Changes

Bovine leukaemia virus is a [[:Category:Retroviridae|'''retrovirus''']] causing two specific diseases: '''Bovine lymphosarcoma''' and '''Persistent lymphocytosis'''.  

Bovine leukaemia virus is a [[:Category:Retroviridae|'''retrovirus''']] causing two specific diseases: '''Bovine lymphosarcoma''' and '''Persistent lymphocytosis'''.  

Bovine lymphosarcoma is fatal while persistent lymphocytosis is not usually so.  

Bovine lymphosarcoma is fatal while persistent lymphocytosis is not usually so. However, those affected with lymphosarcoma may or may not have been through the persistent lymphocytosis stage <ref>Radostitis et al (2007). Veterinary Medicine 10th Edition, Sauders Elsevier, Chapter 21</ref>.

Bovine leukosis is not transmissible to humans.

Bovine leukosis is not transmissible to humans.

==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.

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>

The most common presentation is that of '''enlarged lymph nodes''' which may cause multiple palpable swellings in the pharynx, flanks and limbs. This is often an early indicator of disease.

The most common presentation is that of '''enlarged lymph nodes''' which may cause multiple palpable swellings in the pharynx, flanks and limbs. This is often an early indicator of disease.

5-20% cases are peracute and present as '''sudden death'''. This is thought to be due to sequelae such as adrenal gland involvement or rupture of abomasal ulcers etc.

5-20% cases are peracute and present as '''sudden death'''. This may be due to sequelae such as adrenal gland involvement or rupture of abomasal ulcers etc.

Other signs are '''multisystemic''' and non-specific:

Other signs are '''multisystemic''' and non-specific:

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.

'''Agar Gel Immuno Diffusion (AGID)''' is the official standard test approved by most governments. This test is usually accurate by 2 - 4 weeks following infection. This test however cannot differentiate between infected cattle and those with passive immunity from colostrum.

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>.

Radioimmunoassay and serum or bulk milk [[ELISA testing|ELISA]] are also available. Antibodies may not be present for up to 12 weeks following onset of infection.

'''Agar Gel Immuno Diffusion (AGID)''' is the official standard test approved by most governments.  

PCR can also be performed on peripheral blood lymphocytes.

 

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]]