Epidemiology of a Bluetongue outbreak in a sheep flock in Brazil.

In January 2013, an outbreak of Bluetongue (BT) a ecting a Lacaune sheep ock occurred in Vassouras, Rio de Janeiro state, Brazil. From March to August 2013, blood samples collection and clinical examination were performed monthly, in order to monitor the epidemiological pro le of Bluetongue virus (BTV) circulation and clinical disease in the ock. Agar gel immunodi usion (AGID) and reverse transcription polymerase chain reaction (RT-PCR) targeting BTV segment 10 were used as diagnostic assays. Additionally, insect trapping was conducted in the farm from May to July 2013. The ock serological prevalence to BTV was 80% since the rst month of monitoring, with a variation in the serological rate depending on the sheep age categories. The number of susceptible lambs increased with time, probably due to the decrease of passive immunity. Viral RNA was detected in blood samples, demonstrating viral circulation, prolonged viraemia, and potential source for virus transmission in the region, even in a dry and cool season. The presence of Culicoides pusillus and Culicoides insignis was con rmed in the farm. The emergence of this outbreak in a Brazilian endemic area for BTV emphasises an urgent need of animal surveillance and BTV epidemiological studies.

Bluetongue and other orbiviruses in South America: gaps and challenges.

South America (SA) has the ideal climatic conditions for occurrence of Bluetongue virus (BTV) and other orbiviruses. Based on serological evidence of BTV circulation, the virus is widespread across SA. However, little knowledge has been acquired about BTV origin and distribution, and circulation of specific serotypes is almost non­existent. The first barrier to a better understanding of Bluetongue (BT) in SA concerns its recognition in the field, as most infections of seropositive ruminants are unapparent in endemic areas. There are few reports on BTV isolation in SA, many of them from viraemic asymptomatic animals. Among the known competent BTV vectors, Culicoides insignis is the most abundant species in SA. However, information about biological characteristics and competence of various other Culicoides species described in SA is missing. The few reports on BT outbreaks lead to an underestimation of the disease impact on the continent economy. To overcome these major gaps, it is necessary to: improve diagnostic structure and disease recognition in the field; identify BTV serotypes and their distribution in different SA areas; and to study the biology and epidemiology of Culicoides. Furthermore, it is important to have a surveillance system for BT, as well as contingency plans for possible outbreaks in SA.