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The APMEN Vector Control Working Group hosted a webinar recently on the topic of new developments in Indoor Residual Spraying (IRS). We had three international experts on the subject to give presentations covering various aspects of IRS. These were:

1. Dr Iñigo Garmendia – Development of new tools to enable more efficient IRS interventions
2. Dr Muhammad Mukhtar – The role of IRS in Pakistan, in particular during humanitarian crises
3. Dr Manuel Lluberas – The Business Architecture of Indoor Residual Spraying: Sorting out operational details

Insecticide-Treated Nets (ITN’s) and Indoor Residual Spraying (IRS) are the two preferred vector control tools advocated by the World Health Organization for combatting malaria. Globally, ITN’s are by far the favoured intervention, due to cost and labour factors, but IRS still accounts for an estimated 13% of malaria cases averted in Africa where transmission is most intense, according to a 2015 publication by Bhatt et al (1). IRS involves applying residual insecticide to potential vector resting sites on the interior surfaces of human dwellings or other buildings. IRS is also a better option in particular situations for instance during humanitarian crisis.

IRS has been used globally and became one of the preferred vector control methods in some countries. However, due to a higher procurement and operational cost, IRS is not the most preferred method that donors would support. IRS is useful to control not only malaria vector but also mosquito arbovirus vectors, triatomine bugs, and sand flies. This method is considered as one of the best interventions that could bring down malaria case-load quickly as it rapidly reduces adult vector density and longevity for diseases vectors, and does not rely on human behaviour (such as whether to actually use a bednet or not). Quality assurance is needed for IRS operation to reach the most effective and sustainable effects to control the vectors. The IRS quality assurance must address the basic principles such as uniformity, regularity, and completeness. Uniformity means that all surfaces must have consistent application of the required dose of insecticide. Regularity involves repeated implementation of spraying at a regular interval, depending on the local contexts and the length of the transmission period. While completeness indicates all structures should be sprayed thoroughly, including all difficult-to-reach surfaces inside the houses.

To maximize the IRS operation quality checks on spraying tools and operators are needed. Some factors affecting spraying quality need to be considered, such as quality of the spraying tools, insecticide resistance status, spraying operators, and spraying techniques. To get high-quality of spraying tools that eases the job of operators, some public health and chemical companies developed new tools to enable more efficient IRS interventions. Some innovative approaches  such as using mobile and electronic devices have been made available to guide spray operators to spray at the correct distance (for good surface coverage) and speed (for effective spray delivery rate…not too much, not too little) during the IRS operations. The Goizper group developed an electronic device making use of laser technology to measure spraying distance from nozzle to the wall, fluid sensor to measure spraying time of each operator per day and estimate insecticide volume applied by each operator, and mobile application to connect and report the result of spraying quality to supervisors for evaluation purposes.

During humanitarian disasters, IRS is sometimes considered to be the best option for vector control, said Pakistan’s Director of Malaria Control, Dr Muhammad Mukhtar. LLINs deployment was done in the area where almost 30 million people live in temporary shelters during the 2022 flood crisis in Pakistan. However, LLINs could not be used due to space constraints and the inability of hanging the nets in some structures in temporary shelters. It was also reported that many LLINs were damaged, misused, or lost. To bring the malaria caseload reduced, IRS was promoted and implemented in the shelter buildings (schools, hospitals, etc), temporary animal sheds, and tents. This effort brought a significant decline in adult mosquito populations and malaria cases.

It is important to develop a comprehensive and tailored IRS operational plan in a country. In his presentation, Manuel Lluberas (Mosquito Den LLC), emphasized that IRS should consider some components:

• Component 1: Needs Assessment & Design, including training materials, logistic and operational arrangements, etc.
• Component 2: Pre-season, including supervisors recruitment and training, preparation of operators, and logistics, etc.
• Component 3: Campaign design, including stakeholder engagements and consultations, Training of Trainers on spraying use, handling and care, etc.
• Component 4: Staging & Pre-positioning, including spray team recruitment and training, community notification, organise field teams, etc.
• Component 5: Mobilization, including community engagement, IRS implementation, documentation, monitoring and evaluation.
• Component 6: Campaign Closure (demobilize, recover, and evaluate), including review and evaluation, post campaign communications, etc.

The full recording of the webinar is available at https://orene.org/tech_talks/new-developments-in-indoor-residual-spraying/

Useful references:

1. Bhatt, Samir, et al. “The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015.” Nature 526.7572 (2015): 207-211.
2. Operational manual on indoor residual spraying: control of vectors of malaria, Aedes-borne diseases, Chagas disease, leishmaniases and lymphatic filariasis. Geneva: World Health Organization; 2023.
3. Pakistan’s lessons learned on climate change, malaria, and vector-borne disease transmission. https://s3.amazonaws.com/media.unfoundation.org/2023/08/Malaria-Control-Pakistan-Case-Study.pdf