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Bovine Leukosis Virus: What is it and What Does it Mean for Me?

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Dr. Ray Sweeney presented this material for DAIReXNET on October 14, 2015. To view the full presentation, please see our archived webinars page at http://www.extension.org/pages/15830/archived-dairy-cattle-webinars

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Bovine Leukosis Virus: What is it and What Does it Mean for Me?

  1. 1. DAIReXNET is proud to present today’s webinar: Bovine Leukosis Virus: What is it and What Does it Mean for Me? Dr. Ray Sweeney, University of Pennsylvania During this presentation. Dr. Ray Sweeney will discuss some of the big questions you may have about bovine leukosis virus. If you've been wondering about BLV, here’s where you learn all about it! The questions Dr. Sweeney will cover are: What is BLV? How is it spread? What happens when cows are infected with BLV? How is an infection diagnosed? Is there a treatment? How do we prevent infection? Today’s session will be recorded and archived at http://www.eXtension.org/pages/Archived_Dairy_Cattle_Webinars
  2. 2. Our Next Webinar: The Importance of Animal Handling for Dairy Cattle Dr. Kathryn Proudfoot, The Ohio State University November 5th, 2015 12:00 PM Central In this webinar, Dr. Proudfoot will discuss why using appropriate animal handling practices is so important for dairies! She will touch on cow memory and how that can influence fear responses to handlers.
  3. 3. For updates on webinars, new articles, and other great dairy information you can: Follow us on Facebook Sign up for our newsletter Follow us on Twitter
  4. 4. Bovine Leukosis Virus: What is it and What Does it Mean for Me? Raymond W. Sweeney, VMD University of Pennsylvania School of Veterinary Medicine New Bolton Center
  5. 5. Outline • What is BLV? • How do cows get BLV? • Who has BLV? • What happens to cows with BLV? – Disease? – Production? • What can I do to control BLV?
  6. 6. What is BLV? • Retrovirus – Bovine Leukosis Virus – “Bovine Leukemia Virus” – Enzootic Bovine Lymphosarcoma http://www.altmetric.com
  7. 7. What is BLV? • Related to: – Avian Leukosis virus – Feline Leukemia virus – Human T-cell lymphotrophic virus • Distant cousin to: – Caprine arthritis encephalitis virus – Human Immunodeficiency Virus http://www.altmetric.com/
  8. 8. Bovine Leukosis Virus • Conventional Wisdom: BLV does NOT infect people!!
  9. 9. Bovine Leukosis Virus • New Research: ??
  10. 10. BLV-Human Risk? • BLV virus has been found in human mammary tissue • More frequently found in samples from breast cancer than non-cancerous control samples PLOS-One, September 2, 2015
  11. 11. Retrovirus Facts • Infection is for Life! – Virus is always present in white blood cells
  12. 12. Retrovirus Facts • Long incubation period – Many infected individuals never become diseased
  13. 13. Outline • What is BLV? • How do cows get BLV? • Who has BLV? • What happens to cows with BLV? – Disease? – Production? • What can I do to control BLV?
  14. 14. BLV Transmission • BLV is transmitted by White Blood Cells, which carry the virus
  15. 15. Blood Transmission • Flies
  16. 16. Blood Transmission • Surgery, dehorning, needles
  17. 17. Blood Transmission • Rectal examination (pregnancy diagnosis)
  18. 18. Blood Cell Transmission-Other • Colostrum or milk • In-utero • Direct contact • Semen
  19. 19. Outline • What is BLV? • How do cows get BLV? • Who has BLV? • What happens to cows with BLV? – Disease? – Production? • What can I do to control BLV?
  20. 20. How Can We Tell Who Has BLV? • Antibodies in serum or milk are a reliable test for infection – Serum AGID or ELISA – Milk ELISA through DHIA – Bulk milk can be tested – EXCEPTION! Uninfected calves may still have antibody from colostrum up to 6 months of age
  21. 21. Outline • What is BLV? • How do cows get BLV? • Who has BLV? • What happens to cows with BLV? – Disease? – Production? • What can I do to control BLV?
  22. 22. BLV Infection • Cattle develop antibodies in blood within 6 weeks of infection. • Remain positive for life (AGID or ELISA) • The majority of cows with BLV infection NEVER GET SICK! • 2%-3% of cows develop cancer (lymphosarcoma), usually after 2-4 years • There is no practical treatment for BLV
  23. 23. Economic Impact • Death/culling due to cancer (lymphosarcoma) – 2%-3% of infected cows Abomasum Heart
  24. 24. Lymphosarcoma Spinal Cord Eye Uterus
  25. 25. What about outwardly healthy BLV cows? • Do BLV+ cows produce less milk? – Multiple studies with conflicting results – Many studies show no difference – Other studies show about 2% - 3% reduction in herd milk production --Annual Value of Production in BLV+ herds was reduced $59/cow– (Ott et al, 2003)
  26. 26. What about outwardly healthy BLV cows? • Some studies show an effect on immune function, which could cause: – Reduced response to vaccines? – Increased susceptibility to infections? – Research continues on this subject • Cull rates in BLV+ herds were higher in some studies, no difference in others • Conclusion: BLV might affect cow health in cows even if they don’t develop cancer
  27. 27. BLV Economic Impact • Export – Most countries require BLV- status – Screening springing heifers for export results in 10-20% refusal rate due to BLV+
  28. 28. Outline • What is BLV? • How do cows get BLV? • Who has BLV? • What happens to cows with BLV? – Disease? – Production? • What can I do to control BLV?
  29. 29. BLV Control: Why Should I? • Raise animals for export or stud – Foreign markets closed to BLV+ • Reduce losses from cows developing lymphosarcoma – Milk production – Carcass condemnation
  30. 30. BLV Control: Why Should I? (cont.) • What if human link is verified, or publicized? – Mandatory control – Public perception and effect on consumption of dairy products? • First step: Discuss testing (bulk milk, individual cow milk or serum) for BLV to see “how bad is it?”
  31. 31. BLV Control-Goals • IF I Have a BLV-free herd and want to maintain BLV-free status (rare in US!) – Maintain closed herd – Test all additions before admitting to premises
  32. 32. BLV Control Goals If my herd has BLV • Eradicate? – Test/segregate/control strategy • Not reasonable if high prevalence • Live with it – Do nothing • OK if not having financial impact now, but… • What if human link? • Begin steps to reduce infection – Delay/prevent infection in young stock to: • Reduce prevalence and reduce cancer losses • Raise BLV-negative heifers for sale • Easier to eradicate in future if need
  33. 33. Control Steps • Colostrum – Antibodies in colostrum from infected cow are protective to calf – Treat colostrum to kill virus but preserve antibodies • Freeze solid • Heat treat, 145oF for 30 minutes
  34. 34. Control Steps • Maintain separation of calves from adults • Individual hypodermic needle • Disinfect dehorning and tattooing instruments • Individual rectal sleeve
  35. 35. Conclusion • BLV is widespread in US Dairies • 3% of infected cows develop lymphosarcoma • Simple management steps can reduce the rate of infection • Economic effect of BLV probably less than other diseases, but… • Take steps now to reduce prevalence in case human link is confirmed
  36. 36. Thank you for participating in today’s discussion! Will you go one step further and help us make a better webinar? • Please click the following link and fill out our brief survey to help us improve the quality of our webinars: https://vte.co1.qualtrics.com/SE/?SID=SV_e4jnJDdGbc7pTUh

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