Lippia javanica (Burm F) Spreng: its general constituents and bioactivity on mosquitoes.

Mosquito repellent plants are used in the rural areas of Zimbabwe despite the fact that very few of them have been biologically evaluated. Leaves of the plant Lippia javanica, were collected from Mumurwi village, Zimbabwe and evaluated for repellency against laboratory reared Aedes aegypti mosquitoes. Major plant compounds were identified using Thin Layer Chromatography (TLC) and Mass Spectrometry (MS). Fraction 'A' contained coumarins, flavonoids and essential oils and offered a protection time of 8 and 5.5hrs in choice and non-choice experiments respectively. Fraction 'B1' contained flavonoids with a protection time of 1 and 0.5hrs in choice and non choice experiments respectively. Fraction 'B2' contained coumarins and essential oils and offered a protection time of 2hrs in either test. No major compounds were identified from the following fractions: 'C1', 'C2', 'D1', 'E1', 'E2', 'F1' and 'F2' and all of them failed to give 100% repellence. The 'C1' supernatant fraction contained coumarins and provided protection from mosquito bites for 1 and 0.5 hrs in choice and non-choice experiments respectively. Fraction 'C2' did not have the major compounds but gave a protection time of 1 hr in either experiment. Fraction 'D2' contained essential oils only and it provided a protection time of 2.5hrs in choice experiments. Analysis by MS showed the presence of alpha pinene, 1,3-5 cycloheptatriene, beta phellandrene, (+)-2-carene, 3-carene, eucalyptol and caryophyllene oxide. L. javanica offered protection from mosquito bites for 8hrs (choice) and 5.5hrs (non choice experiments). The combined presence of coumarins, flavonoids and essential oils have an additive effect compared with individual plant fractions.

The efficacy and residual life span of two alphacypermethrin insecticide formulations (Fendona 6% suspension concentrate and Fendona Dry 15%) treated on mosquito bed nets.

OBJECTIVE: To compare the effects of mosquito nets treated with two formulations of alpha-cypermethrin insecticide with a view to recommending the most appropriate formulation for use to treat mosquito nets. DESIGN: Assessment of insecticide potency under conditions of ordinary use. SETTING: Chilonga rural irrigation community in south east Lowveld Zimbabwe, a holoendemic area of year round malaria transmission. SUBJECTS: Convenience sample of 20 household heads (volunteers) was issued with treated mosquito nets. INTERVENTION: Following mosquito net treatment and distribution, bioassay tests were carried out monthly for a period of six months on insecticide and placebo treated nets. Questionnaires were administered once, one month post treatment of nets. MAIN OUTCOME MEASURES: Median mosquito knock down times of mosquitoes exposed to insecticide treated nets and community attitude towards the use of insecticide treated nets. RESULTS: Average time taken to knock down the median mosquito progressed from 2.3 minutes to 13.0 minutes for Fendona Dry 15% and from 4.1 minutes to 7.8 minutes for Fendona 6% SC over the six month period. The average time taken to knock down the median mosquito three months post-washing were 13.0 minutes and 7.4 minutes for Fendona Dry 15% and Fendona 6% SC respectively as against more than 30 minutes in controls. Both insecticides exhibited some wash resistance properties. The side effects reported were sneezing, itching, skin rash and smelling. Questionnaire data suggested that alphacypermethrin treated mosquito nets were welcomed. CONCLUSIONS: Both insecticide formulations proved to be suitable candidates. This was because of their insecticidal potency, wash resistance properties and acceptance by the community.