A Quantitative Risk Assessment Of West Nile Virus Introduction Into Barbados

zoonotics — Fri, 25 Jan 2008 13:34:27 +0000

AbstractObjective: To present a quantitative risk assessment of West Nile virus introduction into Barbados, West Indies. Design and Methods: We estimated the number of WNV infected migratory birds as the product of the proportion of infected migratory birds and the number of migratory birds entering Barbados in two taxonomic groups. We further estimated the number of days these birds would be infectious as:. 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 we substituted the number of airplanes and mosquitoes/airplane with the # of sea containers during a 22 week mosquito season and # of mosquitoes/container.Results: Three possible modes were considered: a) WNV infected mosquitoes via air transport, b) WNV infected mosquitoes via marine transport and c) viremic migratory birds. Mode (a) was analysed based on city of departure. Mode (c) (~69-101 infected birds/year) was associated with the highest introductory risk followed by mode (a) (~2 infected mosquitoes/year), and finally 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 4 strains of dengue virus may present new challenges for public health.

Avian influenza

zoonotics — Thu, 24 Jan 2008 20:03:00 +0000

Isolation and genetic characterization of influenza A viruses and a paramyxovirus from wild birds in Barbados: 2003-2004

Migratory waterfowl and shorebirds are regarded as the primordial reservoir of all influenza A viral subtypes and have been repeatedly implicated in avian influenza outbreaks in domestic poultry and swine. All of the 16 haemagglutinin (HA) and 9 neuraminidase (NA) influenza subtypes have been isolated from wild birds but waterfowl of the Order Anseriformes are the most commonly infected. Zoonotic transmission of an H5N1 avian influenza A virus to humans in 2003-present has generated increased public health and scientific interest in the prevalence and variability of influenza A viruses in wild birds and their potential threat to human health. Using 9-11 day old embryonated chicken egg (ECE) culture, virus isolation attempts were conducted on 168 cloacal swabs from varied resident, imported and migratory bird species in Barbados during July – October 2003 and 2004. Haemagglutination test, reverse transcription polymerase chain reaction (RT-PCR) and real time RT-PCR were used to screen all allantoic fluids for the presence of haemagglutinating agents, influenza A virus and Newcastle Disease virus (NDV) respectively. Two influenza A viruses and 1 NDV were isolated. An influenza virus isolation rate of 5.0 % (2/40) was observed in ducks (Anatidae). Data from phylogenetic analyses conducted on influenza A virus isolates support the tenet of genetic reassortment among avian influenza viruses in wild birds. This is the first report of the presence of influenza A viruses in migratory birds in the English-speaking Caribbean.

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A Quantitative Risk Assessment Of West Nile Virus Introduction Into Barbados

Avian influenza