Is the even distribution of insecticide-treated cattle essential for tsetse control? Modelling the impact of baits in heterogeneous environments
Torr, Steve J. and Vale, Glyn A. (2011) Is the even distribution of insecticide-treated cattle essential for tsetse control? Modelling the impact of baits in heterogeneous environments. PLOS Neglected Tropical Diseases, 5 (10):e1360. ISSN 1935-2727 (Print), 1935-2735 (Online) (doi:10.1371/journal.pntd.0001360)
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Eliminating Rhodesian sleeping sickness, the zoonotic form of Human African Trypanosomiasis, can be achieved only through interventions against the vectors, species of tsetse (Glossina). The use of insecticide-treated cattle is the most cost-effective method of controlling tsetse but its impact might be compromised by the patchy distribution of livestock. A deterministic simulation model was used to analyse the effects of spatial heterogeneities in habitat and baits (insecticide-treated cattle and targets) on the distribution and abundance of tsetse.
The simulated area comprised an operational block extending 32 km from an area of good habitat from which tsetse might invade. Within the operational block, habitat comprised good areas mixed with poor ones where survival probabilities and population densities were lower. In good habitat, the natural daily mortalities of adults averaged 6.14% for males and 3.07% for females; the population grew 8.46in a year following a 90% reduction in densities of adults and pupae, but expired when the population density of males was reduced to <0.1/km2; daily movement of adults averaged 249 m for males and 367 m for females. Baits were placed throughout the operational area, or patchily to simulate uneven distributions of cattle and targets. Gaps of 2–3 km between baits were inconsequential provided the average imposed mortality per km2 across the entire operational area was maintained. Leaving gaps 5–7 km wide inside an area where baits killed 10% per day delayed effective control by 4–11 years. Corrective measures that put a few baits within the gaps were more effective than deploying extra baits on the edges.
The uneven distribution of cattle within settled areas is unlikely to compromise the impact of insecticide-treated cattle on tsetse. However, where areas of >3 km wide are cattle-free then insecticide-treated targets should be deployed to compensate for the lack of cattle.
|Additional Information:|| First published: October 18, 2011.  Published as: PLOS Neglected Tropical Diseases, (2011), Vol. 5, (10) : e1360.  Copyright: © 2011 Torr, Vale. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.  PLOS Neglected Tropical Diseases is an open-access journal.  The definitive version can be accessed at PLOS Neglected Tropical Diseases - http://dx.doi.org/10.1371/journal.pntd.0001360|
|Uncontrolled Keywords:||tsetse, trypanosomiasis, Glossina, sleeping sickness, population model, modelling, vector ecology|
|Subjects:||S Agriculture > SF Animal culture|
|School / Department / Research Groups:||Natural Resources Institute|
Faculty of Engineering & Science > Natural Resources Institute
Natural Resources Institute > Agriculture, Health & Environment
Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment
Natural Resources Institute > Pest Behaviour Research Group
Faculty of Engineering & Science > Natural Resources Institute > Pest Behaviour Research Group
|Last Modified:||02 Jul 2013 16:45|
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