First phylogenetic analysis of bluetongue virus serotype 4 field isolates from Argentina.

DANILO LEGISA; FERNANDA GONZALEZ; GABRIEL DÉSTEFANO; ARIEL PEREDA; MARIA JOSE DUS SANTOS

Congreso; 11th International Symposium on Double-Stranded RNA Viruses; 2012

 Bluetongue virus (BTV) is the prototype member of the genus Orbivirus within the family Reoviridae. The disease affects domestic and wild ruminants, and although severe forms of the disease are most frequent in sheep and white-tailed deer, clinical signs can also occur in cattle, goats and camelids. Although infection is often unapparent in these other species, they can act as reservoirs, remaining viremic for several months (particularly cattle)1. Bluetongue is listed as a ?notifiable disease? by the Office International des Epizooties (OIE). The sanitary and economic impact of BTV infection involves loss of condition, reduced milk yield, infertility and abortion, as well as indirect costs associated with international trade restrictions and the surveillance requirements imposed to limit the spread of the virus. BTV infection of ruminants is not contagious; the virus is transmitted among hosts almost entirely by the bites of certain species of Culicoides biting midges. Thus, the distribution of BTV is restricted to areas where competent vector species are present, and transmission is limited to those times of the year when climatic conditions are appropriate and adult insects are active. The virus genome is composed of ten double-stranded RNA segments. Seven of the viral proteins (VP1 to VP7) are structural and form the double-shelled virus particle. At least four non-structural proteins (NS1, NS2 and NS3, NS3A and NS4) have been identified2.  Information about the presence of BTV in the Americas can be divided according to the amount of data available. There are substantial data about North America, Central America and the Caribbean. Serotypes 1, 2, 3, 5, 6, 10, 11, 13, 14, 17, 19, 22 and 24 have been detected in North America, whereas serotypes 1, 3, 4, 6, 8, 12 and 17 have been identified in Central America and the Caribbean.3 However, in South America, information regarding detection of BTV is limited to very few reports. Serological evidence for the presence of BTV has been reported in Peru 4, Argentina5, Brazil6, Ecuador7 and Chile8. Using serological techniques, the serotypes probably present in South America are: 4, 6, 14,17, 19 and 20 in Brazil, 12, 14 and 17 in Colombia, 14 and 17 in Guyana and 6, 14 and 17 in Suriname. Brazil and Argentina are the only countries in South America where BTV has been isolated9, 10. In Argentina, two serological surveys (one between 1995 and 1996 and the other in 1998) indicated that Misiones province and two Departments of Corrientes province, in the northeast of the country, were seropositive. During those surveys, BTV was isolated at the National Institute of Agricultural Technology (INTA) from the blood of sentinel cattle without clinical signs and the serotype was determined as 4 by SN and RT-PCR10. Two new isolates, obtained as part of the present work, were typified by RT-PCR and sequencing.