Title: BVD Vaccines (11/94)
Document-date: November 1994
Author: Rick Hill
Posting-date:
BVD VACCINES - VERSION 2.0
General considerations
Continuing reports of outbreaks of severe BVD have raised questions aboutprotection offered by currently available BVD vaccines. Early informationon the nature and extend of severe BVD complicated the already difficult task of devising bovine vaccination programs (are the objectives of vaccination to prevent fetal infection through vaccination of breeding stock, prevent clinical disease, provide protection following outbreaks, or all of these?).
As we learn more about this important bovine viral pathogen, knowledge of
the types and availability of currently licensed vaccines will undoubtedly be
essential in designing vaccination programs against the severe form of the
disease.
Types of vaccines:
Modified live virus versus killed virus vaccines
Two types of BVD vaccines are currently available: modified live virus (MLV)
vaccines and killed virus (KV) [or inactivated] vaccines. Modified live
virus vaccines contain viruses that have been altered (attenuated) in such a
way that they have reduced virulence, yet retain their antigenic properties and
induce a protective response. MLV vaccines must replicate after
inoculation to produce enough antigen to produce an immune response.
Killed virus vaccines contain viruses that have been treated by chemical or
physical means to prevent them from replicating in the
vaccinate. There are some general advantages and disadvantages for
each of these types of vaccines:
|
Modified live virus vaccines
|
|
|
Advantages |
Disadvantages |
|
--One dose required |
--Possible reversion to virulence |
|
--Quicker immune response |
--Possible viral shedding |
|
--Stronger & more durable response |
--Not recommended for pregnant animals or animals in contact with pregnant animlas. |
|
--Fewer post-vaccinal reactions |
--Improper handling may inactivate (example: must be used quickly following rehydration) |
Additional disadvantages that have been associated with MLV BVD vaccines in
particular include immunosuppression and induced
disease in some immunologically tolerant animals.
Killed virus vaccines
Advantages
Disadvantages
--Safe - no possibility for
reversion
--Multiple doses required
--Recommended for pregnant
animals --Adjuvants may potentiate response
--Stable in
storage
--Weaker immune response
--Shorter duration immune response
--Adjuvants may cause reactions
--Hypersensitivity reactions more common
General vaccination recommendations
Vaccination is an important part of any preventative medicine program, but decisions regarding specific vaccination recommendations are often difficult on geographic area, herd size, health history, existing disease conditions, risk of exposure, individual management practices, etc. A wide diversity of opinions exists on the best vaccination protocol. Greater controversy exists over vaccination procedures under outbreak conditions. Designing and recommending immunizing programs can be a challenge that requires a considerable amount of professional judgment. Making sound recommendations on usages requires a strong medical and scientific background including (but not limited to) knowledge of the biology and epidemiology of the infectious agent, knowledge of the safety and efficacy of the vaccines (including a critical assessment of the manufacturers claims), review of the literature, assessment of the needs of animal owners, and personal and collective experience. Recommended BVD vaccination protocols are available in several publications (AVMA Council Report, 1993; Ames and Baker, 1990; Hjerpe, 1990; Schultz, 1994). Veterinarians have a professional obligation to educate themselves and their clients on the currently accepted vaccination practices. Animalvowners are encouraged to consult their veterinarian when designing preventative animal health programs.
Current vaccines and severe disease
The eminent concern for cattle owners with currently available BVD vaccines
is whether the immune response generated by the vaccine virus is sufficient to
protect against challenge from field isolates (both Type 1 and Type 2 BVD
viruses). While there is considerable evidence that currently available
vaccines are protective
against challenge with Type 1 viruses, it is unknown whether curently available vaccines are equally protective against
the Type 2 viruses. Current epidemiological evidence suggests that
current vaccines are partially protective. Properly vaccinated herds do
not experience the high morbidity and mortality seen in unvaccinated
herds, yet at the same time it appears that abortions occur in exposed animals
and the fetus is not protected. Further studies are necessary to examine cross
protection between the Type 1 and Type 2 viruses, or whether antigen levels and
adjuvants affect the broadness of immunity against
challenge with mismatched strains. Until these data become available, it
is important to remember that BVD virus is a major problem in the bovine
population regardless of genotype.
Availability of vaccines
BVD vaccines are currently available as monovalent
vaccines and in multivalent preparations with three other important bovine
viral pathogens (infectious bovine rhinotracheitis
virus, parainfluenza-3 virus, and bovine respiratory syncytial
virus) and a variety of inactivated bacterial pathogens. The following
companies
are currently licensed to produce BVD vaccines in the
Ballistivet, Inc., (800) 654-4072
Biocor, Inc., (800) 258-8779
Boehringer Ingelheim Animal
Health Inc., (800) 821-7476
Colorado Serum Company, (800) 525-2065
Coopers Animal Health, Inc., (800) 541-7459
Diamond Scientific, (800) 255-6517
Fort Dodge Laboratories, Inc., (800) 477-1365
Grand Laboratories Inc., (800) 843-3386
Langford Laboratories, Inc., (800) 426-2924
Miles, Inc., (800) 255-6517
Sanofi Animal Health, Inc., (800) 538-2382
Smithkline Beecham Animal Health, (800) 366-5288
Proper use of vaccines
Perhaps the most important consideration when considering the performance of vaccines is proper administration. Improper mixing, delays in use following rehydration, and improper use of disinfectants in syringes, and not following label vaccination schedules are common causes for product failure. All users are encouraged to read and follow all label and insert directions and consider the objectives of the vaccination program.
References
AVMA Council Report, 1993. Bovine immunization guidelines. J. Am. Vet. Med. Assoc., 203:238-242.
Ridpath, J.F., Bolin, S.R., and Dubovi, E.J., In Press. Segregation of bovine viral diarrhea virus into genotypes. Virology.
Schultz, R.D., 1994. Certain factors to consider
when designing a bovine vaccination program. Proceedings
Twenty Sixth Annual Convention AABP. pp. 19-26.
For more information, please contact:
Centers for Epidemiology and Animal Health
APHIS:VS:CEAH, ATTN: NAHMS
Fort Collins, CO 80526-8117
(970) 494-7000