Use of Vaccines in a BVDV Control/Eradication Program

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Use of Vaccines in a BVDV Control/Eradication
Program

• Steven R. Bolin, DVM, PhD
• Diagnostic Center for Population Animal Health
• Michigan State University

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Definitions

• Disease control programs designed to reduce
  disease incidence, prevalence, morbidity or
  mortality to a locally acceptable level as a
  result of deliberate efforts continued
  intervention measures are required to maintain
  the reduction MMWR 48 (SU01) 23-27, 1999
• Disease control prevent by any means
  transmission of disease from animal to animal

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Successful disease control requires thorough
knowledge of the causal agent and the disease
cycle, host pathogen interactions, environmental
factors, and cost. Encyclopedia Britannica
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Definitions

• Disease eradication the permanent reduction of
  a diseases prevalence in a geographic area to
  zero
• Indicators of eradicability keys to a possible
  successful outcome
• an effective intervention is available
• practical diagnostic tools exist that have the
  sensitivity and specificity to detect levels of
  infection that can lead to transmission
• cattle are essential for the life-cycle of the
  agent
• no other vertebrate host for the agent exists
• agent does not amplify in the environment

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Economic Considerations

• Resources are limited
• Resources cross sectors
• Time, personnel, equipment, physical facilities,
  money
• Are sufficient resources available to handle a
  disease control/eradication program?
• Are sufficient resources left over to handle
  other existing issues?

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Economic Considerations

• Cost-effectiveness analysis
• Comparison of the costs and effects of two or
  more courses of actions
• Most useful when expressed in health termshow
  one disease compares with other diseases
• Would herd health be better if disease A was
  controlled or if disease B was controlledwhat
  would it cost to control disease A or to control
  disease B?

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• Direct effects of a disease control/eradication
  program
• Disease becomes rare or ceases to exist control
  measures may change or cease
• Money is saved, herd health improves, market
  increases, value increases, profit increases
• Consequent effects
• Economic decline for somepharmaceutical
  biologics companies, diagnostic laboratories,
  veterinarians
• Infrastructure decay
• Other health issues emerge

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Social / Political Considerations

• Disease control, and especially disease
  eradication, depend on social and political
  commitment that likely must last for years
• Available resources seldom allow more than a very
  limited number of control/eradication programs to
  occur simultaneously
• Once the commitment is made to control a disease,
  failure to control or eradicate the disease will
  cause a loss of credibility for those who
  promoted the program (personal risk of failure)

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BVD Control / Eradication

• ? Know cause of BVD
• ? Good working knowledge of BVDV
• ? Good working knowledge of BVDV interactions
  with the hostmodes of transmission, duration of
  infection, duration of shedding, immune response
• ? Effective interventionsbiosecurity, vaccine,
  and environmental controlremove PI cattle
• ? Practical, sensitive and specific diagnostic
  tests serology, PCR, IHC, virus isolation

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BVD Control / Eradication

• ? Cattle are essential for the life cycle of BVDV
• Sufficient resources are available for a BVDV
  control / eradication program
• ? Local program
• ? Small regional program
• ? Large regional/national program
• Sufficient resources will be left over to handle
  other health issues
• BVDV is the most important/costly health problem
  for the cattle industry/for all animal health

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Vaccination In Disease Control

• Advantages of vaccination
• Considered the most cost effective means for
  control of infectious disease in livestock
• Rapid method for establishing the 80 herd
  immunity thought necessary for disease control
• Vaccination helps control the impact of events
  that you can not control wildlife reservoir,
  hole in the fence, out of control neighbor
• Testing helps control the impact from known risks
  introduction of new animals, going to fairs and
  shows

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Vaccination in Disease Eradication

• Advantages of vaccination
• Rapid means for establishing herd immunity
• Create zones of containment or create islands
  that are free of disease/free of agent
• Spares resources until they become critically
  needed at the end of an eradication program

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Vaccination in Disease Control/Eradication

• Disadvantages of vaccination
• May create a diagnostic dilemma with use of
  serology differentiate vaccinated from infected
  animals
• Faster, more effective method for disease control
  is ignored Stamp out method
• Production capacity for the vaccine may not be
  sufficient to meet the needs for vaccine usage
• 40,000,000 doses needed to get 80 coverage and
  production capacity is only 5,000,000 doses

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Vaccination in Disease Control/Eradication

• Is a vaccine available?
• Modified live-virus and inactivated-virus
  vaccines are available
• Multiple viral isolates and both major serologic
  groups of BVDV represented in the vaccines
• Are the vaccines effective?
• Prevent harmful clinical disease yes
• Prevent transmission of BVDV mostly

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Vaccination in Disease Control/Eradication

• Serologically differentiate vaccinated from
  infected animals in high throughput diagnostic
  testing no
• Production capacity sufficient to meet needs ?
• Resources available to administer vaccine ?
• Will one dose of vaccine administered only once
  in the animals life prevent disease and prevent
  transmission of BVDV ? 2 doses? 3 doses?

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Vaccination in Disease Control / Eradication of
BVDV

• Are there other effective means for eradication
  of BVDV that might use less resources maybe
• If we try to eradicate BVDV, and use vaccination
  as a primary tool, are we prepared to stop
  vaccinating and use stamp out?
• If we try to eradicate BVDV, and do not use
  vaccination, are we prepared to use stamp out?

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Vaccination for BVDV in a Control Program

• Local-mix vaccination with biosecurity and
  testing
• Regional - vaccinate at least 80 of animals in
  year one, only acquire vaccinated and tested
  animals
• Vaccinate at least 80 of all calves (100 of all
  replacements) every year for 5 years
• National - vaccinate at least 80 of animals
  within 2 years, only acquire vaccinated and
  tested animals
• Vaccinate at least 80 of all calves (100 of all
  replacements) every year for 5 years

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Vaccination for BVDV in a Control ProgramYear 6

• Localcontinue mixing vaccination with
  biosecurity and testing
• Regionalreassess prevalence of disease and
  agent, do what is needed
• Nationalreassess prevalence of disease and
  agent, implement enhanced measures in trouble
  spots

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Vaccination for BVDV in an Eradication Program

• Local mix vaccination with biosecurity and
  testing
• continued use of vaccination may be necessary to
  minimize effect of BVDV if it returns
• Regional comprehensive use of vaccination
  probably necessary at the start of the program
• perimeter vaccination may be necessary at the end
  of the program
• National vaccination required, vaccine
  selection will be limited, testing will be
  controlled

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Vaccination for BVDV in an Eradication Program
year 6

• Localcontinue mixing vaccination with
  biosecurity and testing
• Regionalvaccination over except for the
  perimeter of the region (maybe), availability
  of live virus is controlled
• Nationalvaccination over, vaccines not
  available, laboratory strains of virus not
  available, serologic testing restricted to
  national lab, indemnification

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