A quantitative risk assessment of West Nile virus introduction into Barbados / Una evaluación del riesgo cuantitativo de la introducción del virus del Nilo Occidental en Barbados

OBJECTIVE: To present a quantitative risk assessment of West Nile (WNV) virus introduction into Barbados, West Indies. DESIGN AND METHODS: Three possible modes were considered: a) WNV infected mosquitoes via air transport, by city of departure, b) WNV infected mosquitoes via marine transport and c) viraemic migratory, birds. We estimated the number of WNV infected migratory birds as the product of the proportion of migratory birds infected and the number of migratory birds entering Barbados in three taxonomic groups. We further estimated the number of days these birds would be infectious as: [formula: see text]. We then estimated the number (#) of infectious mosquito-days for mosquitoes entering Barbados via air transport as: # infected mosquitoes = (total flights per week/city) x (duration of WNV season) x (number of Culex mosquitoes aboard each flight) x (Culex mosquito WNV infection prevalence) x (vector competence index) x (days infectious). The number of infected mosquitoes entering Barbados via marine transport was estimated using a similar expression as for air transport, except that the number of airplanes and mosquitoes/airplane were substituted with the # of sea containers during a 22-week mosquito season and # of mosquitoes/container. RESULTS: Migratory birds (approximately 69-101 infected birds/year) were associated with the highest introductory risk followed by mode (a) (approximately 2 infected mosquitoes/year) and mode (b) (0. 004 infected mosquitoes/year). CONCLUSIONS: Migratory birds and mosquitoes via air are imminent threats for virus introduction. Impending co-circulation of West Nile virus and four strains of dengue virus may present new challenges for public health.

OBJETIVO: Presentar una valoración del riesgo cuantitativa de la introducción del Virus del Nilo Occidental (VNO) en Barbados, West Indies. MÉTODOS E DISEÑO: Se consideraron tres posibles modos: a) mosquitos infectados con el VNO vía transporte aéreo, por ciudad de salida, b) mosquitos infectados con el VNO vía transporte marítimo, y c) aves migratorias virémicas. Calculamos el número de aves migratorias infectadas con el VNO como el producto de la proporción de aves migratorias infectadas por el número de aves migratorias que entran a Barbados en tres grupos taxonómicos. Luego calculamos el número de días en que estas aves serían infecciosas, de la forma siguiente:[fórmula: ver en el texto].Calculamos entonces el número de días-mosquito infeccioso para los mosquitos que entran en Barbados mediante transporte aéreo, como sigue: # mosquitos infectados = (vuelos totales por semana/ciudad) x (duración de la estación del VNO) x (número de mosquitos Culex a bordo de cada vuelo) x (prevalencia de infección con VNO por mosquito Culex) x (índice de competencia del vector) x (días infecciosos). El número de mosquitos infectados que entraron a Barbados por vía del transporte marítimo fue calculado usando una fórmula similar a la usada en relación con el transporte aéreo, excepto que el número de aeroplanos y mosquitos/ aeroplanos fueron sustituidos con el # de contenedores marítimos durante una temporada de mosquitos de 22 semanas y el # de mosquitos/contenedor RESULTADOS: Las aves migratorias ~ (69-101 aves infectadas/años) estuvieron asociadas con el riesgo de introducción más alto seguido del modo (a) (~2 mosquitos infectados/año), y finalmente el modo (b) (0.004 mosquitos infectados/año). CONCLUSIONES: Las aves migratorias y los mosquitos por vía aérea representan una amenaza inminente de introducción de virus. La co-circulación inminente del Virus del Nilo Occidental y cuatro cepas de virus de dengue pueden presentar nuevos desafíos a la salud pública.

Collaborative research approaches to the role of wildlife in zoonotic disease emergence.

Emerging infectious diseases are a key threat to public health and the majority are caused by zoonotic pathogens. Here we discuss new collaborative approaches to understanding the process of zoonotic disease emergence that link veterinary medicine, public health, and ecological approaches: conservation medicine and one health. We demonstrate how studies on the underlying drivers of disease emergence (bushmeat hunting, wildlife trade, and deforestation) can provide ways to model, predict, and ultimately prevent zoonotic disease emergence and spread.

A quantitative risk assessment of West Nile virus introduction into Barbados.

OBJECTIVE: To present a quantitative risk assessment of West Nile (WNV) virus introduction into Barbados, West Indies. DESIGN AND METHODS: Three possible modes were considered: a) WNV infected mosquitoes via air transport, by city of departure, b) WNV infected mosquitoes via marine transport and c) viraemic migratory, birds. We estimated the number of WNV infected migratory birds as the product of the proportion of migratory birds infected and the number of migratory birds entering Barbados in three taxonomic groups. We further estimated the number of days these birds would be infectious as: [formula: see text]. We then estimated the number (#) of infectious mosquito-days for mosquitoes entering Barbados via air transport as: # infected mosquitoes = (total flights per week/city) x (duration of WNV season) x (number of Culex mosquitoes aboard each flight) x (Culex mosquito WNV infection prevalence) x (vector competence index) x (days infectious). The number of infected mosquitoes entering Barbados via marine transport was estimated using a similar expression as for air transport, except that the number of airplanes and mosquitoes/airplane were substituted with the # of sea containers during a 22-week mosquito season and # of mosquitoes/container. RESULTS: Migratory birds (approximately 69-101 infected birds/year) were associated with the highest introductory risk followed by mode (a) (approximately 2 infected mosquitoes/year) and mode (b) (0. 004 infected mosquitoes/year). CONCLUSIONS: Migratory birds and mosquitoes via air are imminent threats for virus introduction. Impending co-circulation of West Nile virus and four strains of dengue virus may present new challenges for public health.

Species interactions can explain Taylor's power law for ecological time series.

One of the few generalities in ecology, Taylor's power law, describes the species-specific relationship between the temporal or spatial variance of populations and their mean abundances. For populations experiencing constant per capita environmental variability, the regression of log variance versus log mean abundance gives a line with a slope of 2. Despite this expectation, most species have slopes of less than 2 (refs 2, 3-4), indicating that more abundant populations of a species are relatively less variable than expected on the basis of simple statistical grounds. What causes abundant populations to be less variable has received considerable attention, but an explanation for the generality of this pattern is still lacking. Here we suggest a novel explanation for the scaling of temporal variability in population abundances. Using stochastic simulation and analytical models, we demonstrate how negative interactions among species in a community can produce slopes of Taylor's power law of less than 2, like those observed in real data sets. This result provides an example in which the population dynamics of single species can be understood only in the context of interactions within an ecological community.