Insecticide space spraying for preventing malaria transmission

What is space spraying and how might it work?

Space spraying is the outdoor spraying of insecticides to kill adult insects. The insecticide is dispersed using hand‐held, vehicle‐mounted or aircraft‐mounted equipment to produce a fog. Space spraying is regularly used in public health and pest control programmes, including use as an emergency response to malaria epidemics. Insecticide‐treated bed nets and indoor spraying of insecticides are the two interventions most commonly used by malaria programmes to control mosquito populations. Both interventions are effective at reducing human contact with indoor‐biting mosquito species. If successful, space spraying reduces populations of outdoor‐biting mosquitoes, and may help reduce malaria transmission from the mosquito species least affected by typical control efforts. At present, however, there remains widespread uncertainty over whether space spraying has any impact on malaria transmission.

What is the aim of the review?

In order to guide decision‐making for malaria control programmes, the aim of this Cochrane Review was to summarize the actions taken and reported findings of trials evaluating the impact of space spraying on malaria transmission.

What are the main findings of the review?

After searching for relevant trials up to 18 April 2018, we identified four studies conducted between 1972 and 2000. Across the four studies, a range of insecticide delivery methods were used, including handheld, vehicle‐mounted, and aircraft‐mounted spraying equipment. A variety of different insecticides, doses, and spraying times were also used to suit the local environment and the behaviour of the targeted mosquito species.

In three studies, the evidence was considered to be unsuitable for reliably assessing the impact of space spraying on the number of cases of malaria. The remaining study, which took place in a single state in India and covered a combined population of 18,460 people, reported the number of malaria cases in the years preceding and following the introduction of space spraying. The evidence suggested that space spraying led to a decrease in the number of cases of malaria, but as the trial was conducted over 30 years ago and within one state in India, we cannot be certain that these findings are applicable in other areas where malaria occurs. Reliable research in a variety of settings will help to establish whether and when this intervention may be worthwhile.