Tropical Health Matters

The use of petroleum products (PPs) such as kerosene, gasoline and engine oil to control mosquito breeding and malaria dates back to early in the last century. Generally today there is not much emphasis on larviciding measures in major control programs, let alone the use of PPs.

Therefore it was interesting to read an article by Djouaka et al. documenting the continued application of petroleum products to standing water in several villages in Benin Republic. The practice appears to have been handed down from parents to children. The authors then tested various products and found that, “The relatively high efficacy of kerosene, engine oil and waste oil is likely to be due to their elevated persistency in breeding sites after treatment.”

Beales and Gilles in the Fourth Edition of Essential Malariology devote two pages to explaining the use of “petroleum oils” on standing water surfaces and how these can be highly toxic to larvae and pupae. They also address the drawbacks including cost, problems of vegetation, debris and wind and of course environmental contamination. No examples of actual use in current malaria control programs are given.

To buttress this lack of emphasis on PPs, the recent article by van den Berg and Takken did not include these products in their “framework for decision-making in integrated vector management.” Even a 1982 WHO manual on environmental management of mosquitoes only gives a historical perspective of PPs: “The earliest chemical control of mosquitoes was directed against the larval stage. By the end of the last (19^th) century the first larviciding technique was developed. Crude kerosene and distilled petroleum oils were applied to mosquito breeding sites.”

A hint that PPs were not totally forgotten was found in a WHO 2005 Darfur Weekly Report of August 14-20, where, in the flood-affected Ardamata IDP camp, “Larval control … is accomplished by spreading used engine oil on mosquito breeding places.”

Finally in 2002 Yapabandara and Curtis reported testing various methods to control mosquito breeding in gem puts in Sri Lanka using polystyrene beads, temephos, used engine oil and filling pits with soil as well as two concentrations of pyriproxyfen. The latter chemical proved most effective and convenient needing only two applications annually while engine oil required 12 annual applications. PPs ultimately do not appear to have much to recommend them.

So let us return to the persistence of PP use in Benin communities, which occurs, Djouaka et al. surmise, because these measures are available, cheap and convenient. The ‘history’ lesson here is not a desire to return to the use of PPs, but the need for cheap and convenient malaria control measures that communities can manage for themselves.

A recent WHO publication, Preventing Disease through Health Environments, addresses environmental factors responsible for malaria spread and control. Malaria contributed 10% to the environmental burden of disease for children aged 0-14 years worldwide. Specifically, “An estimated 42% of the global malaria burden, or half a million deaths annually, could be prevented by environmental management.” According to the document, There are three main approaches to the environmental management of malaria:

• Modify the environment. This approach aims to permanently change land, water or vegetation conditions, so as to reduce vector habitats.
• Manipulate the environment. This approach temporarily produces unfavourable conditions for vector propagation and therefore needs to be repeated.
• Modify or manipulate human habitation or behaviour. This approach aims to reduce contact between humans and vectors

Although some elements of individual and household behavior are involved in environmental control, it would be be an exercise in victim blaming to assume that individuals and households can take the main responsibility for taking environment measures. Water supply, drainage, road construction, river and stream control and other environmental measures are the responsibility of institutions and governments. Unfortunately such infrastructural improvements are costly, and one does not see them addressed in major malaria control programs like GFATM and PMI.

The World Bank has noted that, “Malaria affects millions in the East Asia and Pacific (EAP) region and impedes economic development, particularly affecting the rural poor. In the early 1900s malaria was controlled in many parts of the region using environmental management (EM) for vector control. EM is where the environment is modified or manipulated to reduce malaria transmission by attacking local vector mosquitoes and requires an understanding of the ecology of these species. Today malaria control is based on drugs and insecticides…” Because of questions of sustainability and resistance, the possibility of a return to environmental management is raised.

The World Bank’s Malaria Booster Program document does consider some elements of environmental management, but many of these fall more in line with integrated vector control measures in country examples like IRS, larviciding, and larvivorous fish. Some mention is made of filling spots of standing water. The larger infrastructural issues are not addressed. This is not to say that wider World Bank projects don’t address such issues, but what is needed is a more integrated approach that the malaria control potential of infrastructural projects is assessed and planned. Other development partners need to join in this effort.