▁unf air ly ▁dismiss ed ▁M s ▁Se ym our - Smith ▁ ▁Category : Un ited ▁Kingdom ▁labour ▁case ▁law ▁Category : H ouse ▁of ▁L ords ▁cases ▁Category : C ourt ▁of ▁Justice ▁of ▁the ▁European ▁Union ▁case ▁law ▁Category : 2 0 0 0 ▁in ▁case ▁law ▁Category : 2 0 0 0 ▁in ▁British ▁law ▁Category : Europe an ▁Union ▁labour ▁case ▁law <0x0A> </s> ▁B ov ine ▁le uk emia ▁virus ▁( BL V ) ▁is ▁a ▁retro vir us ▁which ▁causes ▁en zo otic ▁b ov ine ▁le uk osis ▁in ▁cattle . ▁It ▁is ▁closely ▁related ▁to ▁the ▁human ▁T ‑ ly m ph otrop ic ▁virus ▁type ▁ 1 ▁( HT L V - I ). ▁B L V ▁may ▁integrate ▁into ▁the ▁genom ic ▁DNA ▁of ▁B ‑ ly m ph ocy tes ▁as ▁a ▁DNA ▁intermediate ▁( the ▁prov irus ), ▁or ▁exist ▁as ▁un integr ated ▁circular ▁or ▁linear ▁forms . ▁Besides ▁struct ural ▁and ▁en zym atic ▁gen es ▁required ▁for ▁vir ion ▁production , ▁B L V ▁contains ▁an ▁on c ogene ▁coding ▁for ▁a ▁protein ▁called ▁Tax ▁and ▁express es ▁micro R N As ▁of ▁unknown ▁function . ▁In ▁cattle , ▁most ▁inf ected ▁animals ▁are ▁asympt om atic ; ▁le uk emia ▁is ▁rare ▁( about ▁ 5 % ▁of ▁inf ected ▁animals ), ▁but ▁l ym ph op rol ifer ation ▁is ▁more ▁frequent ▁( 3 0 %). ▁ ▁D ise ase ▁in ▁cattle ▁ ▁Trans mission