Whole genome sequencing and phylogenetic analysis of \u3ci\u3eBluetongue virus\u3c/i\u3e serotype 2 strains isolated in the Americas including a novel strain from the western United States

Bluetongue is a potentially fatal arboviral disease of domestic and wild ruminants that is characterized by widespread edema and tissue necrosis. Bluetongue virus (BTV) serotypes 10, 11, 13, and 17 occur throughout much of the United States, whereas serotype 2 (BTV-2) was previously only detected in the southeastern United States. Since 1998, 10 other BTV serotypes have also been isolated from ruminants in the southeastern United States. In 2010, BTV-2 was identified in California for the first time, and preliminary sequence analysis indicated that the virus isolate was closely related to BTV strains circulating in the southeastern United States. In the current study, the whole genome sequence of the California strain of BTV-2 was compared with those of other BTV-2 strains in the Americas. The results of the analysis suggest co-circulation of genetically distinct viruses in the southeastern United States, and further suggest that the 2010 western isolate is closely related to southeastern strains of BTV. Although it remains uncertain as to how this novel virus was translocated to California, the findings of the current study underscore the need for ongoing surveillance of this economically important livestock disease

Development of a Rift Valley fever real-time RT-PCR assay that can detect all three genome segments

Outbreaks of Rift Valley fever in Kenya, Madagascar, Mauritania, and South Africa had devastating effects on livestock and human health. In addition, this disease is a food security issue for endemic countries. There is growing concern for the potential introduction of RVF into non-endemic countries. A number of single-gene target amplification assays have been developed for the rapid detection of RVF viral RNA. This paper describes the development of an improved amplification assay that includes two confirmatory target RNA segments (L and M) and a third target gene, NSs, which is deleted in the Clone 13 commercial vaccine and other candidate vaccines. The assay also contains an exogenous RNA control added during the PCR setup for detection of amplification inhibitors. The assay was evaluated initially with samples from experimentally infected animals, after which clinical veterinary and human samples from endemic countries were tested for further evaluation. The assay has a sensitivity range of 66.7–100% and a specificity of 92.0–100% depending on the comparison. The assay has an overall sensitivity of 92.5%, specificity of 95% and a positive predictive value of 98.7%. The single-tube assay provides confirmation of the presence of RVFV RNA for improved confidence in diagnostic results and a “differentiate infected from vaccinated animals” (DIVA) – compatible marker for RVFV NSs – deleted vaccines, which is useful for RVF endemic countries, but especially important in non-endemic countries.This project was supported in part by the US Department of Agriculture, Agricultural Research Service Project #58-5430-005-00D through inter-agency agreements with the Science and Technology Directorate of the U.S. Department of Homeland Security under Award Number HSHQDC-07-00982 and the U.S. Department of State Biosecurity Engagement Program.http://www.elsevier.com/locate/jviromethb2013ab201