A systematic, realist review of zooprophylaxis for malaria control.
BACKGROUND
Integrated vector management (IVM) is recommended as a sustainable approach to malaria control. IVM consists of combining vector control methods based on scientific evidence to maximize efficacy and cost-effectiveness while minimizing negative impacts, such as insecticide resistance and environmental damage. Zooprophylaxis has been identified as a possible component of IVM as livestock may draw mosquitoes away from humans, decreasing human-vector contact and malaria transmission. It is possible, however, that livestock may actually draw mosquitoes to humans, increasing malaria transmission (zoopotentiation). The goal of this paper is to take a realist approach to a systematic review of peer-reviewed literature to understand the contexts under which zooprophylaxis or zoopotentiation occur.


METHODS
Three electronic databases were searched using the keywords 'zooprophylaxis' and 'zoopotentiation', and forward and backward citation tracking employed, to identify relevant articles. Only empirical, peer-reviewed articles were included. Critical appraisal was applied to articles retained for full review.


RESULTS
Twenty empirical studies met inclusion criteria after critical appraisal. A range of experimental and observational study designs were reported. Outcome measures included human malaria infection and mosquito feeding behaviour. Two key factors were consistently associated with zooprophylaxis and zoopotentiation: the characteristics of the local mosquito vector, and the location of livestock relative to human sleeping quarters. These associations were modified by the use of bed nets and socio-economic factors.


CONCLUSIONS
This review suggests that malaria risk is reduced (zooprophylaxis) in areas where predominant mosquito species do not prefer human hosts, where livestock are kept at a distance from human sleeping quarters at night, and where mosquito nets or other protective measures are used. Zoopotentiation occurs where livestock are housed within or near human sleeping quarters at night and where mosquito species prefer human hosts.


CONCLUSIONS
The evidence suggests that zooprophylaxis could be part of an effective strategy to reduce malaria transmission under specific ecological and geographical conditions. The current scientific evidence base is inconclusive on understanding the role of socio-economic factors, optimal distance between livestock and human sleeping quarters, and the effect of animal species and number on zooprophylaxis.
Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC, H3A 0B9, Canada. blanaid.donnelly@mail.mcgill.ca.
Blánaid
B
Donnelly
Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC, H3A 0B9, Canada. lea.berrangford@mcgill.ca.
Lea
L
Berrang-Ford
Department of Geography, McGill University, Burnside Hall Building, 805 Sherbrooke St West, Montreal, QC, H3A 0B9, Canada. nancy.ross@mcgill.ca.
Nancy A
NA
Ross
Public Health Risk Sciences Division, Public Health Agency of Canada, 3200 Sicotte, PO Box 5000, Saint-Hyacinthe, QC, J2S 7C6, Canada. pascal.michel@phac-aspc.gc.ca.
Pascal
P
Michel
D000818:Animals; D000852:Anopheles / Q000502:physiology*; D006799:Housing, Animal; D006801:Humans; D007303:Insect Vectors / Q000502:physiology*; D008288:Malaria / Q000469:parasitology / Q000517:prevention & control*; D009032:Mosquito Control / Q000379:methods*; D057147:Mosquito Nets