Abstract:
Laboratory experiments were conducted at the National Malaria Center- Sinnar
state to investigate the effects of organic extracts of leaves and seed kernels of neem
(Azadirachta indica A.juss.), leaves of cafure (Eucalyptus camaldulensis Dehn.), and
leaves of rehan (Ocimum basilicum L.) against the larvae and adult of the main malaria
vector in Sudan Anopheles arabiensis patton.
The larvicidal activity of ethanol and hexane extracts of neem and cafure with
different concentrations were measured according to the WHO standards for testing
susceptibility of mosquito larvae to insecticides. This compared with specific
concentrations of the standard larvicide Temphos and the bacterium Bacillus
thuringirnsis var. Kurstaki, representing conventional and biological mosquito control
measures respectively. Results indicated that cafure leaves hexane extract (CLH) had the
greatest larvicidal effect with LC50 127.9 ppm, when compared to other plant extracts.
However its initial levels effects were superior to that of the standard larvicide Temphos
and Bacillus thuringiensis var. kurstaki. concentrations, when measured after 24 hours
exposure.
Neem, cafure, and rehan organic extracts (ethanol, and hexane) were tested against
Anopheles arabiensis adult by calculating repellency every 30 minutes. In addition to
oviposition deterrency and adult mortality after 24 hours exposure, when used as paper
impregnation exposed inside an excito-repellency box recommended by the WHO.
Results showed that cafure, and rahan leaves hexane extracts at the rate of 10% were the
best that could repel the adult insect for a period of time up to 2 hours. Meanwhile all
plant extracts exhibited oviposition deterrency properties, but rehan leaves hexane extract
at 1% concentration ranked first, followed by cafure leaves hexane extract with the rate
10%. However results pointed out that CLH exerted little insecticidal characteristics after
24 hours exposure towards the tested species that could be monitored and confirmed
under field conditions.
Resistance / susceptibility test was carried out using WHO kits, to update the
resistance status of Anopheles arabiensis adult to the common used insecticides DDT,
ii
malathion, and propoxure. The results demonstrated that the average mortality levels
exhibited by Anopheles. arabiensis adult to DDT, malathion, and propoxur insecticides
were below the WHO susceptibility standards. Hence constitutes the alarm that not to use
these products in the field of malaria vectors control extensively in that area.
Results concluded that plant extracts nominated in this study (CLH, RLH) could be
compatible to be applied with other conventional and biological measures in IPM
programmes used for malaria vectors control, after field verifications.
