insecticide's effect

Pyrethroid Insecticide Formulations

2009-02-25T20:56:00.000-08:00

Comparative evaluation of pyrethroid insecticide formulations against Triatoma infestans

We investigated the residual efficacy of four insecticide formulations used in Chagas disease vector control campaigns: cyfluthrin 12.5% suspension concentrace (SC), lambda-cyhalothrin 10% wettable powder (WP), deltamethrin 2.5% SC, and 2.5% WP on four types of circular blocks of wood, straw with mud, straw with mud painted with lime, and mud containing 5% of cement. Three concentrations of these insecticides were tested: the LC90 (previously determined on filter paper), the double of the LC90, and the recommended operational dose. For each bioassay test, 15 third-stage nymphs of Triatoma infestans (Klug) (Hemiptera: Reduviidae) were exposed for 120 h to each treatment at 24 h, 30, 60, 90, and 180 days post-spraying. Mortality rates, moulting history and behaviour were recorded at 24, 48, 72, and 120 h of exposure. Mortality rates were highest during the first 30 days post-spraying. Highest mortality rates (above 50%) were observed for deltamethrin 2.5% SC and lambda-cyhalothrin 10% WP on wood blocks up to three months post-spraying. Mud was the substrate on which treatments showed lowest persistence, with the other two substrates showing intermediate residual efficacy of all treatments. During the first 30 days WP formulations were not as effective as SC flowable formulations but, overall in the longer term, WP gave grater mortality rates of T. infestans nymphs exposed at up to six months post-spraying. Porous surfaces, especially mud, showed most variability presumably due to absorption of the insecticide. In contrast the less porous surfaces (i.e. wood and lime-coated mud) kept mortality rates high for longer post-treatment, irrespective of the insecticide concentration used.

Treated Mosquito Nets

2009-02-25T20:42:00.000-08:00

Insecticide-Treated Mosquito Nets

The President’s Malaria Initiative (PMI) – a collaborative U.S. Government effort led by USAID in conjunction with the Department of Health and Human Services (Centers for Disease Control and Prevention), the Department of State, the White House, and others – uses a comprehensive and sustainable approach to saving lives. This includes the purchase and distribution of medicines for treatment; distribution of medicines for prevention of malaria in pregnancy; and both the spraying of residual insecticides on the indoor surfaces of dwellings in selected areas and the improved access to insecticide-treated nets, either through direct distribution, or targeted subsidies.

Insecticide-treated mosquito nets, or ITNs, are one of the most effective methods to prevent malaria in sub-Saharan Africa, where over a million people die every year as a result of the disease – the majority of its victims being pregnant women and children under five years of age. Pregnant women and children benefit the most from the use of ITNs. By promoting the widespread use of ITNs and recommending that pregnant women and small children sleep under the nets to help prevent malaria, PMI is helping to protect millions of children and mothers in Africa from one of the most serious threats to their survival.

A simple mosquito net treated with an insecticide is a proven and cost-effective way to repel or kill mosquitoes carrying the parasite that causes malaria. Dipping nets in a solution of a pyrethroid insecticide transforms the net from a simple physical barrier into a physical and chemical barrier that can repel or kill the female Anopheles mosquito, which is responsible for transmitting the malaria parasite. Pyrethroid insecticides are effective for up to 12 months, after which the nets must be retreated. More recently, companies have been producing long-lasting insecticidal nets (LLINs), which can retain residual insecticidal activity for three years or more.

Consistently sleeping under an ITN has been shown to decrease all-cause child mortality by 17 to 29 percent. There is also evidence that if more than 80 percent of households in an area sleep under an ITN, malaria transmission is significantly reduced, which can benefit people who do not use an ITN themselves.

PMI is expanding access to free and highly subsidized mosquito nets while also supporting the creation of a sustainable commercial market for ITNs in African countries. PMI supports the provision of free mosquito nets to those at highest risk from malaria – pregnant women and children under five – and to those who cannot afford to purchase a mosquito net. PMI also is increasing access to subsidized and highly-subsidized nets, which increases demand, availability, and affordability of these nets among vulnerable populations.

In just a year of implementation (December 2005 – December 2006), PMI has delivered more than one million insecticide-treated nets. This includes the distribution of free LLINs to children and pregnant women in camps for internally displaced persons in Uganda and through voucher programs, as in Tanzania where, in partnership with the Global Fund to Fight AIDS, Tuberculosis and Malaria, pregnant women and mothers of infants get a voucher that they can use at participating retailer outlets to receive a mosquito net.

PMI has partnered with UNICEF and others to deliver nets as part of an integrated national child health campaign in Angola that included measles vaccinations, vitamin A supplements, and de-worming medication. This strategy of combining ITN distribution with measles vaccinations and other health interventions was piloted two years ago. About 800,000 LLINs (420,000 of which were provided by PMI) were distributed across seven provinces where malaria transmission rates are highest in Angola.

In Uganda, an insecticide re-treatment program for 505,000 nets is helping to protect residents from malaria in 28 districts. Mosquito nets are being treated with insecticides in a plastic bag by a trained dipper in a village, allowing a large number of nets to be treated. Re-treating nets is an essential interim strategy to continue to provide protection against malaria for owners of traditional nets until existing nets are replaced with LLINs.

the insecticide spirotetramat

2009-02-25T20:33:00.000-08:00

Ecotoxicological profile of the insecticide spirotetramat

The ecotoxicological profile of the insecticide Movento® with its active ingredient spirotetramat was investigated by testing representative species of a broad variety of taxonomic groups that may be exposed to spirotetramat or its metabolites after application of the product.

Spirotetramat is of low acute and shortterm toxicity to birds and mammals. There were no adverse effects in a quail reproduction study up to high doses, but the endpoint of a duck reproduction study was significantly lower. However, there is no unacceptable chronic risk for birds when more realistic exposure conditions are considered. There is no undue chronic risk to mammals and no potential of bioaccumulation of the compound. The metabolites also pose no environmental risk to birds and mammals.

Aquatic organisms are of low sensitivity to spirotetramat in terms of acute as well as of chronic toxicity. The most sensitive aquatic organisms are chironomid midges; however, even here toxicity is low enough so that risk mitigation measures are not required for most uses to protect aquatic habitats. All relevant metabolites of spirotetramat are of low to negligible toxicity to aquatic organisms.

Spirotetramat shows no acute toxicity to honeybees. An intrinsic potential to cause brood effects was seen in lower-tier studies under unrealistic exposure conditions. Under more realistic conditions no adverse effects to the bee brood were observed in higher-tier trials.

Predatory mites are the most sensitive terrestrial arthropods. But under realistic exposure conditions even in-crop populations either suffer no significant adverse effects after applications of spirotetramat or they recover within the growing season. For off-crop populations no adverse effects are to be expected.

Soil organisms like earthworms, soil mites and soil micro-organisms were found to be of low sensitivity or insensitive to spirotetramat and its metabolites. Although there is an intrinsic potential of spirotetramat to cause phytotoxic effects, in particular to monocotyledonous plants, it was shown in higher-tier studies that non-target terrestrial plants in offcrop habitats are not at risk of adverse effects.

In conclusion, Spirotetramat exhibits a very favourable ecotoxicological profile and, when used as recommended, there is no unacceptable risk to ecosystems and to non-target organisms.