People's perceptions about malaria transmission and control using mosquito repellent plants in a locality in Zimbabwe.

OBJECTIVE: To assess peoples' perceptions and knowledge about malaria transmission and control with special reference to the use of plants as mosquito repellents. DESIGN: Cross sectional study. SETTING: Mandeya ward "A" (33 degrees E and 18 degrees 30' S), Honde Valley, Zimbabwe. SUBJECTS: 226 household heads present when interview was conducted. MAIN OUTCOME MEASURES: Mosquito control methods, spraying coverage, plants used to repel mosquitoes and reasons for using them. RESULTS: 215 (95.0%) of the respondents' homes had been sprayed and their understanding of malaria transmission was not related to compliance with the National Malaria Control Programme (NMCP). Taking mosquito control measures was related to knowledge of malaria transmission, with 24 (75.0%) of those who did not know, taking no measures of their own. The use of plants was mentioned by 50 (23.5%) of the respondents and the reasons given were that they were cheap 43 (86.0%), effective five (10.0%) and locally available two (4.0%). The plant which was mentioned as being used by all age groups was L. javanica 25 (50.0%) and the other plants were used to a lesser extent. Forty six (92.0%) of the people said that they had used plants for mosquito control. The leafy part of the plant was used by 43 (86.0%) and a fresh preparation 43 (86.2%) gave better protection than a dry one. The plants were crushed and applied on the skin by eight people (14.6%), burnt by 36 people (72.8%) and used in their original form by six people (12.6%) and used once per by day 42 people (84.0%). CONCLUSIONS: One of the important points to emerge from this study is that, despite widespread knowledge about the morbidity of malaria, understanding about its prevention was generally low and this has negative implications on an integrated control programme.

Efficacy of mosquito coils containing 0.3% and 0.4% pyrethrins against An.gambiae sensu lato mosquitoes.

OBJECTIVE: To investigate the efficacy of a formulation containing 0.4% pyrethrins against registered mosquito coil containing 0.3% pyrethrins. DESIGN: Non intervention analytical study. SETTING: Four villages in Mashonaland East province, Mumurwi, Chitengu, Katiyo and Nyagande. SUBJECTS: Biological efficacy of Doom and IT mosquito coils. MAIN OUTCOME MEASURES: To measure insecticidal, knock down and inhibition of biting activities of the coils in the presence of mosquitoes. RESULTS: A two hour exposure of mosquitoes to both coils results in a 99% and 98.5% mortality rate for a 0.4% and a 0.3% formulation respectively. The KT50 and KT90 of a formulation containing 0.4% pyrethrins were half those of a 0.3% formulation, suggesting that a 0.4% formulation has a rapid knock down effect. A formulation containing 0.4% pyrethrins inhibited 92.5% from biting as compared to a 0.3% formulation (80%). CONCLUSION: A formulation containing 0.4% pyrethrins is more effective in repelling mosquitoes than a 0.3% formulation.

Biological activity of permethrin, phenothrin/allerthrin and D-phenothrin on Periplaneta americana and Blattella germanica cockroaches.

The biological activity of permethrin, phenothrin/allethrin and d-phenothrin was evaluated against Periplaneta americana and Blattella germanica cockroaches. A decrease in the number of cockroaches caught after spraying the trial huts was observed. The decrease may be attributed to either the presence of trap-weary specimens or because P. americana is not fully attracted by left over food. One hundred percent knock down was achieved after 10 minutes for all insecticides. The knock down rates for d-phenothrin and permethrin were similar as compared to a combination of phenothrin/allethrin. However, all insecticides were not very effective against cockroaches because the field residual effect was from one day to two days.

Do traditional mosquito repellent plants work as mosquito larvicides?

Plant derived larvicides were evaluated in Kamhororo, an area of Zimbabwe. Twenty five third and fourth instar An. gambiae s.s mosquito larvae were used per test according to the method of WHO. All larvicides were effective against the An. gambiae s.s mosquito larvae and were comparable to studies done in Tanzania using Orange peel extracts. The extracts of the plant Ocimum canum (LC50 = 54, 94 x 10(3) ug/ml) were more effective in killing the larvae than Lippia javanica (LC50 = 125,34mg x 10(3) ug/ml). These concentrations are higher when considering commercial larvicides.

Do mosquito coils and killer sticks work against Anopheles gambiae sensu lato mosquitoes in Zimbabwe?

Tests against Anopheles gambiae s. 1. mosquitoes (malaria transmitting mosquitoes) were carried out in Chegutu, Chiredzi and Kamhororo (Gokwe). These tests were done in relatively closed rural huts and experimental huts. The tests demonstrated that a one hour exposure to smoke from the burning of insecticidal coils contain 0.3 pc pyrethrin, achieve 100 pc knockdown of mosquitoes. Mosquito killer sticks gave 85 pc knockdowns with 30 pc recoveries and less than 10 pc recoveries for the coils. With caged insects in Gokwe the KD50 for both the coils and sticks was been 15 to 20 minutes and the KD90 ranged from 40 to 50 minutes. The coils were observed to more lethal than the sticks. Mortalities were 100 pc for the coils and 85 pc for the killer sticks after a 24 hour holding period.