ISSN 2398-2993      

Enzootic bovine leukosis

obovis
Contributor(s):

Vetstream Ltd

Eoin Ryan

Synonym(s): EBL


Introduction

  • Cause: retrovirus bovine leukemia virus.
  • Signs: often no clinical signs, but may present with weight loss, ill thrift, loss of appetite, diarrhea, lymphadenopathy (painless), visible tumors may be observed, lumps on skin, congestive heart failure and/or paresis may occur secondary to tumors.
  • Diagnosis: cytology and histopathology.
  • Prognosis: hopeless.
A notifiable disease in the UK and notifiable in many European countries Notifiable diseases in the UK. If you suspect EBL, you should notify the relevant authorities immediately.

Pathogenesis

Etiology

  • Bovine leukemia virus (BLV), an exogenous C-type oncogenic retrovirus of the BLV-human T-lymphotropic virus group.

Pathophysiology

  • The disease can be transmitted from cows to calves during pregnancy or lactation. It is postulated that the virus may be spread by close contact with infected animals, but it is more likely to be transmitted directly via infected blood on equipment. Biting flies have also been implicated.
  • 30-70% of affected cattle will develop a persistent lymphocytosis (leukemia or preneoplastic syndrome) and remain clinically unaffected but may act as a reservoir for infection. Only 0.1% to 10% of persistently infected cattle will develop tumors.
  • BLV does not cause chronic viremia and has no preferred site of proviral integration. The resultant tumors are, however, typically monoclonal and have a single integration site.
  • The virus is thought to evade the host immune system via low levels of viral replication.

Epidemiology

  • Infection is often subclinical.
  • Once infected, the animal remains infected for life.
  • Surveys have indicated that up to 94.2% of US dairy herds may contain EBL positive cows.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Maezawa M, Watanabe K, Noriyuki H et al (2018) A clinical case of enzootic bovine leukosis in a 13-month-old Holdtein heifer. Japan J Vet Res 66 (3), 209-213 HUSCAP (pdf download).
  • Oguma K, Suzuki M & Sentsui H (2017) Enzootic bovine leukosis in a two-month-old calf. Virus Res 233, 120-124 PubMed.
  • Dimitrov P S, Todorova K S, Petrichev M H & Russev R V (2013) Bovine leukemia virus – pathogenicity in animals and potential impacts in humans. Cyprus Journal Sci 10 (2012), 101-109 ResearchGate.

Other sources of information

  • BCVA (2022) BCVA Webinar - Bovine Notifiable Diseases and Differential Diagnoses by Arthur Otter. BCVA, UK. Website: https://youtu.be.
  • Nagy D W (2022) Bovine Leukosis. In: MSD Manual. Merck & Co Inc, USA. Website: www.msdvetmanual.com.
  • APHIS (2021) Bovine Leukemia Virus (BLV). USDA, USA. Website: www.aphis.usda.gov.
  • The National Archives (2020) The Enzootic Bovine Leukosis (England) Order 2000. HM Government, UK. Website: www.legislation.gov.uk.
  • EFSA Panel on Animal Health and Welfare (2015) Enzootic Bovine Leukosis. EFSA Journal 13 (7), 4188 Website: https://efsa.onlinelibrary.wiley.com.

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