Outdoor Biting Control

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#IVM #Malaria

The current vector control tools of Indoor Residual Spraying (IRS) and Long Lasting Insecticidal Nets (LLIN) will not lead to malaria eradication on their own, there is an urgent need to control vectors which bite outdoors.

In 2014, IVCC issued a call for proposals to address outdoor biting and awarded grants for Proof of Concept (PoC) demonstrations of targeted insecticidal spraying of Anopheles mating swarms, a push-pull approach to mosquito control, and Attractive Targeted Sugar Baits (ATSB^®).

In addition, IVCC commissioned a series of reviews to explore the gaps and potential for larviciding, aerial and ground space spraying, autodissemination of pyriproxyfen and spatial repellents. These were all focused on African malaria vectors but, in 2018, IVCC was awarded a grant from the Australian government to leverage its African malaria portfolio to assist partners in the Indo-Pacific region where outdoor transmission of malaria and myriad other mosquito-borne diseases is a major public health threat.

Precision Larviciding in Zanzibar

A collaboration of Aberystywyth University, Liverpool School of Tropical Medicine (LSTM), and the Zanzibar Malaria Elimination Programme, this study is a PoC to demonstrate a combination of a state-of-the-art remote sensing system (satellite and drone-based), coupled with an innovative use of smartphone technology.

This smartphone technology offers a more efficient and cost-effective approach to Larval Source Management (LSM) compared to conventional larviciding for eliminating diseases like malaria. It will also provide a tool for the management and supervision of field-based larviciding campaigns, alleviating a well-documented challenge with the implementation of LSM interventions. The system will also improve efficiency of LSM by identifying key habitats where resources can be targeted.

The project will focus on a dry season intervention, targeting persistent mosquito breeding refugia that maintain transmission. The dry season creates a ‘pinch-point’ in vector population dynamics so interventions are likely to lever a significant contribution to elimination. At the end of this PoC stage, a Spatial Intelligence System (SIS) will have been developed and tested.

TEDxAberystwyth, Andy Hardy - Drones gathering spatial intelligence for malaria elimination

Mating Swarms

As part of IVCC’s programme to address outdoor biting, Dr. Diabate in Burkina Faso and Dr. Okumu in Tanzania were funded in 2015 to demonstrate that swarms of dominant malaria vector species can be readily identified and targeted with effective space spraying, to crash their populations significantly and lower their vectorial capacities.

The two groups aimed to demonstrate that swarms could be easily detected and characterized in Tanzania as had already been shown in Burkina Faso, and to assess the impacts of the targeted space spraying of mosquito swarms on densities, age structure, mating, and the malaria transmission intensity in the study villages.

In both locations the teams succeeded in identifying mating swarms and demonstrated that spraying Anopheles swarms reduces vector density and their parity status. While the project proved the method to be technically feasible and effective, the scalability and cost-effectiveness aspects proved to have major challenges. The project ended in early 2018.

Spatial Repellents

Spatial repellents are defined as volatile chemicals that protect against disease vectors, such as mosquitoes, by creating a space where hosts are safe from bites and potential disease transmission.

There is broad consensus that spatial repellents have a place in vector control, but at present most products are targeted to the consumer market and there is limited epidemiological evidence of impact on disease.

Still, current devices may be used in short term or emergency situations including humanitarian relief situations or outbreak response. Spatial repellent devices, with improved duration, may well be suitable to provide indoor and peri-domestic protection perhaps as a replacement or even improvement on IRS.

Push-Pull: Since 2016 IVCC has supported partners at Wageningen University, the Swiss Tropical Public Health Institute and their collaborators at the Ifakara Health Institute, and the International Centre of Insect Physiology and Ecology (ICIPE) (and multiple industrial partners) to investigate the potential to combine a spatial repellent product with a mosquito trap as part of a Push-Pull approach.

The team has tested the individual and combined effects of prototypes of these technologies under semi-field conditions in Kenya and Tanzania and in a pilot field test in Kenya. Results are expected to be published in late 2019.

Attractive Targeted Sugar Bait^®

Female and male mosquitoes need plant-derived sugars and carbohydrates to maintain energy for survival. This almost daily need for sugar presents an opportunity to leverage the sugar feeding process with a bait containing a toxicant.

The basic approach of ATSB^® is to lure mosquitoes or sand flies to a toxic bait and kill them.

Westham has developed a complete product including an attractant, an insecticide and a bait station. In 2016-2017, a partnership between Westham, the Bamako University and IVCC demonstrated a successful proof of concept in 14 villages in Mali. It illustrated this product is having significant impact on mosquito population, decrease in EIR, reduction of survivorship, do not pose significant risk to non-target organisms and is well accepted by communities where deployed.

IVCC and its partners have developed an ambitious development plan to demonstrate that the entomological impact of ATSB^® can be demonstrated in other environments and its public health value. This will be done through randomized controlled trials in several African countries to demonstrate its epidemiological impact.