. Malar J. 2020;19(1):408.
Pinda, P. G., Eichenberger, C., Ngowo, H. S., Msaky, D. S., Abbasi, S., Kihonda, J., Bwanaly, H., & Okumu, F. O. (2020). Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania. Malaria Journal, 19(1), 408. https://doi.org/10.1186/s12936-020-03483-3
Pinda PG, et al. Comparative Assessment of Insecticide Resistance Phenotypes in Two Major Malaria Vectors, Anopheles Funestus and Anopheles Arabiensis in South-eastern Tanzania. Malar J. 2020 Nov 11;19(1):408. PubMed PMID: 33176805.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania. AU - Pinda,Polius G, AU - Eichenberger,Claudia, AU - Ngowo,Halfan S, AU - Msaky,Dickson S, AU - Abbasi,Said, AU - Kihonda,Japhet, AU - Bwanaly,Hamis, AU - Okumu,Fredros O, Y1 - 2020/11/11/ PY - 2020/03/26/received PY - 2020/11/05/accepted PY - 2020/11/12/entrez PY - 2020/11/13/pubmed PY - 2021/6/22/medline KW - Anopheles funestus KW - Ifakara health institute KW - Insecticide resistance KW - PBO KW - Tanzania SP - 408 EP - 408 JF - Malaria journal JO - Malar J VL - 19 IS - 1 N2 - BACKGROUND: Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used. METHODS: The study used the World Health Organization (WHO) assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from three villages across two districts in south-eastern Tanzania and included four insecticide classes. FINDINGS: At baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (> 98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%. CONCLUSIONS: In south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible. SN - 1475-2875 UR - https://www.unboundmedicine.com/medline/citation/33176805/Comparative_assessment_of_insecticide_resistance_phenotypes_in_two_major_malaria_vectors_Anopheles_funestus_and_Anopheles_arabiensis_in_south_eastern_Tanzania_ L2 - https://malariajournal.biomedcentral.com/articles/10.1186/s12936-020-03483-3 DB - PRIME DP - Unbound Medicine ER -