In an experiment reported in the Indian Journal of Malariology (33: 81-87), authors M.A. Ansari and R.K. Razdan describe how burning 1% neem oil in kerosene lamps from dusk to dawn resulted in the movement of the mosquito Anopheles culicifacies (a carrier of the malaria pathogen) from living rooms to cattlesheds. As a result, the incidence of malaria in experimental villages dropped significantly.
Lamps used were 100 ml capacity, with a wick and regulator. Rooms in the study were 3.5 m x 3.5 m x 3.5 m. In the experimental village, the average number of mosquitoes per room went from 64.8 to 14.06. In the control village, where plain kerosene was burned, the average density of mosquitoes dropped from 87.25 to 55.0. When lamps were taken away, the density of A. culicifacies increased again.
The authors pointed out that the degree of protection conferred by neem oil varies between different species of mosquitoes.
Before the experiment, the number of cases of malaria per 1000 people in the experimental village and the control village were similar (3.1 and 2.6, respectively). During the experiment, cases/1000 for the experimental village was 1.03, compared to 9.6 for the control village.
Plasmodium falciparum is the species of malaria that most often results in death. In villages where 1% neem oil was burned with the kerosene, no cases of P. falciparum malaria were reported. In control villages where plain kerosene was burned, data showed 4.3 cases of P. falciparum per 1000 people.
The neem oil used in the study was obtained from a pharmaceutical company. Oil produced locally would be cheaper; the authors estimate a cost of Rs. 35-50 per liter for locally produced oil. Neem oil for this use would cost Rs. 2.0 per person per year, while kerosene would cost Rs. 8.0 per room each month. The authors claim that the cost of this technique for malaria control would be cheaper than coils or impregnated mats. [DRB: We do not know what the effectiveness of this locally produced oil would be compared to oil obtained from a pharmaceutical company.]