Use of Vaccines in a BVDV Control/Eradication Program Steven R. Bolin, DVM, PhD Diagnostic Center for Population & Animal Health Michigan 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 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

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