Optimization of odour-baited resting boxes for sampling malaria vector, Anopheles arabiensis Patton, in arid and highland areas of Africa

Kweka et al. Parasites & Vectors 2010, 3:75 http://www.parasitesandvectors.com/content/3/1/75 RESEARCH Open Access Optimization of odour-baited resting boxes for sampling malaria vector, Anopheles arabiensis Patton, in arid and highland areas of Africa Eliningaya J Kweka1*, ,Beda J Mwang’onde1, Aneth M Mahande2 Abstract Background: Odour baited resting boxes are simple, reliable and important tools for sampling malaria vector mosquitoes in surveillance and control programmes in different parts of Africa. To optimize the use of cow urine baited resting boxes for sampling An. arabiensis, a community-based study was conducted in Mabogini hamlet in the Lower Moshi irrigation scheme area. Method: Experimental designs using 3 by 3 Latin square were conducted for twenty days to evaluate the following: i) the effect of different parameters in the sampling of mosquitoes using odour baited resting boxes; ii) the performance of odour baited traps under indoor and outdoor conditions and the effect of people sleeping indoors on mosquito density; iii) the effect of position in the placement of traps on collection of mosquitoes; and, iv) the efficiency of the trap outdoors at three different distances from the house wall. One extra house served as the sentinel house to monitor species abundance using a CDC-miniature light trap. Results: 8581 mosquitoes were sampled by odour baited resting boxes of which, 8051 (93.82%) were An. arabiensis and 530 (6.18%) Cx. quinquefasciatus. The light trap collected 12,420 mosquitoes, of which 9442 (76.02%) were An. arabiensis, 126 (1.01%) An. funestus group, 230 (1.85%) An. rufipes and 2622 (21.11%) Cx. quinquefasciatus. The best height for outdoor mosquitoes sampling was 15 cm and 220 cm while indoors was 105 cm. The difference in mosquito collection between different outdoor and indoor heights was statistically significant (p < 0.0001). The optimal outdoor location of odour baited resting boxes from the wall of the house was 3 m. Conclusions: The results of these studies demonstrate an optimal method for sampling during surveillance and control programmes in rural villages of highlands and arid areas of Africa using inexpensive baits and boxes. Background Hematophagus insects locate their hosts following odours emanated by the hosts [1-5]. The Anopheles gambiae complex comprises two major malaria vector species An. gambiae Giles and An. arabiensis Patton while the An. funestus group include the major malaria vector, An. funestus Giles [6]. All three species are abundant in sub-Saharan Africa [6]. An. gambiae ss are anthropophilic while An. arabiensis are both anthropophilic as well as zoophilic depending on geographical location [6,7]. Human sweats and other animal body products attract haematophagus insects, such as tsetse * Correspondence: 1 Tropical Pesticides Research Institute, Division of Livestock and Human Diseases Vectors Control, Mosquito Section, P.O.Box 3024, Arusha, Tanzania Full list of author information is available at the end of the article flies [8,9]; mosquitoes [10-13] and sand flies [14]. Knowledge of these attractants plays a vital role in reducing human vector contact and in conducting surveillance studies. Resting boxes, either baited or un-baited, have been demonstrated to be suitable for the sampling of malaria vectors in different parts of Africa [15,16]. Fresh or decayed cattle urine baited resting boxes are effective in sampling An. Arabiensis, with efficacy even after seven days post-treatment [15,17]. This study deployed the fresh cattle urine in wet black cotton cloth to study the optimal trap placement and validate the effectiveness of the methodology. Three sets of experiments were conducted to determine: i) if traps with urine as bait perform better indoors or outdoors, and if people sleeping indoors had effects on the mosquito density; ii) the best height of trapping mosquitoes © 2010 Kweka et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Kweka et al. Parasites & Vectors 2010, 3:75 http://www.parasitesandvectors.com/content/3/1/75 indoors and outdoors; and iii) the efficiency of the trap located in three different distances from the wall of the house. Page 2 of 7 of the slopes of Mount Kilimanjaro, Northern Tanzania (3°21’S, 37°21’E). The study area is shown in Figure 1. House selection and characterization Materials and methods Study Area Description The study was conducted during the paddy transplantation season in the lower Moshi irrigation schemes, located 15 Km southern part of Moshi Town at the foot Ten houses were surveyed during the preparation stage of the study using CDC-miniature light traps for collecting mosquitoes from the surveyed houses. Four houses with high mosquito density were selected for the main study. In these selected houses, parameters such as eave Figure 1 Map showing the area where the sampling was performed at Point D in Lower Moshi irrigation schemes in Northern Tanzania. Kweka et al. Parasites & Vectors 2010, 3:75 http://www.parasitesandvectors.com/content/3/1/75 sizes, number of windows, wall and roof types and number of people sleeping in the house during experimental nights were recorded and compared with indoor mosquito density. Experimental design The study was a cross-sectional design in 3 by 3-Latin square for 20 days with an extra house fitted with CDC light trap for mosquitoes species abundance monitoring. One replicate was conducted for a period of three days; the study had a total of 6 replicates for 18 days. Two extra days were added to complement the lost time in two experimental days. In the first experiment, two baited resting boxes were used indoors and outdoors and placed at three different heights: 15 cm (H1); 105 cm (H2); and 220 cm (H3). Each house was used with one pair of boxes per night at one height. The second experiment was designed to determine the optimal outdoor location for odour baited resting boxes by selecting three distances from the external wall of the house: 0.3 m; 3 m; and 5 m. Each distance was tested per house per night in 3 by 3 Latin square for 20 days. The experiments were conducted for a period of twenty days between January and February, 2010. Animal husbandry, urine collection and preparation of the boxes Urine was collected in the morning from a mature female zebu cow and stored in a refrigerator at 4°C until the start of the experiment on the same evening. Boxes were prepared as previously described [15,17]. Mosquito sampling Trapping of mosquitoes by odour baited resting boxes and CDC-miniature light trap started at 1800 hours. The trapped mosquitoes were collected at 0600 hours in the following morning using a mechanical aspirator from the odour baited r (...truncated)