Measuring public-health outcomes of release of transgenic mosquitoes

The transgenic RIDL method could ensure that male mosquitos can be released without biting females and that the males would have no female progeny after mating to wild females. Urban Anopheles or Aedes vector populations, surrounded by different species in rural areas, would seem to be the most appropriate targets for such releases, aiming at eradication. In urban areas intensity of transmission is generally not very high and the public-health outcomes of such urban programmes could be monitored by passive surveillance through health facilities or by active surveillance for infections with or without associated symptoms. The alternative use of transgenic mosquitos would be to produce strains refractory to infection by pathogens such as Plasmodium and to drive such genes into wild populations. In theory, in contrast to sterile-male eradication, such a procedure could "resist" a limited level of immigration and could open up the possibility of using the method against African rural malaria. However, in practice it would seem extremely difficult or impossible to ensure the necessary complete linkage of the refractoriness genes to the driving system. If this problem could be overcome one could monitor the impact of the spreading of the refractoriness genes by its impact on (i) the sporozoite rate in the wild population; (ii) the incidence of re-infection after clearing existing infections with an appropriate drug treatment; (iii) active surveillance for prevalence of malaria fever and anaemia in children; (iv) attacks of severe malaria and deaths monitored though hospitals and village reporters

Investigation of negative cross-resistance as a resistance-management tool for insecticide-treated nets.

Resistance management for insecticide-treated nets (ITNs) remains a challenge. Options are limited, because a safe and highly active insecticide with a persistence of several months is required. These criteria have only been met by pyrethroids, although organophosphates (OPs) and carbamates have been considered as alternatives for impregnation of eave curtains. It has been observed that some pyrethroid-resistant mosquito strains show increased OP susceptibility over pyrethroid-susceptible strains (i.e., negative cross-resistance). The current study investigated whether this phenomenon applies to a range of mosquito species and strains, because a mixture or rotation strategy for resistance management could then be envisaged. Adult female mosquitoes from laboratory strains of Anopheles stephensi Liston, Anopheles gambiae Giles, and Culex quinquefasciatus Say were tested in World Health Organization susceptibility test kits. For An. stephensi, the highly pyrethroid-resistant DUB 234 strain showed the same level of resistance to malathion as the pyrethroid-susceptible DUB S. The malathion-resistant ST MAL strain was as susceptible to pyrethroids as the insecticide-susceptible BEECH. For An. gambiae, the malathion tolerance of the previously pyrethroid-resistant RSP strain was significantly higher than that of the insecticide-susceptible KWA. For Cx. quinquefasciatus, selection of the QUINQ strain with permethrin abolished preexisting resistance to the OP malathion as pyrethroid resistance increased, rendering the strain more susceptible to malathion than PEL SS. Some indication of negative cross-resistance to malathion was found for the permethrin-resistant MUHEZA strain. The occurrence of negative cross-resistance seems dependent on the history of insecticide selection and is not generally applicable. Resistance management for ITNs will need to use mechanisms other than negative cross-resistance to be effective

Insecticide treated bednets: A review

The functioning and efficacy of Insecticide Treated Nets (ITNs) in controlling malaria are discussed in the present review. ITNs Insecticide Treated Nets (ITNs) have been shown to have a beneficial impact in reducing malaria mortality and morbidity in children. However, a few issues are still unresolved: for instance the short and long term effects of an artificially induced reduction in the intensity of malaria transmission on the immune system and the mortality of children is not entirely understood; further studies are needed on whether the spread of resistance to pyrethroids, which is the only class of insecticide currently recommended on nets, affects the effectiveness of ITNs so that resistance to these insecticides would constitutes a serious threat for the success of the malaria vector control programs. Lastly, the economic aspects are presented. The main problem is to find a way for a sustainable implementation of this methodology, that includes purchasing new bednets, delivery and the regular re-impregnation of the existing nets. Free delivery and retreatment in poor countries is not only more equitable but also more efficient than marketing methods

The feeding behaviour and Plasmodium infection of Anopheles mosquitoes in southern Ethiopia in relation to use of insecticide-treated livestock for malaria control.

Anopheles arabiensis and An. quadriannulatus species B mosquitoes were collected at sites of human and livestock housing and analysed for blood feeding patterns and infection with malaria sporozoites. A low percentage of human blood meals at some sites suggested that zooprophylaxis could be effective in reducing challenge from Plasmodium falciparum

Experimental hut comparisons of nets treated with carbamate or pyrethroid insecticides, washed or unwashed, against pyrethroid-resistant mosquitoes.

