Mosquito trap data from Kilombero Valley in Tanzania - a global hotspot for malaria.
Since 2007, field entomologists working at Ifakara Health Institue (IHI) and at the University of Glasgow have been trapping and collecting primary malaria vectors for four villages in the Kilombero Valley: Lupiro, Kidugalo, Minepa and Sagamaganga. Trapped mosquitoes were identified to species level (Anopheles gambiae and A funestus), their sex recorded (male or female) and their abdominal status (fed or unfed) noted. When available, the daily mosquito data was consistently linked to micro climate data logger data (weather conditions on site, including averaged, minimum and maximum daytime and night time values for temperature, humidity and vapour pressure deficit). This long record allows exploring the relationship between malaria vector dynamics and related environmental conditions.
Publication date: 2018-03-08
Trapped malaria mosquitoes were identified to species level (Anopheles gambiae, Anopheles funestus and Anopheles coustani), their sex recorded (male or female) and their abdominal status (fed or unfed) noted for four villages in the Kilombero Valley, Lupiro, Kidugalo , Minepa and Sagamaganga. When available, the daily mosquito data was consistently linked to micro climate data logger data (including averaged, minimum and maximum daytime and night time values for temperature in Celcius and relative humidity in percentage). All households in a selected village were sampled monthly for one week (from Monday to Friday) before moving on to the next village. Consequently, all selected villages were visited at least five days per month over the project period (06/2016->09/2017). Two different trapping methods were employed: standard CDC traps and Mosquito Electrocuting Traps (MET).
(1) Standard CDC traps were left overnight inside the studied households (indoor trapping - total night catch from 18pm to 6am). CDC light traps and batteries - CDC miniature light trap, Model 512, John Hock, Florida, USA and 12V batteries were used. Light of a small bulb attracts mosquitoes to the trap and a small rotating computer fan then sucks the insects into a collection bag or cup below. The Model 512 requires ca. 320 mAmps per hour to operate at 6.0-6.3 volts DC. We used sealed-electrolyte lead-acid 12V batteries provide power for at least 3 night's operation. The 12 volt batteries for the CDC traps were also checked at the beginning of every trapping night by voltmeter to ensure they are adequately charged.
(2) Mosquito Electrocuting Traps (MET) were used to estimate mosquito abundance hourly data from 6pm to 6am (one indoor and one outdoor from 18pm to 6am). MET traps and batteries - The MET is composed of four 35 x 35 cm panels, arranged to form a square cavity into which human volunteers' legs are placed. The panels hold sets of vertical parallel stainless steel wires spaced 5 mm apart, which are electrically connected to a 24V battery-powered stable direct current (DC) power source (e.g. sealed-electrolyte lead-acid 12V batteries), thereby creating an electric potential between the wires to kill mosquitoes trying to pass through the wires, but without destroying the specimen. The power is supplied at low output, sufficient to kill mosquitoes on contact but not harming the volunteer. Dead mosquitoes were collected hourly in plastic cups and identified the following morning. Due to sporadic difficulties with the MET equipment, data from the MET collection is missing at the beginning of the study and for three weeks in June 2017. The voltage of the electric current on each panel of the grids of the MET traps was measured twice nightly using a voltmeter. All abundance data was converted from paper sheets to excel spreadsheets. A subset of mosquitoes collected was tested for malaria parasites and to verify the species using PCR/ELISA tests, thus validating the identification process in the field.
Indoor temperature and humidity were recorded with tiny tag data loggers (Tiny Tag plus 2; Gemini data loggers, UK, Ltd) placed inside houses on each night of sampling, approximately 1m above the ground. The tiny tag data loggers are calibrated annually by Gemini data loggers, UK, Ltd and every weekend by placing all loggers in the same room and checking their recordings are identical. The data was downloaded weekly and converted into excel spreadsheet.