Development and evaluation of mosquito-electrocuting traps as alternatives to the human landing catch technique for sampling host-seeking malaria vectors

Abstract

BackgroundThe human landing catch (HLC) is the gold standard method for sampling host-seeking malaria vectors. However, the HLC is ethically questionable because it requires exposure of humans to potentially infectious mosquito bites.MethodsTwo exposure-free methods for sampling host-seeking mosquitoes were evaluated using electrocuting surfaces as potential replacements for HLC: (1) a previously evaluated, commercially available electrocuting grid (CA-EG) designed for killing flies, and (2) a custom-made mosquito electrocuting trap (MET) designed to kill African malaria vectors. The MET and the CA-EG were evaluated relative to the HLC in a Latin Square experiment conducted in the Kilombero Valley, Tanzania. The sampling consistency of the traps across the night and at varying mosquito densities was investigated. Estimates of the proportion of mosquitoes caught indoors (Pi), proportion of human exposure occurring indoors (πi), and proportion of mosquitoes caught when most people are likely to be indoors (Pfl) were compared for all traps.ResultsWhereas the CA-EG performed poorly (<10 % of catch of HLC), sampling efficiency of the MET for sampling Anopheles funestuss.l. was indistinguishable from HLC indoors and outdoors. For Anopheles gambiae s.l., sampling sensitivity of MET was 20.9 % (95 % CI 10.3–42.2) indoors and 58.5 % (95 % CI 32.2–106.2) outdoors relative to HLC. There was no evidence of density-dependent sampling by the MET or CA-EG. Similar estimates of Pi were obtained for An. gambiaes.l. and An. funestus s.l. from all trapping methods. The proportion of mosquitoes caught when people are usually indoors (Pfl) was underestimated by the CA-EG and MET for An. gambiae s.l., but similar to the HLC for An. funestus. Estimates of the proportion of human exposure occurring indoors (πi) obtained from the CA-EG and MET were similar to the HLC for An. gambiae s.l., but overestimated for An. funestus.ConclusionsThe MET showed promise as an outdoor sampling tool for malaria vectors where it achieved >50 % sampling sensitivity relative to the HLC. The CA-EG had poor sampling sensitivity outdoors and inside. With further modification, the MET could provide an efficient and safer alternative to the HLC for the surveillance of mosquito vectors outdoors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-1025-4) contains supplementary material, which is available to authorized users.

Comparison of two adult mosquito sampling methods with human landing catches in south-central Ethiopia

“…For African malaria vectors, the main alternative mosquito sampling methods include the standard Centers for Disease Control and Prevention light trap catches (LTC) placed beside human-occupied bed nets [2, 4, 9–11], bed net traps [12, 13], tent traps [3, 14–17], odour-baited traps [18, 19] and electrocution traps [20, 21]. …”

Erratum to: Development and evaluation of mosquito-electrocuting traps as alternatives to the human landing catch technique for sampling host-seeking malaria vectors

“…The authors regret that the statistical analysis methods used in this article [1] to assess density-dependence between different types of trap (described in the third paragraph of the Statistical analysis section and in Supplementary Information S1) are invalid. However, re-analysis with a corrected method, described below, produced similar results to those obtained using the invalid method.…”

“…The simple solution of applying the same method to untransformed counts would not be valid due to violation of the standard assumptions of linear regression (normality and homoscedasticity of residuals), on which the method relies. We have therefore developed a new method for assessing density-dependence on the untransformed count scale, described fully in [2], which we have used to re-analyse the data in [1]. Briefly, the new method models density-dependence between two trapping methods as a power law relationship, with E( x i ) =  α E( y i ) β , where x i and y i are the i th of n paired mosquito catches from traps of types X and Y, E( x i ) and E( y i ) are the expected counts of x i and y i , and α is a scaling constant.…”

“…and An. funestus s.l., collected indoors and outdoors (data from [1]). The β estimates and CIs replace the density-dependence results in Table 3 of [1], which were calculated using the invalid method.…”

“…funestus s.l., collected indoors and outdoors (data from [1]). The β estimates and CIs replace the density-dependence results in Table 3 of [1], which were calculated using the invalid method. The new results are similar to the original results, in that none of the comparisons show evidence for density dependence, with all of the 95 % CIs including the null value of one.…”