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. 2012;6(5):e1615.
doi: 10.1371/journal.pntd.0001615. Epub 2012 May 15.

Modeling the control of trypanosomiasis using trypanocides or insecticide-treated livestock

Affiliations

Modeling the control of trypanosomiasis using trypanocides or insecticide-treated livestock

John W Hargrove et al. PLoS Negl Trop Dis. 2012.

Abstract

Background: In Uganda, Rhodesian sleeping sickness, caused by Trypanosoma brucei rhodesiense, and animal trypanosomiasis caused by T. vivax and T. congolense, are being controlled by treating cattle with trypanocides and/or insecticides. We used a mathematical model to identify treatment coverages required to break transmission when host populations consisted of various proportions of wild and domestic mammals, and reptiles.

Methodology/principal findings: An Ro model for trypanosomiasis was generalized to allow tsetse to feed off multiple host species. Assuming populations of cattle and humans only, pre-intervention Ro values for T. vivax, T. congolense, and T. brucei were 388, 64 and 3, respectively. Treating cattle with trypanocides reduced R(0) for T. brucei to <1 if >65% of cattle were treated, vs 100% coverage necessary for T. vivax and T. congolense. The presence of wild mammalian hosts increased the coverage required and made control of T. vivax and T. congolense impossible. When tsetse fed only on cattle or humans, R(0) for T. brucei was <1 if 20% of cattle were treated with insecticide, compared to 55% for T. congolense. If wild mammalian hosts were also present, control of the two species was impossible if proportions of non-human bloodmeals from cattle were <40% or <70%, respectively. R(0) was <1 for T. vivax only when insecticide treatment led to reductions in the tsetse population. Under such circumstances R(0)<1 for T. brucei and T. congolense if cattle make up 30% and 55%, respectively of the non-human tsetse bloodmeals, as long as all cattle are treated with insecticide.

Conclusions/significance: In settled areas of Uganda with few wild hosts, control of Rhodesian sleeping sickness is likely to be much more effectively controlled by treating cattle with insecticide than with trypanocides.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. The effect on trypanosomiasis of treating cattle with trypanocides.
A. The effect on the basic reproductive value, R 0, for three species of trypanosome of treating a proportion of cattle with trypanocides such that the cattle have zero probability of being infected with trypanosomes of any species. B. Rescaled version showing details of change in R 0 for T. brucei and also the effect of decreasing the tsetse feeding interval from 4 days to 2.5 days.
Figure 2
Figure 2. How the presence of wild hosts affects the control of T. brucei using trypanocides.
The relationship between the proportion of wild mammals among all non-human hosts and the basic reproductive value (R 0) for T. brucei. It is assumed that any cattle present are all, continuously, on a trypanocide with 100% efficacy.
Figure 3
Figure 3. The effect on trypanosomiasis of treating cattle with insecticide.
A. The effect on the basic reproductive value, R 0, for three species of trypanosome of treating a proportion of cattle with insecticide that kills any fly attempting to feed off a treated animal. B. Detail for T. brucei, showing the differential effects on R 0 for cattle and for humans.
Figure 4
Figure 4. How the presence of wild hosts affects the control of T. brucei using insecticide.
The relationship between the basic reproductive value, R 0, and the proportion of cattle among all non-human mammalian hosts in the situation where a proportion of cattle are treated with insecticide that kills any fly attempting to feed off that animal. A. T. vivax and T. congolense in cattle and wildlife - where all cattle are treated with insecticide. B. T. brucei; total R 0 in humans, cattle and wildlife for situations where different proportions of the cattle are treated with insecticide.
Figure 5
Figure 5. The effect of vector population reduction on the control of T. brucei using insecticide.
The relationship between the basic reproductive value, R 0, and the proportion of cattle among all non-human mammalian hosts in the situation where all cattle are treated with an insecticide that kills any fly attempting to feed off that animal. The dotted lines show the further change in R 0 in the circumstance that the imposed mortality results in a decline in the tsetse population.

References

    1. Simarro PP, Diarra A, Postigo JAR, Franco JR, Jannin JG. The Human African Trypanosomiasis Control and Surveillance Programme of the World Health Organization 2000–2009: The Way Forward. Plos Neglected Tropical Diseases. 2011;5:7. - PMC - PubMed
    1. Fevre EM, von Wissmann B, Welburn SC, Lutumba P. The Burden of Human African Trypanosomiasis. Plos Neglected Tropical Diseases. 2008;2 - PMC - PubMed
    1. Kristjanson P, Swallow B, Rowlands G, Kruska R, de Leeuw P. Measuring the costs of African animal trypanosomosis, the potential benefts of control and returns to research. Agricultural Systems. 1999;59:79–98.
    1. Vale GA, Torr SJ. Development of bait technology to control tsetse. In: I. Maudlin PHHaMAM., editor. The Trypanosomiases. Wallingford: CABI; 2004. pp. 509–523.
    1. Allsopp R, Hursey BH. Insecticidal control of tsetse. In: Maudlin I, Holmes PH, Miles MA, editors. The Trypanosomiases. Wallingford: CABI; 2004. pp. 491–507.

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