Testing bio-efficacy of insecticide-treated nets with fewer mosquitoes for enhanced malaria control

Boyer, Sébastien; Pothin, Emilie; Randriamaherijaona, Sanjiarizaha; Rogier, Christophe; Kesteman, Thomas

doi:10.1038/s41598-018-34979-3

Cited by 6 publications

(5 citation statements)

References 12 publications

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“…Malaria control programmes implementing LLINs as primary vector control strategy are required to monitor the survival of nets, fabric integrity and insecticidal efficacy so as to ensure timely replacement of nets [21].…”

Section: Discussionmentioning

confidence: 99%

Evaluation of bio-efficacy and durability of long-lasting insecticidal nets distributed by malaria elimination programme in Eastern India

Sahu

Keshaowar

Thankachy

et al. 2020

Malar J

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Background Long-lasting insecticidal nets (LLINs) are the most favoured vector control tools worldwide. Timely monitoring and evaluation of LLINs is important to sustain the impact of this promising vector control method and for replacement of worn-out and those rendered ineffective. During the mid-2017, LLINs were distributed by the National Vector Borne Disease Control Programme (NVBDCP) in high malaria endemic districts of the eastern coastal state of Odisha. The study was carried out to assess the field performance of the LLINs post 30 months of distribution in Koraput district of Odisha state. Methods A total of 130 households were randomly selected from three villages of Laxmipur CHC in Koraput district, Odisha, India; one each from hilltop, foothill and plain terrain. The net users were interviewed to elicit information on usage, washing practices, physical integrity, bio-efficacy and survivorship of LLINs to confirm the claimed three-year life of the LLINs. Results 74.8% of the LLINs were physically present after 30 months of distribution. The numbers (%) of LLINs used previous night varied from 30 to 61% between study villages. 74% respondents were using the LLINs throughout the year and 26% only seasonally. Of the total, 85% of the nets were reported to be washed and 95% nets were dried under shade as recommended. Altogether, 58% of the surveyed nets were found torn with holes. Of these, 74 (57%) nets were in good condition, 10 (8%) nets were in serviceable and 45 (35%) nets were badly torn and needed replacement. A total of 45 (93.75%), 68 (80%) and 71 (63.8%) LLINs were physically present in hilltop, foothill and plain villages, respectively. The LLINs did meet the efficacy criteria, given the 100% mortality to the exposed Anopheles jeyporiensis mosquitoes post 30 months distribution. Conclusions The findings of this study were communicated to the programme officials of the state and LLINs were replenished soon after 31st month post-distribution of LLINs.

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Section: Discussionmentioning

confidence: 99%

Evaluation of bio-efficacy and durability of long-lasting insecticidal nets distributed by malaria elimination programme in Eastern India

Sahu

Keshaowar

Thankachy

et al. 2020

Malar J

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“…WHO cone bioassays were conducted on the LLINs according to WHO guidelines 23,24 , using 25 (as recommended in ref. 37 ) fully pyrethroid susceptible An. farauti mosquitoes.…”

Section: Methodsmentioning

confidence: 99%

Decreased bioefficacy of long-lasting insecticidal nets and the resurgence of malaria in Papua New Guinea

et al. 2020

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Papua New Guinea (PNG) has the highest malaria transmission outside of Africa. Longlasting insecticidal nets (LLINs) are believed to have helped to reduce average malaria prevalence in PNG from 16% in 2008 to 1% in 2014. Since 2015 malaria in PNG has resurged significantly. Here, we present observations documenting decreased bioefficacy of unused LLINs with manufacturing dates between 2013 and 2019 collected from villages and LLIN distributors in PNG. Specifically, we show that of n = 167 tested LLINs manufactured after 2013, only 17% are fulfilling the required World Health Organisation bioefficacy standards of ≥ 80% 24 h mortality or ≥ 95% 60 min knockdown in bioassays with pyrethroid susceptible Anopheles farauti mosquitoes. In contrast, all (100%, n = 25) LLINs with manufacturing dates prior to 2013 are meeting these bioefficacy standards. These results suggest that decreased bioefficacy of LLINs is contributing to the malaria resurgence in PNG and increased scrutiny of LLIN quality is warranted.

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“…World Health Organisation (WHO) cone bioassays were conducted on these LLINs according to standard protocol, using either 50 or 25 (as recommended in [24]) fully pyrethroid susceptible Anopheles farauti mosquitoes either from a mosquito colony established at PNGIMR or collected locally as larvae and reared to adult stage. The experimental setup is shown in Figure 1.…”

Section: Methodsmentioning

confidence: 99%

“…World Health Organisation (WHO) cone bioassays were conducted on these LLINs according to standard protocol, using either 50 or 25 (as recommended in [24]…”

Section: Cone Bioassaysmentioning

confidence: 99%

Decreased bioefficacy of long-lasting insecticidal nets and the resurgence of malaria in Papua New Guinea

Vinit

Timinao

Bubun

et al. 2020

Preprint

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Background: Papua New Guinea (PNG) has the highest malaria transmission outside of Africa and long-lasting insecticidal nets (LLIN) are the only vector-control tool distributed country-wide. LLIN were introduced into PNG in about 2005 and have been attributed to have had a huge impact on malaria transmission, with reductions in malaria prevalence observed from 15.7% (2008) to 1% (2014). Since 2015, malaria indicators in PNG have risen significantly. Similar trends have been observed in several African nations. In the present study, we observed a drastic reduction in bioefficacy of LLIN collected both from communities (used nets) and prior to use (new nets). We hypothesise that decreased bioefficacy of LLINs is a major contributor to the observed malaria resurgence in PNG and possibly in other parts of the world. Methods: New LLIN in original and unopened packaging (n=192) with a range of manufacturing dates from 2007-2019 were collected either directly from consignments or from households in 15 PNG provinces. Used LLIN (n=40) were collected in 2 provinces, with manufacturing dates ranging from 2008-2017. LLIN were subjected to standard WHO cone bioassays using fully susceptible An. farauti mosquitoes. A subset of LLIN was re-tested using fully susceptible An. gambiae mosquitoes in order to ensure reproducibility of results. Results: Only 7% (95% CI 4-12%) of new LLIN manufactured between 2013-2019 exhibited 100% mortality. However, 84% (95%CI: 65-84%) new nets manufactured in 2012 or before exhibited 100% mortality. Only 29 % of used LLIN less than 3 years old exhibited > 80% 24h-mortality. Results obtained in tests using An. farauti corresponded well with confirmatory tests conducted using An. gambiae. Discussion: Bioefficacy of LLIN in PNG appears to have been highly variable since 2013, with few nets manufactured since 2013 meeting WHO standards. This time-frame coincides with malaria resurgence in the country. These results may have ramifications for LLIN-based malaria control that go beyond the local PNG scenario.

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Testing bio-efficacy of insecticide-treated nets with fewer mosquitoes for enhanced malaria control

Cited by 6 publications

References 12 publications

Evaluation of bio-efficacy and durability of long-lasting insecticidal nets distributed by malaria elimination programme in Eastern India

Evaluation of bio-efficacy and durability of long-lasting insecticidal nets distributed by malaria elimination programme in Eastern India

Decreased bioefficacy of long-lasting insecticidal nets and the resurgence of malaria in Papua New Guinea

Decreased bioefficacy of long-lasting insecticidal nets and the resurgence of malaria in Papua New Guinea

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