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Factors Affecting the Propensity of Tsetse Flies to Enter Houses and Attack Humans Inside: Increased Risk of Sleeping Sickness in Warmer Climates

Hargrove, John W., Vale, Glyn A, Chamisa, Andrew, Hall, David R., Mangwiro, Clement and Torr, Steve (2013) 'Factors Affecting the Propensity of Tsetse Flies to Enter Houses and Attack Humans Inside: Increased Risk of Sleeping Sickness in Warmer Climates'. PLoS Neglected Tropical Diseases, Vol 7, Issue 4, e2193.

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Abstract

Background

Sleeping sickness, or human African trypanosomiasis, is caused by two species of Trypanosoma brucei that are transmitted to humans by tsetse flies (Glossina spp.) when these insects take a bloodmeal. It is commonly assumed that humans must enter the normal woodland habitat of the flies to become infected, but recent studies found that tsetse frequently attack humans inside buildings. Factors affecting human/tsetse contact in buildings need identification.

Methodology/Principal Findings

In Zimbabwe, tsetse were allowed access to a house via an open door. Those in the house at sunset, and those alighting on humans in the house during the day, were caught using hand-nets. Total catches were unaffected by: (i) the presence of humans in the house and at the door, (ii) wood smoke from a fire inside the house or just outside, (iii) open windows, and (iv) chemicals simulating the odor of cattle or of humans. Catches increased about 10-fold with rising ambient temperatures, and during the hottest months the proportion of the total catch that was taken from the humans increased from 5% to 13%. Of the tsetse caught from humans, 62% consisted of female G. morsitans morstans and both sexes of G. pallidipes, i.e., the group of tsetse that normally alight little on humans. Some of the tsetse caught were old enough to be effective vectors.

Conclusion/Significance

Present results confirm previous suggestions that buildings provide a distinctive and important venue for transmission of sleeping sickness, especially since the normal repellence of humans and smoke seems poorly effective in such places. The importance of the venue would be increased in warmer climates.

Item Type: Article
Subjects: QT Physiology > Human Physiology > QT 150 Hot climates
QX Parasitology > Insects. Other Parasites > QX 505 Diptera
QX Parasitology > Protozoa > QX 70 Mastigophora. (e.g., Giardia. Trichomonas. Trypanosoma. Leishmania)
WA Public Health > Health Problems of Special Population Groups > WA 395 Health in developing countries
WB Practice of Medicine > Medical Climatology > WB 700 Medical climatology. Geography of disease
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 705 Trypanosomiasis
Faculty: Department: Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI): https://doi.org/10.1371/journal.pntd.0002193
Depositing User: Samantha Sheldrake
Date Deposited: 11 Jul 2013 09:27
Last Modified: 06 Feb 2018 13:06
URI: http://archive.lstmed.ac.uk/id/eprint/3424

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