Use of Vaccines in a BVDV Use of Vaccines in a BVDV Control/Eradication ProgramControl/Eradication Program

Steven R. Bolin, DVM, PhDDiagnostic Center for Population & Animal

HealthMichigan State University

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

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

Definitions

• Disease eradication – the permanent reduction of a disease’s 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

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?

Economic Considerations

•Cost-effectiveness analysis Comparison of the costs and effects of two

or more courses of actions

Most useful when expressed in health terms—how one disease compares with other diseases

Would herd health be better if disease A was controlled or if disease B was controlled—what would it cost to control disease A or to control disease B?

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 some—pharmaceutical & biologics companies, diagnostic laboratories, veterinarians

•Infrastructure decay

•Other health issues emerge

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)

BVD Control / Eradication Know cause of BVD

Good working knowledge of BVDV

Good working knowledge of BVDV interactions with the host—modes of transmission, duration of infection, duration of shedding, immune response

Effective interventions—biosecurity, vaccine, and environmental control—remove PI cattle

Practical, sensitive and specific diagnostic tests— serology, PCR, IHC, virus isolation

BVD Control / Eradication Cattle are essential for the life cycle of BVDVSufficient 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

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

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

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

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

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 animal’s life prevent disease and prevent transmission of BVDV – ? – 2 doses? 3 doses?

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?

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

Vaccination for BVDV in a Control Program—Year 6+

•Local—continue mixing vaccination with biosecurity and testing

•Regional—reassess prevalence of disease and agent, do what is needed

•National—reassess prevalence of disease and agent, implement enhanced measures in “trouble spots”

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

Vaccination for BVDV in an Eradication Program – year 6+

•Local—continue mixing vaccination with biosecurity and testing

•Regional—vaccination over except for the perimeter of the region (*maybe*), availability of live virus is controlled

•National—vaccination over, vaccines not available, laboratory strains of virus not available, serologic testing restricted to national lab, indemnification