Eradication of bovine leukosis virus on a diary farm through improved virus detection/Iskorjenjivanje enzootske leukoze goveda na farmi mlijecnih krava primjenom razlicitih dijagnostickih postupaka

The aim of this study was to perform a diagnosis and molecular characterisation of bovine leukosis virus (BLV) on a Croatian dairy farm. For that purpose we compared the diagnostic tools used in our study, made sequence and phylogenetic analysis of our BLV and tried to describe the difficulties in the process of EBL eradication on the examined farm after reintegration into Croatian territory after the war. From 1998 to 2008 blood samples from a dairy farm in the North-eastern part of Croatia were tested serologically using AGID and ELISA. In 2002, 2003 and 2004 37%, 22% and 10% of animals were serologically positive, respectively. After the initial eradication steps, the disease reappeared in 2008, when all examined blood samples reacted positively in BLV-specific nested PCR. Finally, at the end of 2010, after an extended eradication program, which included the implementation of PCR together with regular ELISA testing for detection of positive animals, the farm obtained the status of "free of BLV". Sequence and phylogenetic analysis of 524-nt fragment of BLV env gp51 encoding gene showed the greatest identity with the Croatian BLV genotype 8 isolates, so it was phylogenetically clustered with those isolates. Key words: bovine leukosis virus, gene env, gp51, ELISA, nested PCR, phylogenetic analysis Cilj istrazivanja bio je dijagnosticirati i molekulski karakterizirati virus enzootske leukoze goveda (VELG) na jednoj hrvatskoj farmi mlijecnih krava. U tu svrhu usporedeni su dijagnosticki postupci rabljeni u istrazivanju te je napravljena analiza nukleotidnog slijeda VELG i filogenetska analiza. Opisane su i poteskoce u provodenju mjera iskorjenjivanja na pretrazivanoj farmi tijekom mirne integracije ovog podrucja Hrvatske poslije domovinskog rata. Od 1998. do 2008. uzimani su uzorci krvi krava na farmi mlijecnih krava smjestenoj u sjeveroistocnom dijelu Hrvatske te seroloski pretrazivani gel difuzijskim precipitacijskim (GDP) i imunoenzimnim testom. U 2002. na VELG bilo je pozitivno 37%, 2003. 22%, a 2004. 10% zivotinja. Godine 2008. svi pretrazeni uzorci krvi bili su pozitivni pretragom lancanom reakcijom polimerazom. Naposljetku, krajem 2010. nakon produzenih mjera iskorjenjivanja sto su ukljucivale primjenu lancane reakcije polimerazom istodobno s redovitim pretrazivanjem imunoenzimnim testom kako bi se identificirale sve zivotinje pozitivne na ELG, farma je postala slobodna od ELG. Na osnovi filogenetske analiza odsjecka VELG sto kodira za gen env gp51 iz