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Bovine Leukosis : Are We Up To The Challenge

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  1. Bovine Leukosis: Are We Up To The Challenge Greg Keefe DVM MSc MBA OmidNekouei DVM

  2. Introduction • Terminology • Enzootic Bovine Leukosis (EBL) = “the disease” • Bovine Leukemia Virus (BLV) = “the virus” • Spread • Blood or other sources of “blood cells” • Not a free virus – needs to be in cells • Any blood contact – Needles, dehorners, bloody trimming knives, rectal sleeves • Also possible - colostrum, milk, reproductive procedures, in-utero (before birth)exposure

  3. Introduction • Progression of Leukosis • Infection and development of permanent carrier state • Increase in circulating white blood cells – about 30% of animals develop this stage • Tumors – called “lymphsarcoma” in approximately 5% of animals • Superficial lymph nodes • Heart • Stomach/intestine • Spinal canal • Reproductive tract

  4. Introduction • Diagnosis • Mainly blood/milk antibody tests (ELISA) • Also postmortem and with a test for the virus RNA (genetic material) • Control/eradication • The cornerstone in all programs is preventing blood cell movement • Needles, gloves, instruments, colostrum, insects??? • Test & slaughter/segregation/biosecurity measures • Herd conditions/goals dictate program

  5. Importance • BLV can be is economically significant • premature culling or death as a result of lymphosarcoma • The condemnation of carcasses at slaughter • Lower production & reproductive performance • Indirect losses: from export restrictions • Whole countries have eradicated • UK, Denmark, Netherlands, France….. • The prevalence in North America is increasing

  6. Historic prevalence of BLV in Canadaby province 63% 49% 16.6% 5.5% 1998-2003

  7. Current BLV project • Sponsored by 3 regional boards and AAFC (ADAPT/CAAP program) • Objectives: • Test ability of bulk tank milk ELISA to predict prevalence • Establish prevalence at herd level and estimate cow level • Pave the way for herd categorization/risk assessment/ management plan similar to AJDI

  8. Comparison of individual milk samples (gold standard) to Bulk tank milk

  9. General design: sampling rounds for all Maritimes dairy herds 641 634 628 Stratified random sampling of 90 based on BT ELISA values (5)

  10. Stratified random sampling Based on values of BT samples from the 5 groups Only Valacta herds <5, 5-40, 40-55, 55-70, >70

  11. Results from 85 herds • Manufacturers recommended cutoff of <5 = Neg • 6 herds with BT value<5 (BTM neg) in fact had a single positive low ELISA titre animal • All negative herds were correctly classified Relative * Sn: 91.8% * Sp: 100% At herd-level

  12. Prediction of within-herd prevalence by BT-values (modeling) Within –herd prevalence Correlation ~ 85% BT ELISA values

  13. ResultsBulk tank milk samples Prevalence at herd-level

  14. Overall herd prevalence • 623 herds tested 3X – 67 are <5 = negative (11%) • Can estimate within herd prevalence for the positive herds A E D BTM ELISA score and cow prevalence estimate A - < 5 = negative B - 5 to 40 = 10% C- 40-55 = 20% D - 55-70 = 40% E - >70 = 70% C B

  15. BLV take-home thoughts • BTM testing worked very well to determine status/predict level – unfortunately........ • Prevalence of BLV infection at herd and cow levels in the Maritimes has been increased over time  very high now • We need a practical control plan for BLV • Hence the title - Are We Up To The Challenge

  16. Atlantic Healthy Herds Johne’s Control AJDI BLV Control and Risk Management Web port - Data collection, delivery benchmarking BVD eradication and biosecurity Lameness Mgmt. and Benchmarking Calf Mgmt and colostrum assessment Internal parasite treatment model

  17. Atlantic Healthy Herds • Cost of these diseases is $10 M/year in Atlantic Canada • Support from the 4 regional boards • Seeking matching program funding • Phased rollout in beginning in 2014

  18. Thank you • Acknowledgements • Dairy Boards • ADAPT councils • NB Dept of Ag • Valacta • MQM technical team • Participating farmers