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A neglected aspect of the epidemiology of sleeping sickness: the propensity of the tsetse fly vector to enter houses.

Vale GA, Chamisa A, Mangwiro C, Torr SJ - PLoS Negl Trop Dis (2013)

Bottom Line: Doors and windows seemed about equally effective as entry points.Houses are attractive in themselves.Some of the tsetse attracted seem to be in a host-seeking phase of behavior and others appear to be looking for shelter from high temperatures outside.

View Article: PubMed Central - PubMed

Affiliation: Natural Resources Institute, University of Greenwich, Chatham, United Kingdom. valeglyn@gmail.com

ABSTRACT

Background: When taking a bloodmeal from humans, tsetse flies can transmit the trypanosomes responsible for sleeping sickness, or human African trypanosomiasis. While it is commonly assumed that humans must enter the normal woodland habitat of the tsetse in order to have much chance of contacting the flies, recent studies suggested that important contact can occur due to tsetse entering buildings. Hence, we need to know more about tsetse in buildings, and to understand why, when and how they enter such places.

Methodology/principal findings: Buildings studied were single storied and comprised a large house with a thatched roof and smaller houses with roofs of metal or asbestos. Each building was unoccupied except for the few minutes of its inspection every two hours, so focusing on the responses of tsetse to the house itself, rather than to humans inside. The composition, and physiological condition of catches of tsetse flies, Glossina morsitans morsitans and G. pallidipes, in the houses and the diurnal and seasonal pattern of catches, were intermediate between these aspects of the catches from artificial refuges and a host-like trap. Several times more tsetse were caught in the large house, as against the smaller structures. Doors and windows seemed about equally effective as entry points. Many of the tsetse in houses were old enough to be potential vectors of sleeping sickness, and some of the flies alighted on the humans that inspected the houses.

Conclusion/significance: Houses are attractive in themselves. Some of the tsetse attracted seem to be in a host-seeking phase of behavior and others appear to be looking for shelter from high temperatures outside. The risk of contracting sleeping sickness in houses varies according to house design.

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Related in: MedlinePlus

Plan view of Houses 1–3.In House 1 the internal glass windows and internal doors were always open; the external E door was always closed. The external W door of House 1, the external doors of Houses 2 and 3, and the external glass windows of all houses were open or closed as described in the text.
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pntd-0002086-g001: Plan view of Houses 1–3.In House 1 the internal glass windows and internal doors were always open; the external E door was always closed. The external W door of House 1, the external doors of Houses 2 and 3, and the external glass windows of all houses were open or closed as described in the text.

Mentions: All houses (Fig. 1) were 20–30 years old and were situated near the centre of the 30 ha clearing of the station, that contained short grass and only a few trees and bushes. Semi-evergreen and deciduous woodland occurred outside the clearing. Each of the houses was unoccupied during the studies, having been vacant for at least a year previously. The walls of the houses were 25 cm thick, made of cement blocks with air cavities, and painted inside and out with white PVA. The roofs were of gabled thatch (House 1) or consisted of corrugated and gently sloping sheets of asbestos (House 2) or galvanized iron, henceforth called tin (House 3) – the latter two “houses” were in fact unused kitchens about 3 m from large thatched houses, but they simulated the types of small building commonly used for field accommodation in central and southern Africa. For some studies the corrugated sheets were covered externally with a 15 cm layer of compressed grass to simulate thatching. Doors on all houses were windowless, hinged and wooden, 2 m tall and 0.8 m wide. Windows were of various width, extending between about 1 m to 2 m above floor level, steel framed and clear-glazed, with the exception of the large mosquito-netted windows along the veranda of House 1. About half of the area of each glazed window could be opened. The netted windows were permanently closed.


A neglected aspect of the epidemiology of sleeping sickness: the propensity of the tsetse fly vector to enter houses.

Vale GA, Chamisa A, Mangwiro C, Torr SJ - PLoS Negl Trop Dis (2013)

Plan view of Houses 1–3.In House 1 the internal glass windows and internal doors were always open; the external E door was always closed. The external W door of House 1, the external doors of Houses 2 and 3, and the external glass windows of all houses were open or closed as described in the text.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585122&req=5

pntd-0002086-g001: Plan view of Houses 1–3.In House 1 the internal glass windows and internal doors were always open; the external E door was always closed. The external W door of House 1, the external doors of Houses 2 and 3, and the external glass windows of all houses were open or closed as described in the text.
Mentions: All houses (Fig. 1) were 20–30 years old and were situated near the centre of the 30 ha clearing of the station, that contained short grass and only a few trees and bushes. Semi-evergreen and deciduous woodland occurred outside the clearing. Each of the houses was unoccupied during the studies, having been vacant for at least a year previously. The walls of the houses were 25 cm thick, made of cement blocks with air cavities, and painted inside and out with white PVA. The roofs were of gabled thatch (House 1) or consisted of corrugated and gently sloping sheets of asbestos (House 2) or galvanized iron, henceforth called tin (House 3) – the latter two “houses” were in fact unused kitchens about 3 m from large thatched houses, but they simulated the types of small building commonly used for field accommodation in central and southern Africa. For some studies the corrugated sheets were covered externally with a 15 cm layer of compressed grass to simulate thatching. Doors on all houses were windowless, hinged and wooden, 2 m tall and 0.8 m wide. Windows were of various width, extending between about 1 m to 2 m above floor level, steel framed and clear-glazed, with the exception of the large mosquito-netted windows along the veranda of House 1. About half of the area of each glazed window could be opened. The netted windows were permanently closed.

Bottom Line: Doors and windows seemed about equally effective as entry points.Houses are attractive in themselves.Some of the tsetse attracted seem to be in a host-seeking phase of behavior and others appear to be looking for shelter from high temperatures outside.

View Article: PubMed Central - PubMed

Affiliation: Natural Resources Institute, University of Greenwich, Chatham, United Kingdom. valeglyn@gmail.com

ABSTRACT

Background: When taking a bloodmeal from humans, tsetse flies can transmit the trypanosomes responsible for sleeping sickness, or human African trypanosomiasis. While it is commonly assumed that humans must enter the normal woodland habitat of the tsetse in order to have much chance of contacting the flies, recent studies suggested that important contact can occur due to tsetse entering buildings. Hence, we need to know more about tsetse in buildings, and to understand why, when and how they enter such places.

Methodology/principal findings: Buildings studied were single storied and comprised a large house with a thatched roof and smaller houses with roofs of metal or asbestos. Each building was unoccupied except for the few minutes of its inspection every two hours, so focusing on the responses of tsetse to the house itself, rather than to humans inside. The composition, and physiological condition of catches of tsetse flies, Glossina morsitans morsitans and G. pallidipes, in the houses and the diurnal and seasonal pattern of catches, were intermediate between these aspects of the catches from artificial refuges and a host-like trap. Several times more tsetse were caught in the large house, as against the smaller structures. Doors and windows seemed about equally effective as entry points. Many of the tsetse in houses were old enough to be potential vectors of sleeping sickness, and some of the flies alighted on the humans that inspected the houses.

Conclusion/significance: Houses are attractive in themselves. Some of the tsetse attracted seem to be in a host-seeking phase of behavior and others appear to be looking for shelter from high temperatures outside. The risk of contracting sleeping sickness in houses varies according to house design.

Show MeSH
Related in: MedlinePlus