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Alternative Methods of Vector Control
Published in Jacques Derek Charlwood, The Ecology of Malaria Vectors, 2019
The recent development of synthetic pyrethroid insecticides, notably metofluthrin and transfluthrin, with high vapour action at ambient temperatures has led to the development of devices that work without requiring the application of heat. There are thousands of registered products that use these active ingredients. There are sophisticated, expensive products that are used in Europe, and there are inexpensive and simpler products (e.g., mosquito coils) that are widely used throughout Africa and Asia. The primary barrier to uptake of these products is cost. They can be produced on plastic lattices or simply on plastic strips and may be effective for several weeks. They have the advantage that they protect a ‘space’ and so are considered to be spatial repellents (SRs). They work by disrupting the orientation of the mosquito towards the host by neural excitation, which occurs at an early stage of pyrethroid toxicity. Spatial repellents work against outdoor/day/early-evening biting mosquitoes – areas of transmission where traditional interventions are not completely effective. SRs show effect against insecticide-resistant populations and might be especially important as non-lethal effects and lowered selection pressure help prevent the emergence/spread of insecticide resistance alleles. SRs should demonstrate added benefit in areas where traditional LLINs or IRS interventions may not offer full protection or have reached their efficacy limits – especially in areas with residual transmission. Spatial repellents are an obvious area where improvements and developments will take place. A single emanator of metofluthrin reduced landing rates by 48% in Cambodia – good, but no cigar as they say.
Clinical presentation of type 1 and type 2 pyrethroid poisoning in humans
Published in Clinical Toxicology, 2022
Manna Sera Jacob, Ramya Iyyadurai, Arun Jose, Jude Joseph Fleming, Grace Rebekah, Anand Zachariah, Samuel George Hansdak, Reginald Alex, Vignesh Kumar Chandiraseharan, Audrin Lenin, John Victor Peter
At presentation, 14 patients were identified as having taken type 1 pyrethroid compounds and 42 patients had ingested type 2 compounds. An additional 3 patients with unknown poisoning were identified as type 1 pyrethroid poisoning (n = 2) and type 2 pyrethroid poisoning (n = 1). The cohort thus comprised 16 patients with type 1 poisoning and 43 patients with type 2 poisoning. The compounds included (Figure 1) cypermethrin (n = 18), lambda-cyhalothrin (n = 14) and transfluthrin (n = 12). All pyrethroid preparations implicated in poisoning were agricultural formulations except transfluthrin which is marketed as a mosquito repellent mixed with the solvent kerosene.