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Title: The effects of host-vector relationships and density dependence on the epidemiology of visceral leishmaniasis
Author: Dilger, Erin
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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In Latin America, visceral leishmaniasis (VL) is caused by infection with Leishmania infantum, an endemic but lethal parasite transmitted by Lutzomyia longipalpis sandflies. Multiple hosts are implicated in VL transmission; therefore sandfly biting preferences may be pivotal in determining transmission dynamics. Host preferences are poorly understood with simple preference-host density relationships being conventionally assumed. Combined modelling and fieldwork approaches were used to investigate the preference of sandflies for key host types (dogs, humans and chickens) and force of infection (FOI) over a range of vector and host densities. In Brazil, variable vector densities were (i) observed over a period of seasonal variation, and (ii) experimentally manipulated via “trapping out” (sustained CDCLT capture to reduce local vector density). Host density was also manipulated by (iii) the incremental introduction of chickens to experimental sheds. Results suggest that there is a significant link between alternative host density and the absolute and relative preference of sandflies for humans and dogs. Investigations also indicate that host choice has a vector density dependent element, which varies significantly and nonlinearly depending upon vector density. Meta-analysis and mathematical modelling of human and canine prevalences across Brazil also point toward variable transmission rates to these hosts attributable to density-dependent biting preferences observed in the field. These host choice dynamics ultimately combine to demonstrate the influence of host and vector densities on FOI on dogs and humans, but there are significant interactions between host and vector densities resulting in complex FOI relationships. Nonlinearities are likely explained by density dependent sandfly aggregation behaviour upon outdoor living hosts, such as chickens, as vector density rises. This preference behaviour may have far reaching implications for our understanding of transmission and control, and potentially indicate host density manipulation as an intervention measure.
Supervisor: Not available Sponsor: Biotechnology and Biological Sciences Research Council (BBSRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR Microbiology ; RA0421 Public health. Hygiene. Preventive Medicine ; RC Internal medicine