Here we set out to standardize long-lasting, visually-attractive devices for Glossina swynnertoni, a vector of both human and animal trypanosomiasis in open savannah in Tanzania and Kenya, and in neighbouring conservation areas used by pastoralists. The goal was to determine the most practical device/material that would induce the strongest landing response in G. swynnertoni for use in area-wide population suppression of this fly with insecticide-impregnated devices.
Methods and Findings
Trials were conducted in wet and dry seasons in the Serengeti and Maasai Mara to measure the performance of traps and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a simple enumerator at these remote locations to compare trapping efficiencies of devices. Independent of season or presence of chemical baits, targets in phthalogen blue or turquoise blue cloth with adhesive film were the best devices for capturing G. swynnertoni in all situations, catching up to 19 times more flies than pyramidal traps. Baiting with chemicals did not affect the relative performance of devices. Fly landings were two times higher on 1 m2 blue-black targets as on pyramidal traps when equivalent areas of both were covered with adhesive film. Landings on 1 m2 blue-black targets were compared to those on smaller phthalogen blue 0.5 m2 all-blue or blue-black-blue cloth targets, and to landings on all-blue plastic 0.32–0.47 m2 leg panels painted in phthalogen blue. These smaller targets and leg panels captured equivalent numbers of G. swynnertoni per unit area as bigger targets.
Leg panels and 0.5 m2 cloth targets show promise as cost effective devices for management of G. swynnertoni as they can be used for both control (insecticide-impregnated cloth) and for sampling (rigid plastic with insect glue or adhesive film) of populations.
Glossina swynnertoni is restricted to open savannah in north-western Tanzania and south-western Kenya, where it is a vector of both human and animal trypanosomiasis in wildlife reserves and in neighbouring conservation areas used by pastoralists. Despite the challenge to minimize disease transmission through effective management of the vector in the presence of abundant wildlife reservoirs, little has been done to test the efficacy of modern tsetse traps or targets for controlling G. swynnertoni. We made field tests in the Serengeti and Maasai Mara to determine the most visually-attractive, long-lasting and practical object that induces the strongest landing response in G. swynnertoni. Fly landings were twice as high on 1 m2 blue-black targets as on pyramidal traps when equivalent areas of these devices were covered with adhesive film. Furthermore, blue leg panels in either cloth or plastic and blue or blue-black-blue cloth targets under half the size of traditional targets captured tsetse at equivalent numbers per unit as the latter. These smaller targets and leg panels show promise as cost-effective devices for management of G. swynnertoni populations as they can be used for both control (insecticide-impregnated cloth) and monitoring of this species (rigid plastic with insect glue or adhesive film).