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Implementing IRM by rotating IRS products with different modes of action 27th September 2022

Indoor residual spraying (IRS) has historically been a powerful malaria vector control intervention. IRS can quickly reduce malaria transmission by reducing adult mosquito vector density and longevity.

The efficacy of IRS for malaria control is threatened by widespread resistance in Anopheline vectors to the limited number of insecticide classes currently approved for public health use. Pyrethroid resistance is present across Africa and resistance to carbamates and organophosphates, which were for many years the only alternative IRS insecticide classes to pyrethroids, is also increasing in Anopheles vector populations. In response to the growing threat of resistance to the efficacy of IRS, the World Health Organization’s (WHO) Global Plan for Insecticide Resistance Management (GPIRM) in Malaria has recommended the use of IRS products containing insecticides with different modes of action in annual rotations.

The use of rotations for IRM relies on the fitness cost that resistance mechanisms have on mosquitoes.  Removing selection pressure exerted by a particular insecticide by switching to alternative insecticide classes will result in the frequency of resistance declining over time. Therefore, IRM based on the rotation of different IRS products will reduce selection pressure for the maintenance of existing insecticide resistance and reduce the speed of development of further resistance. However, implementation of IRS product rotations requires at least three IRS insecticides with different modes of action. This is driving the development of a more diverse portfolio of IRS formulations containing new chemistries which can provide sustained control of insecticide-resistant malaria vector populations.

Broflanilide (TENEBENAL™) is a novel insecticide discovered by Mitsui Chemicals Agro, Inc. (MCAG) which has been formulated as VECTRON™ T500, a wettable powder for IRS. Broflanilide is a meta-diamide insecticide which acts as a non-competitive antagonist of the γ -aminobutyric acid (GABA) receptor of chloride channels of the insect inhibitory nervous system and has been classified by the Insecticide Resistance Action Committee (IRAC) as a GABA-gated chloride channel allosteric modulator (IRAC Group 30). In a collaborative project between MCAG and IVCC, supported by a network of collaborating trials facilities in Africa, the bioefficacy of VECTRON™ T500 has been evaluated in laboratory, experimental hut and community trials. VECTRON™ T500 has demonstrated excellent activity against pyrethroid-resistant strains and populations of Anopheles with residual efficacy of 6 months or more on various wall substrates. These results indicate the potential of VECTRON™ T500 as an addition to the arsenal of IRS products needed to maintain both control of malaria and IRM of malaria-transmitting mosquitoes.

Indoor residual spraying (IRS) is an important topic at this week’s Pan-Africa Mosquito Control Association (PAMCA) Conference, in Rwanda. IVCC team members Graham Small and Janneke Snetselaar will present results on the bioefficacy of VECTRON™ T500 in laboratory, experimental hut and community trials during Parallel Symposium 3: Supporting improved insect resistance management strategies – a new mode of action for Indoor Residual Spray (IRS) programmes (Monday 26th September, 14:00 to 15:30 (GMT+2).


By Graham Small & Janneke Snetselaar
All-Party Parliamentary Group (APPG) visit IVCC – July 2022 22nd July 2022

July 2022

Last week, IVCC was delighted to welcome Catherine West MP, Chair of the All-Party Parliamentary Group (APPG) on Malaria and Neglected Tropical Diseases to Liverpool to meet representatives from IVCC and the Liverpool School of Tropical Medicine (LSTM).

Accompanied by Ian Byrne, MP for Liverpool West Derby and Jeremey Lefroy, founding member of the APPG on Malaria and NTDs and Board member of both LSTM and IVCC, Catherine heard about the innovative vector control pipeline that IVCC is developing and delivering including a new outdoor biting intervention called Attractive Targeted Sugar Bait (ATSB) and BASF’s Interceptor® G2 bed net, a dual-insecticide bed net with an innovative mode of action currently undergoing trials across sub-Saharan Africa. In a recent study published in the Lancet, Interceptor® G2 was able to demonstrate an overall 44% reduction in malaria incidence in children 6 months to 10 years in a random controlled trial conducted in Tanzania, demonstrating the immediate and significant impact innovative tools can have on malaria in endemic countries, particularly against the most vulnerable groups such as young children.

The group also heard about the Access programmes being led by IVCC, such as the NgenIRS programme and the New Nets Project which are helping bring life saving interventions to market at scale and at pace and which are already saved many thousands of lives.

Catherine and guests also visited the Liverpool Insect Testing Establishment (LITE) which supports the testing of insecticide-based products for commercial partners against insecticide-resistant colonies.  LITE maintains a range of insecticide susceptible and resistant colonies of mosquitoes and provides a range of approaches for insecticide efficacy testing. The guests closed the day with a visit to LSTM’s venom unit which houses the largest and most diverse collection of tropical venomous snakes in the UK and leads pioneering research into a universal anti-venom and improvements in the efficacy, affordability and safety of snakebite treatments.

Image: Photo of visit to IVCC by APPG Chair :  Caption of photo;  Catherine West MP (second from left) and Ian Byrne MP (far right) talking to IVCC and LSTM colleagues at the Liverpool Insect Testing Establishment.

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