Towards an early warning system for Rhodesian sleeping sickness in Savannah Areas : man-like traps for tsetse flies
Date
2012-12
Journal Title
Journal ISSN
Volume Title
Publisher
Public Library of Science
Abstract
Background: In the savannahs of East and Southern Africa, tsetse flies (Glossina spp.) transmit Trypanosoma brucei
rhodesiense which causes Rhodesian sleeping sickness, the zoonotic form of human African trypanosomiasis. The flies feed
mainly on wild and domestic animals and are usually repelled by humans. However, this innate aversion to humans can be
undermined by environmental stresses on tsetse populations, so increasing disease risk. To monitor changes in risk, we
need traps designed specifically to quantify the responsiveness of savannah tsetse to humans, but the traps currently
available are designed to simulate other hosts.
Methodology/Principal Findings: In Zimbabwe, two approaches were made towards developing a man-like trap for
savannah tsetse: either modifying an ox-like trap or creating new designs. Tsetse catches from a standard ox-like trap used
with and without artificial ox odor were reduced by two men standing nearby, by an average of 34% for Glossina morsitans
morsitans and 56% for G. pallidipes, thus giving catches more like those made by hand-nets from men. Sampling by
electrocuting devices suggested that the men stopped flies arriving near the trap and discouraged trap-entering responses.
Most of human repellence was olfactory, as evidenced by the reduction in catches when the trap was used with the odor of
hidden men. Geranyl acetone, known to occur in human odor, and dispensed at 0.2 mg/h, was about as repellent as human
odor but not as powerfully repellent as wood smoke. New traps looking and smelling like men gave catches like those from
men.
Conclusion/Significance: Catches from the completely new man-like traps seem too small to give reliable indices of human
repellence. Better indications would be provided by comparing the catches of an ox-like trap either with or without artificial
human odor. The chemistry and practical applications of the repellence of human odor and smoke deserve further study.
Description
CITATION: Vale, G. A., et al. 2012. Towards an early warning system for Rhodesian sleeping sickness in Savannah Areas : man-like traps for tsetse flies. PLoS Neglected Tropical Diseases, 6(12): 1-9, doi:10.1371/journal.pntd.0001978.
The original publication is available at http://journals.plos.org/plosntds
The original publication is available at http://journals.plos.org/plosntds
Keywords
Tsetse-flies, Trypanosoma brucei rhodesiense, Human repellence, Ox-like trap, Man-like trap, African trypanosomiasis, Trapping
Citation
Vale, G. A., et al. 2012. Towards an early warning system for Rhodesian sleeping sickness in Savannah Areas : man-like traps for tsetse flies. PLoS Neglected Tropical Diseases, 6(12): 1-9, doi:10.1371/journal.pntd.0001978