The efficacy against mosquitoes (Diptera: Culicidae) of a bednet treated with carbamate insecticide [carbosulfan capsule suspension (CS) 200 mg/m(2)] was compared with four types of pyrethroid-treated nets in veranda-trap huts at Yaokoffikro near Bouaké, Côte d'Ivoire, where the malaria vector Anopheles gambiae Giles carries the kdr gene (conferring pyrethroid resistance) at high frequency and Culex quinquefasciatus Say is also pyrethroid resistant. Pyrethroids compared were lambdacyhalothrin CS 18 mg/m(2), alphacypermethrin water dispersible granules (WG) 20 mg/m(2), deltamethrin 50 mg/m(2) (Permanet) and permethrin emulsifiable concentrate (EC) 500 mg/m(2). Insecticidal power and personal protection from mosquito bites were assessed before and after the nets were used for 8 months and hand washed five times in cold soapy water. Before washing, all treatments except permethrin significantly reduced blood-feeding and all had significant insecticidal activity against An. gambiae. The carbosulfan net gave significantly higher killing of An. gambiae than all pyrethroid treatments except the Permanet. Against Culex spp., carbosulfan was more insecticidal and gave a significantly better protective effect than any of the pyrethroid treatments. After washing, treated nets retained various degrees of efficacy against both mosquito genera - but least for the carbosulfan net. Washed nets with three types of pyrethroid treatment (alphacypermethrin, lambdacyhalothrin, permethrin) gave significantly higher mortality rates of Culex than in huts with the same pyrethroid-treated nets before washing. After five washes, the Permanet, which is sold as a long-lasting insecticidal product, performed no better than the other nets in our experimental conditions

High Effective Coverage of Vector Control Interventions in Children After Achieving Low Malaria Transmission in Zanzibar, Tanzania.

\ud \ud Formerly a high malaria transmission area, Zanzibar is now targeting malaria elimination. A major challenge is to avoid resurgence of malaria, the success of which includes maintaining high effective coverage of vector control interventions such as bed nets and indoor residual spraying (IRS). In this study, caretakers' continued use of preventive measures for their children is evaluated, following a sharp reduction in malaria transmission. A cross-sectional community-based survey was conducted in June 2009 in North A and Micheweni districts in Zanzibar. Households were randomly selected using two-stage cluster sampling. Interviews were conducted with 560 caretakers of under-five-year old children, who were asked about perceptions on the malaria situation, vector control, household assets, and intention for continued use of vector control as malaria burden further decreases. Effective coverage of vector control interventions for under-five children remains high, although most caretakers (65%; 363/560) did not perceive malaria as presently being a major health issue. Seventy percent (447/643) of the under-five children slept under a long-lasting insecticidal net (LLIN) and 94% (607/643) were living in houses targeted with IRS. In total, 98% (628/643) of the children were covered by at least one of the vector control interventions. Seasonal bed-net use for children was reported by 25% (125/508) of caretakers of children who used bed nets. A high proportion of caretakers (95%; 500/524) stated that they intended to continue using preventive measures for their under-five children as malaria burden further reduces. Malaria risk perceptions and different perceptions of vector control were not found to be significantly associated with LLIN effective coverage While the majority of caretakers felt that malaria had been reduced in Zanzibar, effective coverage of vector control interventions remained high. Caretakers appreciated the interventions and recognized the value of sustaining their use. Thus, sustaining high effective coverage of vector control interventions, which is crucial for reaching malaria elimination in Zanzibar, can be achieved by maintaining effective delivery of these interventions

Child feces disposal practices in rural Orissa: a cross sectional study.

BACKGROUND: An estimated 2.5 billion people worldwide lack access to improved sanitation facilities. While large-scale programs in some countries have increased latrine coverage, they sometimes fail to ensure optimal latrine use, including the safe disposal of child feces, a significant source of exposure to fecal pathogens. We undertook a cross-sectional study to explore fecal disposal practices among children in rural Orissa, India in villages where the Government of India's Total Sanitation Campaign had been implemented at least three years prior to the study. METHODS AND FINDINGS: We conducted surveys with heads of 136 households with 145 children under 5 years of age in 20 villages. We describe defecation and feces disposal practices and explore associations between safe disposal and risk factors. Respondents reported that children commonly defecated on the ground, either inside the household (57.5%) for pre-ambulatory children or around the compound (55.2%) for ambulatory children. Twenty percent of pre-ambulatory children used potties and nappies; the same percentage of ambulatory children defecated in a latrine. While 78.6% of study children came from 106 households with a latrine, less than a quarter (22.8%) reported using them for disposal of child feces. Most child feces were deposited with other household waste, both for pre-ambulatory (67.5%) and ambulatory (58.1%) children. After restricting the analysis to households owning a latrine, the use of a nappy or potty was associated with safe disposal of feces (OR 6.72, 95%CI 1.02-44.38) though due to small sample size the regression could not adjust for confounders. CONCLUSIONS: In the area surveyed, the Total Sanitation Campaign has not led to high levels of safe disposal of child feces. Further research is needed to identify the actual scope of this potential gap in programming, the health risk presented and interventions to minimize any adverse effect