RAPID DIAGNOSIS OF BLUETONGUE VIRUS SEROTYPES 2 AND 12 INFECTION BY REVERSE TRANSCRIPTION LOOP-MEDIATED ISOTHERMAL AMPLIFICATION

Bluetongue (BT), an arthropod-borne viral disease, is caused by the bluetongue virus (BTV), belonging to the genus Orbivirus of the family Reoviridae. Most species of ruminants are susceptible to BTV, but most infections go subclinical. These 'reservoir hosts' may potentially further increase the viral transmission and expansion of the disease; thus, detection of subclinical infection is important. To detect the BTV, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed using primers targeted to six regions of the segment 5 (NS1) gene of the BTV2/KM/2003. The assay was completed in 1 h at a temperature 65°C, and the products were specifically digested with MboII enzyme presented in the target region. The in vitro sensitivity of the RT-LAMP was 100 copies, characterized by a qRT-PCR. The RT-LAMP did not cross-react with four tested common ruminant infectious agents, namely foot and mouth disease virus, goat pox virus, bovine herpesvirus 1, and Clostridium perfrigens. The RT-LAMP was applied to whole blood samples from 15 clinically healthy dairy cattle, and was able to detect BTV from 3/15 animals, and in particular 1 of the 3 animals was seronegative by cELISA. Positive RT-LAMP samples were reproducible. This RT-LAMP provides a simple, efficient, and sensitive method to specifically detect BTV and is suitable for the screening of field samples with a potential to pick up subclinical infection. The alignments of the outer primer region indicated matches of > 85% with 18 out of 26 BTV serotypes, implying its potential as universal primers.