An improved mosquito electrocuting trap that safely reproduces epidemiologically relevant metrics of mosquito human-feeding behaviours as determined by human landing catch.
BACKGROUND
Reliable quantification of mosquito host-seeking behaviours is required to determine the efficacy of vector control methods. For malaria, the gold standard approach remains the risky human landing catch (HLC). Here compare the performance of an improved prototype of the mosquito electrocuting grid trap (MET) as a safer alternative with HLC for measuring malaria vector behaviour in Dar es Salaam, Tanzania.


METHODS
Mosquito trapping was conducted at three sites within Dar es Salaam representing a range of urbanicity over a 7-month period (December 2012-July 2013, 168 sampling nights). At each site, sampling was conducted in a block of four houses, with two houses being allocated to HLC and the other to MET on each night of study. Sampling was conducted both indoors and outdoors (from 19:00 to 06:00 each night) at all houses, with trapping method (HLC and MET) being exchanged between pairs of houses at each site using a crossover design.


RESULTS
The MET caught significantly more Anopheles gambiae sensu lato than the HLC, both indoors (RR [95 % confidence interval (CI)]) = 1.47 [1.23-1.76], P < 0.0001 and outdoors = 1.38 [1.14-1.67], P < 0.0001). The sensitivity of MET compared with HLC did not detectably change over the course of night for either An. gambiae s.l. (OR [CI]) = 1.01 [0.94-1.02], P = 0.27) or Culex spp. (OR [CI]) = 0.99 [0.99-1.0], P = 0.17) indoors and declined only slightly outdoors: An. gambiae s.l. (OR [CI]) = 0.92 [0.86-0.99], P = 0.04), and Culex spp. (OR [CI]) = 0.99 [0.98-0.99], P = 0.03). MET-based estimates of the proportions of mosquitoes caught indoors (P i ) or during sleeping hours (P fl ), as well as the proportion of human exposure to bites that would otherwise occurs indoors (π i ), were statistically indistinguishable from those based on HLC for An. gambiae s.l. (P = 0.43, 0.07 and 0.48, respectively) and Culex spp. (P = 0.76, 0.24 and 0.55, respectively).


CONCLUSIONS
This improved MET prototype is highly sensitive tool that accurately quantifies epidemiologically-relevant metrics of mosquito biting densities, behaviours and human exposure distribution.
Environmental Health and Ecological Sciences Thematic Group, Coordination Office, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania. govella@ihi.or.tz.
Nicodem J
NJ
Govella
Environmental Health and Ecological Sciences Thematic Group, Coordination Office, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania.|College of Medical, Veterinary and Life Sciences, Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow, UK.
Deodatus F
DF
Maliti
Environmental Health and Ecological Sciences Thematic Group, Coordination Office, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania.
Amos T
AT
Mlwale
Environmental Health and Ecological Sciences Thematic Group, Coordination Office, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania.
John P
JP
Masallu
Bioelectronics Unit, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK.
Nosrat
N
Mirzai
College of Medical, Veterinary and Life Sciences, Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow, UK.
Paul C D
PC
Johnson
College of Medical, Veterinary and Life Sciences, Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow, UK.
Heather M
HM
Ferguson
Environmental Health and Ecological Sciences Thematic Group, Coordination Office, Ifakara Health Institute, PO Box 78373, Kiko Avenue, Mikocheni, Dar es Salaam, United Republic of Tanzania.|Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
Gerry F
GF
Killeen
D000328:Adult; D000818:Animals; D000852:Anopheles / Q000502:physiology*; D018592:Cross-Over Studies; D003465:Culex / Q000502:physiology*; D004560:Electricity; D004772:Entomology / Q000379:methods*; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D013636:Tanzania; D014838:Volunteers
Africa; Anopheles gambiae; Behaviour; Culex; Exposure-free; Malaria vector; Mosquito; TRAPS