Integrated Vector Management Bill Brieger | 04 Nov 2007 05:15 pm
Oil on (Mosquito) Troubled Waters
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.â€
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 (19th) century the first larviciding technique was developed. Crude kerosene and distilled petroleum oils were applied to mosquito breeding sites.â€
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.â€
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.