Bovine Viral Diarrhea Virus in an Embryo Transfer Recipient Heifer

1. Bovine Viral Diarrhea Virus in an Embryo Transfer Recipient Heifer Kristin Bloink and Alissa McCormick VIPS V

2. Background: • Michigan Hereford seedstock operation purchased 12 embryos • Private embryo transfer company collected and transferred 6 of the embryos into healthy recipient heifers • Heifers were shipped to the producer after pregnancies were confirmed

3. Farm Timeline: • October, 2000: Immediate introduction of the 6 recipient heifers into the 55 head herd • By January, 2001: Abortions in 3 recipient heifers and 4 established herd heifers (all 4-8 months gestation)

4. Initial evaluation: • Walk through of operation completed • No obvious sick animals identified • Appropriate facilities, feed quality, nutrition program, and manure handling

5. Differential Diagnosis: • Bovine viral diarrhea virus (BVDV) • Infectious bovine rhinotracheitis (IBR) • Leptospirosis • Neospora caninum • Moldy feed exposure • Brucella abortus • Haemophilus somnus • Listeria monocytogenes • Congenital abnormalities

6. Narrowing the field of possibilities: • Most likely BVDV, IBR, Leptospirosis, or Neospora based on: • case history • herd history • prevalence of Michigan cattle diseases • Moldy feed, Brucella abortus, Haemophilus somnus, Listeria monocytogenes, and congenital abnormalities felt to be less likely

7. Laboratory evaluation: • Necropsies were done on aborted fetuses to include: • Gross evaluation of organs • Histopathologic evaluation: FA – lung, liver, spleen, kidney, thymus • Bacteriologic evaluation: VI – kidney, liver, lung, spleen

8. BVDV was isolated from one aborted fetus Necropsy results:

9. All embryo transfer heifers and 25 other cows from the herd were tested for BVDV by virus isolation Herd testing:

10. A pregnant embryo transfer heifer (#485) was found positive for BVDV and later confirmed to be persistently infected (PI) with a type 2 virus Herd testing results:

11. Management recommendations: • Cull embryo transfer heifer #485 from the herd • Consider changing vaccination program to include BVDV vaccines that cover both type 1 and type 2 viruses • Screen all calves for BVDV in the spring (2001)

12. Farm timeline: • #485 is culled from the herd sacrificing the fetus • The farm vaccination program for BVDV continues without modification: Type 1 MLV prior to breeding Type 1 Killed vaccine in the fall • All calves screened in the spring of 2001 using whole blood samples

13. Farm timeline: • Fall 2001: MSU consulted again by the producer after experiencing 2 abortions, the death of a 2 day old calf, and a higher rate of open cows • Repeat screening in the fall of 2001 on all calves due to possible inaccuracies with the spring screening • Skin samples (ear notch) used • Serology also performed on all unvaccinated calves to detect recent exposure to BVDV

14. BVDV screening options: • Serum sample (red top) pre colostrum or after 4 months of age (~$6/sample) • Whole blood sample (purple top) after colostrum but before 4 months of age (~$15-20/sample) • Skin sample (ear notch) anytime (~$12/slide - 5 samples per slide) Grooms DL and ED Keilen. 2002. Screening of neonatal calves for persistent infection with BVDV by immunohistochemistry on skin biopsy samples. Clin Diagn Lab Imm 9:898-900.

15. The ongoing problem: • 2 calves were found to be positive for BVDV by skin testing and later confirmed to be persistently infected • All of the unvaccinated calves sampled had titers >1:256 to type 2 BVDV

16. Interpretation of results: • High titers in the unvaccinated calves indicated recent exposure to BVDV • Circulating virus was a type 2 BVDV virus Pillars RB and DL Grooms. 2002. Serologic evaluation of five unvaccinated heifers to detect herds that have cattle persistently infected with bovine viral diarrhea virus. AJVR. 63:499-505.

17. Important BVDV facts: • RNA virus from the genus Pestivirus, family Flaviviridae (related to Border Disease, Hog Cholera) • Antigenic variation between isolates yields a type 1 “classical” form and a type 2 form

18. Important BVDV facts: • Unstable at low and high pH and at high temperature • Does not persist in the environment typically beyond 2 weeks • Susceptible to chlorhexadine, phenol, iodophores, aldehydes, and hypochlorates Smith. 2002. Textbook of large animal medicine. P707.

19. Sheep Pigs Mucosal Disease Deer? Thrombocytopenia Normal Acute Infection Acute Death Poor Performance Immunosuppression Immunosuppression Acute Diarrhea Fetal Infection SubclinicalInfection Abortions Persistent Infection Normal Congenital Defects “Weak Calf” Syndrome

20. Factors determining clinical disease status: • BVDV immune status • Pregnancy status • Gestational age of the fetus • Level of environmental stress

21. BVDV and pregnancy: • BVDV crosses the placenta with ease in naïve animals • Outcome of intrauterine infections with BVDV is determined by the time of fetal infection, the properties of the virus biotype and its pathogenic potential

22. Outcomes of BVDV in pregnancy: • Fertilization failure • Early embryonic death • Fetal abortion and mummification • Congenital defects • May see many different anomalies but cerebellar hypoplasia is most common • Immunotolerance to BVDV • Normal but seropositive to BVDV

23. Cerebellar hypoplasia:

24. Outcomes of BVDV in pregnancy: • Fertilization failure • Early embryonic death • Fetal abortion and mummification • Congenital defects • May see many different anomalies but cerebellar hypoplasia is most common • Immunotolerance to BVDV • Normal but seropositive to BVDV

25. Shed large amounts of virus entire life via nasal secretions, saliva, semen, urine, feces, tears, and milk #1 source of BVDV to a herd Role of the PI animal:

26. The PI role in the index case: • One of the embryo transfer recipient heifers (#485) was a PI animal • She constantly shed type 2 BVDV virus which infected other herd members • Caused abortions • Led to the development of PI calves

27. History of Embryo Transfer: • 1890: Transfer of rabbit embryos showed there was no genetic influence on the offspring by the recipient • 1930: Collection of first bovine embryo • 1951: First successful bovine embryo transfer

28. Superovulation of donor cow:

29. Artificial insemination of donor cow:

30. Recovery of embryos:

31. Isolation and classification of embryos:

32. Storage of embryos:

33. Transfer of embryos into recipients:

34. Confirmation of pregnancy:

35. Learning issues from this case: • Importance of herd biosecurity • Understanding the cross protective limitations of current BVDV vaccines

36. Herd biosecurity recommendations: • Adequate health history on animals added to a herd • ET recipients should be vaccinated for Brucellosis, IBR, BVDV, Bovine Respiratory Syncytial Virus, Parainfluenza 3, Leptospirosis (5 way) and Clostridia (7 way), and treated with a broad anti-parasitic (International Embryo Transfer Society, 2002 Manual) • Isolation of new animals added to a herd for 2-3 weeks • Screening of new animals for BVDV PI

37. BVDV vaccines limitations: • Type 1 BVDV vaccines may only provide about 60% protection against a type 2 challenge Brock KV and VS Cortese. 2001. Experimental fetal challenge using type 2 BVDV in cattle vaccinated with MLV vaccine. Vet Therapeutics 2:354-360.

38. Thank you: Dr. Dan Grooms Dr. Paul Coe