Illness and Diseases

The mean knockdown and mortalities of mosquitoes exposed on nets after repeated washing using two local methods: hand rubbing and beating on rocks are presented in. In general, it was observed that nets washed by machine recorded higher knockdown after one hour post exposure and 24-hour mortality respectively compared to nets washed by the other two local washing methods. The knockdown after 20 machine washes was 8%, 68%, 50% and 15% for Olyset, PermaNet, BASF and TNT respectively. The same trend was observed for mortality rates after 24 hrs post exposure. Nets washed by local methods were less effective in killing mosquitoes compared to nets washed by machine. For example, the observed mortalities were: Olyset 1% when nets were washed by beating on rocks compared to 5% when washed by machine, PermaNet recorded 44% compared to 70%, BASF recorded 13% compared to 60 and TNT, 13% compared to 30%. The mortalities for three washing methods was also analysed for each net type with machine wash as the reference using probit regression analysis. Results of modelling for mosquito mortality for Olyset when washed on rocks and machine were statistically insignificant (p > 0.05). However, a significant difference was observed between hand and machine wash p < 0.0001 for the same net type. For PermaNet, hand wash performed better in killing mosquitoes than machine wash (p < 0.0001), while machine performed better than beating on rocks (p < 0.0002). When mortality of mosquitoes was modeled for BASF, machine washing was better than hand washing (p < 0.0001), while for the same net type there was no significant difference between rock and machine (p = 0.0703). Finally, for TNT results of machine and washing by hand were statistically insignificant, but the results of washing same net by rock and machine were significantly different p < 0.0001. Mexican pharmacy prices
Discussion
The current study found that the effectiveness and biodurability of LLINs is influenced by washing methods and drying regimen that are used in the field. Overall, nets that were washed and dried hanging under the shade significantly retained more insecticide and were more effective compared to nets that were washed and dried using other regimens. Generally nets that were dried spread on the ground in direct sunlight lost the most amount of insecticide and were least effective. This finding suggests that contact between wet nets and the ground seem to facilitate transfer of insecticide from netting to the ground or to other surfaces. Unfortunately this is the most preferred method of drying nets in local villages where they are used for malaria vector contro1. The study also found that nets that were washed by the standard WHOPES washing protocol retained more insecticide and were generally more effective in killing mosquitoes than nets that were washed using a local method of beating on rocks. Among the factors that affect efficacy of LLINs, washing seem to be the most important and widely studied. In the current study, it was observed that generally, washing of LLINs gradually removed insecticides on all the four brands of that were evaluated regardless of washing method used. However, the rate at which the insecticide loss occurred was not uniform. It varied by washing method used, (abrasiveness) and the net type (brand).