The field evaluation of a push-pull system to control malaria vectors in northern Belize, Central America.
BACKGROUND
Campaigns for the continued reduction and eventual elimination of malaria may benefit from new and innovative vector control tools. One novel approach being considered uses a push-pull strategy, whereby spatial repellents are used in combination with outdoor baited traps. The desired effect is the behavioural manipulation of mosquito populations to elicit movement of vectors away from people and into traps.


METHODS
Here, a prototype push-pull intervention was evaluated using an experimental hut methodology to test proof-of-principle for the strategy against two natural vector populations, Anopheles albimanus and Anopheles vestitipennis, in Belize, Central America. A Latin square study design was used to compare mosquito entry into experimental huts and outdoor traps across four different experimental conditions: 1) control, with no interventions; 2) pull, utilizing only outdoor traps; 3) push, utilizing only an indoor spatial repellent; and 4) push-pull, utilizing both interventions simultaneously.


RESULTS
For An. vestitipennis, the combined use of an indoor repellent and outdoor baited traps reduced average nightly mosquito hut entry by 39% (95% CI: [0.37-0.41]) as compared to control and simultaneously increased the nightly average densities of An. vestitipennis captured in outdoor baited traps by 48% (95% CI: [0.22-0.74]), compared to when no repellent was used. Against An. albimanus, the combined push-pull treatment similarly reduced hut entry, by 54% (95% CI: [0.40-0.68]) as compared to control; however, the presence of a repellent indoors did not affect overall outdoor trap catch densities for this species. Against both anopheline species, the combined intervention did not further reduce mosquito hut entry compared to the use of repellent alone.


CONCLUSIONS
The prototype intervention evaluated here clearly demonstrated that push-pull strategies have potential to reduce human-vector interactions inside homes by reducing mosquito entry, and highlighted the possibility for the strategy to simultaneously decrease human-vector interactions outside of homes by increasing baited trap collections. However, the variation in effect on different vectors demonstrates the need to characterize the underlying behavioral ecology of target mosquitoes in order to drive local optimization of the intervention.
Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD, 20814, USA. joseph.m.wagman@gmail.com.
Joseph M
JM
Wagman
College of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Galvin Life Sciences Center, Notre Dame, IN, 46556, USA. jgrieco@nd.edu.
John P
JP
Grieco
Ministry of Health, East Block Independence Plaza, Belmopan, Belize. kbautista@health.gov.bz.
Kim
K
Bautista
Ministry of Health, East Block Independence Plaza, Belmopan, Belize. mohpolanco@yahoo.com.
Jorge
J
Polanco
Ministry of Health, East Block Independence Plaza, Belmopan, Belize. jowagman@yahoo.com.
Ireneo
I
Briceño
Ministry of Health, East Block Independence Plaza, Belmopan, Belize. russellking35@gmail.com.
Russell
R
King
College of Biological Sciences, Eck Institute for Global Health, University of Notre Dame, Galvin Life Sciences Center, Notre Dame, IN, 46556, USA. nachee@nd.edu.
Nicole L
NL
Achee
D000818:Animals; D000852:Anopheles; D001531:Belize; D005260:Female; D006801:Humans; D007302:Insect Repellents; D007303:Insect Vectors; D008288:Malaria / Q000517:prevention & control* / Q000635:transmission; D009032:Mosquito Control / Q000379:methods*
D007302:Insect Repellents