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. 2014 May 22:7:236.
doi: 10.1186/1756-3305-7-236.

Impact of PermaNet 3.0 on entomological indices in an area of pyrethroid resistant Anopheles gambiae in south-western Nigeria

Samson T Awolola  1 , Adedapo O Adeogun, Judith B Olojede, Adedayo O Oduola, Isaac O Oyewole, Chioma N Amajoh
Affiliations

Impact of PermaNet 3.0 on entomological indices in an area of pyrethroid resistant Anopheles gambiae in south-western Nigeria

Samson T Awolola et al. Parasit Vectors. .

Abstract

Background: PermaNet® 3.0 is an insecticide synergist-combination long-lasting insecticidal net designed to have increased efficacy against malaria vectors with metabolic resistance, even when combined with kdr. The current study reports on the impact of this improved tool on entomological indices in an area with pyrethroid-resistant malaria vectors in Nigeria.

Methods: Baseline entomological indices across eight villages in Remo North LGA of Ogun State provided the basis for selection of three villages (Ilara, Irolu and Ijesa) for comparing the efficacy of PermaNet® 3.0 (PN3.0), PermaNet® 2.0 (PN2.0) and untreated polyester nets as a control (UTC). In each case, nets were distributed to cover all sleeping spaces and were evaluated for insecticidal activity on a 3-monthly basis. Collection of mosquitoes was conducted monthly via window traps and indoor resting catches. The arithmetic means of mosquito catches per house, entomological inoculation rates before and during the intervention were compared as well as three other outcome parameters: the mean mosquito blood feeding rate, mean mortality and mean parity rates.

Results: Anopheles gambiae s.l. was the main malaria vector in the three villages, accounting for >98% of the Anopheles population and found in appreciable numbers for 6-7 months. Deltamethrin, permethrin and lambdacyhalothrin resistance were confirmed at Ilara, Irolu and Ijesa. The kdr mutation was the sole resistance mechanism at Ilara, whereas kdr plus P450-based metabolic mechanisms were detected at Irolu and Ijesa. Bioassays repeated on domestically used PN 2.0 and PN 3.0 showed persistent optimal (100%) bio-efficacy for both net types after the 3rd, 6th, 9th and 12th month following net distribution. The use of PN 3.0 significantly reduced mosquito densities with a 'mass killing' effect inside houses. Households with PN 3.0 also showed reduced blood feeding as well as lower mosquito parity and sporozoite rates compared to the PN 2.0 and the UTC villages. A significant reduction in the entomological inoculation rate was detected in both the PN 2.0 village (75%) and PN 3.0 village (97%) post LLIN-distribution and not in the UTC village.

Conclusion: The study confirms the efficacy of PN 3.0 in reducing malaria transmission compared to pyrethroid-only LLINs in the presence of malaria vectors with P450-based metabolic- resistance mechanisms.

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Figures

Figure 1
Figure 1
Mean level of P450 monooxygenase activity in pyrethroid resistant Anopheles gambiae s.s . from Ilara, Irolu and Ijesa in relation to the standard reference susceptible Kisumu strain of Anopheles gambiae s.s.
Figure 2
Figure 2
Bio-efficacy of PermaNet 2.0 and PermaNet 3.0 following 0, 3, 6, 9 and 12 months of field usage, as measured against a susceptible strain of Anopheles gambiae s.s (Kisumu) in WHO cone bioassays.
Figure 3
Figure 3
Geometric mean densities of An. gambiae s.s . collected per house at baseline (March 2012) and then monthly for 12-months post intervention at Ilara, Irolu and Ijesa.
Figure 4
Figure 4
Geometric mean of percentage mortality, blood feeding and parity rate for An. gambiae s.s. collected indoor during 12-months post intervention at Ilara, Irolu and Ijesa.
See this image and copyright information in PMC

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