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==Distribution==
==Distribution==
BLV is globally distributed, but prevalence widely varies. The UK is currently free of infection evidenced by government funded bulk milk antibody surveillance and investigations of tumours found in live or dead animals <ref> DEFRA (2010). http://archive.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/ebl/index.htm</ref>.
BLV is globally distributed, but prevalence widely varies. The UK is currently free of infection evidenced by government funded bulk milk antibody surveillance and investigations of tumours found in live or dead animals <ref> DEFRA (2010). http://archive.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/ebl/index.htm. Accessed 08/07/2012</ref>.
While 89% dairy operations in the USA showed seropositive results and 43.5% of all USA dairy cattle were seropositive <ref> USDA/APHIS/Veterinary Services, (1997). High prevalence of BLV in US dairy herds. Fort Collins, CO, USA: USDA: APHIS:VS Centers For Epidemiology and Animal Health.</ref>, seroprevalence in the EU rarely exceeds 0.5-1.5%. <ref>Lorenz, R. J., Straub, O. C. (1987) The epidemiology of enzootic bovine leukosis. In: Burny A, Mammerick, M, eds. Enzootic bovine leukosis and bovine leukemia virus. Boston, USA: Martinus Nijhoff Publishing, 51-68</ref>
While 89% dairy operations in the USA showed seropositive results and 43.5% of all USA dairy cattle were seropositive <ref> USDA/APHIS/Veterinary Services, (1997). High prevalence of BLV in US dairy herds. Fort Collins, CO, USA: USDA: APHIS:VS Centers For Epidemiology and Animal Health.</ref>, seroprevalence in the EU rarely exceeds 0.5-1.5%. <ref>Lorenz, R. J., Straub, O. C. (1987) The epidemiology of enzootic bovine leukosis. In: Burny A, Mammerick, M, eds. Enzootic bovine leukosis and bovine leukemia virus. Boston, USA: Martinus Nijhoff Publishing, 51-68</ref>
==Diagnosis==
==Diagnosis==
Identification of enlarged lymph nodes without a raised rectal temperature may instigate suspicion.
Identification of enlarged lymph nodes without a raised rectal temperature may instigate suspicion.
A range of serological tests are available although in calves none are able to distinguish between maternal and endogenous antibodies. Antibodies may not be present for up to 12 weeks following onset of infection. In the UK, seropositive calves were found to be due to the use of an imported colostrum replacer from an EBL endemic country <ref>DEFRA, 2010. http://archive.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/ebl/colostrum.htm. Accessed 08/07/2012</ref>.
A range of serological tests are available although in calves none are able to distinguish between maternal and endogenous antibodies. Antibodies may not be present for up to 12 weeks following onset of infection. In the UK, seropositive calves were found to be due to the use of an imported colostrum replacer from an EBL endemic country <ref>DEFRA, 2010. http://archive.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/ebl/colostrum.htm. Accessed 08/07/2012</ref>.
'''Agar Gel Immuno Diffusion (AGID)''' is the official standard test approved by most governments.
'''Agar Gel Immuno Diffusion (AGID)''' is the official standard test approved by most governments.
Radioimmunoassay and serum or bulk milk [[ELISA testing|ELISA]] are also available.
Radioimmunoassay and serum or bulk milk [[ELISA testing|ELISA]] are also available.
PCR can also be performed on peripheral blood lymphocytes. This test may be required to distinguish seropositive calves as either infected or having maternally derived antibodies.
PCR can also be performed on peripheral blood lymphocytes. This test may be required to distinguish seropositive calves as either infected or having maternally derived antibodies.
Multiple, firm white tumours may be present in any organ on post-mortem examination. In young animals, the common sites are the kidneys, thymus, liver, spleen, and lymph nodes. In adults, the heart, abomasum, and spinal cord are often involved.
Multiple, firm white tumours may be present in any organ on post-mortem examination. In young animals, the common sites are the kidneys, thymus, liver, spleen, and lymph nodes. In adults, the heart, abomasum, and spinal cord are often involved.
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{{review}}
{{Nick Lyons
|date = July 8, 2012}}
[[Category:Retroviridae]]
[[Category:Retroviridae]]
[[Category:Lymphoreticular and Haematopoietic Diseases - Cattle]]
[[Category:Lymphoreticular and Haematopoietic Diseases - Cattle]]
[[Category: CABI Expert Review]]
[[Category: CABI Expert Review]]
[[Category:Nick L]]
[[Category:Nick Lyons reviewed]]