Influence of testing modality on bioefficacy for the evaluation of Interceptor^® G2 mosquito nets to combat malaria mosquitoes in Tanzania

Area of Science:

• Medical Entomology
• Public Health
• Vector Control

Background:

• Insecticide-treated net (ITN) durability is crucial for malaria control.
• Interceptor G2 is a dual-adulticide ITN (alpha-cypermethrin and chlorfenapyr) designed for insecticide resistance management.
• Chlorfenapyr is a pro-insecticide activated by mosquito metabolic enzymes.

Purpose of the Study:

• To compare the efficacy of Interceptor G2 against Interceptor ITNs against local mosquito strains in Tanzania.
• To investigate the impact of different bioassay modalities on ITN performance evaluation.
• To assess the effectiveness of Interceptor G2 in managing insecticide resistance.

Main Methods:

• Evaluated Interceptor G2 and Interceptor ITNs against pyrethroid-resistant Anopheles arabiensis and Culex quinquefasciatus, and susceptible Anopheles gambiae and Aedes aegypti.
• Tested both unwashed and 20x washed nets.
• Utilized four bioassay types: WHO cone test, WHO tunnel test, Ifakara ambient chamber test (I-ACT), and WHO experimental hut test (hut).

Main Results:

• Interceptor G2 demonstrated superiority over Interceptor in free-flying bioassays (tunnel, I-ACT, hut) against resistant strains.
• In cone tests, which restrict mosquito movement, Interceptor showed superiority over Interceptor G2.
• Both ITNs exhibited high blood-feeding inhibition, with Interceptor G2 showing higher mortality odds in free-flying tests.

Conclusions:

• Free-flying laboratory bioassays (WHO Tunnel and I-ACT) correlate well with experimental hut test results.
• The I-ACT offers a potential alternative for in situ ITN bioefficacy monitoring with enhanced statistical power.
• Interceptor G2 effectively combats pyrethroid-resistant mosquito strains, highlighting chlorfenapyr's role in malaria mitigation.