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Elevated Plasmodium infection rates and high pyrethroid resistance in major malaria vectors in a forested area of Cameroon highlight challenges of malaria control.

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Ndo, Cyrille, Kopya, Edmond, Donbou, Marie Agathe, Njiokou, Flobert, Awono-Ambene, Parfait and Wondji, Charles ORCID: https://orcid.org/0000-0003-0791-3673 (2018) 'Elevated Plasmodium infection rates and high pyrethroid resistance in major malaria vectors in a forested area of Cameroon highlight challenges of malaria control.'. Parasites & Vectors, Vol 11, Issue 1, p. 157.

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Abstract

High coverage of long-lasting insecticidal nets (LLINs) is the cornerstone of the malaria control strategy of the national malaria control program (NMCP) in Cameroon, with a target of reducing malaria transmission to less than 10% by 2035. To this end, more than 20 million LLINs have been distributed to populations countrywide since 2011. The present study evaluated entomological indices and Anopheles susceptibility to pyrethroids in a rural forested area of south Cameroon with high coverage of LLINs. The study was conducted between July 2014 and May 2016 in Obout, a village located in a rural forested area in south Cameroon. Resting mosquitoes were collected using electric aspirators and were identified to species using morphological criteria and PCR tools. Mosquito feeding preferences and infection status to Plasmodium falciparum were determined by ELISA and using TaqMan assays. The susceptibility of wild F1 adults to pyrethroids was monitored using WHO insecticide susceptibility bioassays. During the study period, 5,993 Anopheles mosquitoes were collected indoors both in rooms with and without nets. Two main vector species, namely An. funestus and An. gambiae, were identified in the locality, with An. funestus being by far the most abundant (89.68%). ELISA analysis revealed high percentage of blood meal taken exclusively on human (97.65-98.95%) supporting the high antropohilic behaviour of both species. Plasmodium falciparum infection rate detected by ELISA was high throughout the study period and varied between 3.28-14.04% (mean: 10.40%) in An. funestus, and between 5.55-22.22% (mean: 13.87%) in An. gambiae. This trend was confirmed by TaqMan assays, with P. falciparum infection prevalence of 23.33% in An. funestus. Significant decrease of mortality associated with high frequency of kdr mutation was observed in An. gambiae (deltamethrin: 36.6-56.45%; permethrin: 6-18.65%) indicating high level of resistance to pyrethroids. For An. funestus, resistance was marked for deltamethrin (mortality: 70.54-76.24%) than for permethrin (94.12-94.74%). Our study showed that despite LLINs, the population of Obout remains exposed to bites of highly infected An. funestus and An. gambiae mosquitoes, highlighting the challenges to controlling malaria in forested areas, especially in the presence of insecticide resistance.

Item Type: Article
Subjects: QV Pharmacology > Anti-Inflammatory Agents. Anti-Infective Agents. Antineoplastic Agents > QV 256 Antimalarials
QX Parasitology > Protozoa > QX 135 Plasmodia
WA Public Health > WA 30 Socioeconomic factors in public health (General)
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 750 Malaria
Faculty: Department: Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI): https://doi.org/10.1186/s13071-018-2759-y
SWORD Depositor: JISC Pubrouter
Depositing User: Stacy Murtagh
Date Deposited: 21 Mar 2018 16:43
Last Modified: 13 Sep 2019 15:48
URI: https://archive.lstmed.ac.uk/id/eprint/8389

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