Emergence and Prevalence of Human Vector-Borne Diseases in Sink Vector Populations

Abstract

Vector-borne diseases represent a major public health concern in most tropical and subtropical areas, and an emerging threat for more developed countries. Our understanding of the ecology, evolution and control of these diseases relies predominantly on theory and data on pathogen transmission in large self-sustaining ‘source’ populations of vectors representative of highly endemic areas. However, there are numerous places where environmental conditions are less favourable to vector populations, but where immigration allows them to persist. We built an epidemiological model to investigate the dynamics of six major human vector borne-diseases in such non self-sustaining ‘sink’ vector populations. The model was parameterized through a review of the literature, and we performed extensive sensitivity analysis to look at the emergence and prevalence of the pathogen that could be encountered in these populations. Despite the low vector abundance in typical sink populations, all six human diseases were able to spread in 15–55% of cases after accidental introduction. The rate of spread was much more strongly influenced by vector longevity, immigration and feeding rates, than by transmission and virulence of the pathogen. Prevalence in humans remained lower than 5% for dengue, leishmaniasis and Japanese encephalitis, but substantially higher for diseases with longer duration of infection; malaria and the American and African trypanosomiasis. Vector-related parameters were again the key factors, although their influence was lower than on pathogen emergence. Our results emphasize the need for ecology and evolution to be thought in the context of metapopulations made of a mosaic of sink and source habitats, and to design vector control program not only targeting areas of high vector density, but working at a larger spatial scale.

Within-host competition and diversification of macro-parasites

“…We used a simple strategic 'core' model [59] that allows accounting for general features of macro-parasite lifestyle to specify the conditions for within-host competition to cause adaptive diversification. Although the description of the parasite life history was consistent with the lifestyle of the monogeneans used to confront our theory to existing phylogenetic studies, there are several lines along which to improve our theory and our understanding of the role of within-host competition in parasite diversity.…”

The Basic Reproduction Number for Chagas Disease Transmission Using Cellular Automata

“…Since triatomines undergo reduction in their life-time in bad places, the overall result is to lower the total number of opportunities for vectors to acquire and transmit the parasite. This result deserves to be investigated further as it could be an important determinant of the typical source-sink dynamics that underlie the transmission of many parasites [19]. Finally, spatial heterogeneity and random temporal variations are two central tenets of the ecology and evolution of many organisms that interact and show conceptual analogies [12,13].…”

“…Chagas disease is caused by infection with the parasite Trypanosoma cruzi which is transmitted by many species of bugs of the triatominae sub-family who feed on a large diversity of vertebrate hosts, a fraction of which only being able to transmit the parasite [14].The study of ecological dynamics of this disease requires strong potential in mathematical modelling which will help to understand the key of parasite transmission and to suggest efficient control strategies. The most predominant models are described by a set of differential equations which have been successfully used for studying several diseases such as SARS, Influenza A, Superbug, Malaria, Chagas and Dengue, see for example [1,5,15,19]. However, theses models do not take into account spatial factors and are not density dependent.…”

Bioefficacy of crude extract of Cyperus aromaticus (Family: Cyperaceae) cultured cells, against Aedes aegypti and Aedes albopictus mosquitoes

“…Presently mosquito borne diseases have become a global health problem with serious social and economic implications especially in tropical and subtropical countries [1,2] . Aedes aegypti (Linn.)…”