Comparative Field Evaluation of the Mbita Trap, the Centers for Disease Control Light Trap, and the Human Landing Catch for Sampling of Malaria Vectors in Western Kenya

Abstract

The mosquito sampling efficiency of a new bed net trap (the Mbita trap) was compared with that of the Centers for Disease Control miniature light trap (hung adjacent to an occupied bed net) and the human landing catch in western Kenya. Overall, the Mbita trap caught 48.7 +/- 4.8% (mean +/- SEM) the number of Anopheles gambiae Giles sensu lato caught in the human landing catch and 27.4 +/- 8.2% of the number caught by the light trap. The corresponding figures for Anopheles funestus Giles were 74.6 +/- 1.3% and 39.2 +/- 1.9%, respectively. Despite the clear differences in the numbers of mosquitoes caught by each method, both the Mbita trap and light trap catches were directly proportional to human landing catches regardless of mosquito density. No significant differences in parity or sporozoite incidence were observed between mosquitoes caught by the three methods for either An. gambiae s.l. or An. funestus. Identification of the sibling species of the An. gambiae complex by a polymerase chain reaction indicated that the ratio of An. gambiae Giles sensu stricto to An. arabiensis Patton did not vary according to the sampling method used. It is concluded that the Mbita trap is a promising tool for sampling malaria vector populations since its catch can be readily converted into equivalent human biting catch, it can be applied more intensively, it requires neither expensive equipment nor skilled personnel, and it samples mosquitoes in an exposure-free manner. Such intensive sampling capability will allow cost-effective surveillance of malaria transmission at much finer spatial and temporal resolution than has been previously possible.

Light traps fail to estimate reliable malaria mosquito biting rates on Bioko Island, Equatorial Guinea

“…The conversion factors for Arena Blanca and Riaba, although calculated from outdoor collections, are among the lowest reported in Africa [9-13,15-18] and approach the extremely low light trap collection efficiency (LTC:HLC = 0.02) found in urban Dar es Salaam, Tanzania [19]. The authors of that study suggested that the poor light trap performance was affected by the city lights and concluded that light traps are not appropriate for mosquito surveillance and monitoring the impact of mosquito control measures in Dar es Salaam [19].…”

“…Several studies have compared various types of human-baited tent trap designs with LTCs and HLCs for estimating relative sampling efficiencies [15-19]. These studies also report widely varying 1:1 LTC:HLC relative sampling efficiencies; 0.02 in urban Dar es Salaam, Tanzania [19]; 0.33 in the Kilombero valley, Tanzania [17]; 0.56 in Ahero, western Kenya [16]; 1.3 also in Kilombero, Tanzania [18]; and 1.86 in Lwanda, western Kenya [15].…”

“…These studies also report widely varying 1:1 LTC:HLC relative sampling efficiencies; 0.02 in urban Dar es Salaam, Tanzania [19]; 0.33 in the Kilombero valley, Tanzania [17]; 0.56 in Ahero, western Kenya [16]; 1.3 also in Kilombero, Tanzania [18]; and 1.86 in Lwanda, western Kenya [15]. It was suggested that the extremely low efficiency of light traps in Dar es Salaam was caused by the highly illuminated, urban environment reducing the efficacy of the light source in the traps [19].…”

A quantitative analysis of transmission efficiency versus intensity for malaria

“…The difference between the EIR and the FOI has been measured, rediscovered and discussed several times 12,14,17,19,20 Bias in estimating the EIR could explain some of the pattern; several common methods of estimating the EIR are known to be biased relative to one another 39,40 . A bias in EIR could explain why the highest transmission efficiency in Saradidi was approximately half of that observed for experimental challenge to infectious mosquitoes.…”

Rapid assessment of malaria risk using entomological techniques: taking an epidemiological snapshot

“…Mosquitoes possibly represent the most captured insect group in the world, and many methods to catch them have been devised (Figure 5), from which several can be selected that best answer the specific questions. For example, if the aim is to determine spatial variations in the EIR, then adult mosquitoes from light traps, tent or bednet traps (Mathenge et al 2002;2004), or landing or resting catches will suffice. If parasitaemias or human to mosquito transmission are of interest then mosquitoes with blood meals need to be collected.…”