CASE NOTES

ROLE OF VACCINATION IN FOOT AND MOUTH DISEASE (FMD) CONTROL

Therese Wright, Biosecurity NSW

Posted Flock & Herd April 2013

Introduction

This article aims to provide a summary of the potential role of vaccination in FMD control in an Australian context.

POTENTIAL BENEFITS OF VACCINE IN FMD CONTROL

As vaccinated animals are less likely to be infected and, if they are infected can be expected to shed less virus, vaccination can be used to minimise spread of disease particularly in areas at high risk of rapid transmission or in an outbreak where there are insufficient resources for rapid destruction and disposal.

Vaccine could also be used to protect high value animals from infection, minimising the risk that studs or zoos become infected.

Public concern about animal welfare and environmental risks arising from the slaughter and disposal of FMD infected or at risk herds and flocks is likely to be high. FMD vaccination may minimise these public and/or political concerns by minimising the spread of infection and by providing an alternative to immediate slaughter and disposal. Flocks or herds that are confirmed to be infected despite vaccination could potentially move to designated abattoirs or knackeries for process slaughtering.

FMD VACCINES

The currently preferred vaccines for FMD control are inactivated vaccines that use an oil based adjuvant. The advantages of these vaccines include validated safety data sets and a relatively low unit cost.

New-generation subunit vaccines appear to be promising but, if developed, may initially be prohibitively expensive.

POTENTIAL ISSUES WITH USE OF VACCINE FOR FMD CONTROL

Vaccination is dependent on the availability of an appropriate vaccine that matches the outbreak strain. If the outbreak is not controlled quickly vaccinates will require a six monthly booster. In long outbreaks the virus may mutate sufficiently that the initial vaccine becomes less effective or ineffective and the match between the field and vaccine strains must be checked at regular intervals.

Ruminant vaccinates challenged after vaccination by live pathogenic viruses (of the same strains as in the vaccine) may become FMD carriers (cattle may remain carriers for two years or more and sheep for up to nine months), but the proportion of carriers is lower in vaccinated herds than convalescent non-vaccinated herds. Vaccination greatly reduces the quantity of virus able to be recovered from carrier vaccinates compared with convalescent unvaccinated cattle. No infection has been recorded of non-immune animals in contact with vaccinated carrier cattle.¹

Consumers may be concerned that products from vaccinated animals could pose a human health risk.

As with other vaccines with an oil based adjuvant, accidental self-injection with the vaccine can cause intense vascular spasm resulting in tissue necrosis. Any persons who accidently self injects vaccine must seek immediately expert surgical attention.

VACCINE BANK

Australia has contractual arrangements with Merial for the supply of antigen to be available for the production of FMD vaccines. This allows supply of 500,000 doses of a number of FMD strains within seven business days of notification. The nine antigens in the vaccine bank have been selected to provide broad coverage against potential FMD threats and are regularly reviewed.

If the use of vaccine is approved as part of the response, vaccine of the appropriate virus strain will be ordered as soon as the strain has been identified. Merial's experience in responding to outbreaks in other countries suggests that the vaccines could be delivered within five days of ordering.

A cold-chain distribution company has been contracted to clear the vaccine through customs, store vaccine at its cold store facility, distribute it as requested by Animal Health Australia and provide stock control. The company will also arrange for the return and destruction of unused vaccine doses.

The FMD Vaccine Bank is managed by Animal Health Australia through a project that is funded by the Commonwealth government, the eight State and Territory governments and affected national livestock industry associations including Australian Pork Limited, Cattle Council of Australia, Australian Dairy Farmers Limited, Australian Lot Feeder's Association, Sheepmeat Council of Australia, NFF on behalf of Woolproducers and the Goat Industry Council of Australia.

NATIONAL POLICY

The Standing Council on Primary Industries agreed at the meeting of April 27 2012 to adopt a national policy statement that provides for vaccination to be considered as a potential control tool from day one of an emergency response to FMD.

Australia's response policy for FMD is to contain and eradicate disease as rapidly as possible. Vaccination may be considered if:

the disease spreads beyond the limit of available resources to contain it,
to protect large animal concentrations and
to limit infection and minimise virus excretion.

Vaccines will only be used, with the approval of the Consultative Committee on Emergency Animal Diseases (CCEAD) and the National Management Group (NMG), in accordance with permits issued by AQIS and the Australian Pesticides and Veterinary Medicines Authority.

For eradication purposes, vaccination can be used in different ways:

If destruction and disposal of infected animals or suspects are likely to be delayed for more than 48 hours or there is a high risk of disease spread into surrounding concentrated populations, vaccine may be applied within known infected areas ('suppressive' vaccination).
Vaccination can be applied outside infected areas to protect animals from infection ('protective' vaccination) - for example, surrounding an infected area to create a barrier of immune animals between the infected and uninfected areas ('ring' vaccination), or to protect specific high-value or rare groups in uninfected areas ('targeted' vaccination).
Mass ('blanket') vaccination can be applied to large numbers of animals if disease spread is significant.

VACCINE PROCEDURES

National Standard Operating Procedures² relating to FMD vaccination have been developed and include:

www.animalhealthaustralia.com.au Ordering of FMD vaccine and distribution to states and territories

www.animalhealthaustralia.com.au Control of FMD vaccine at a designated vaccination centre

www.animalhealthaustralia.com.au Assessing and inspecting a property prior to admin FMD vaccine and

www.animalhealthaustralia.com.au Vaccinating livestock on a property for FMD.

POLICY ISSUES THAT REQUIRE CLARIFICATION

Although it has been agreed that vaccine may be used, a number of policy issues around FMD vaccination are still under discussion or would be decided on the basis of the particular circumstances of the outbreak. These issues include:

who would administer the vaccine (e.g. producers versus vaccination teams) and must a veterinarian supervise vaccination,
what species should be vaccinated,
what is the fate of vaccinates (e.g. live out normal life or slaughtered prior to proof of freedom declaration).

Animal Health Committee has convened a Vaccination Expert Advisory Group to develop decision support tools that will address many of these issues.

FMD VACCINE RESEARCH PROJECT

Staff from the Australian Animal Health Laboratory at Geelong leading a five year FMD risk management project. The objectives of the project are to

Generate species specific data on vaccine efficacy,
Investigate disease behaviour in Australian animals,
Generate input data for disease models,
Improve laboratory diagnostic capability, validate diagnostic assays and generate and keep bulk reagents,
Gain experience in working with live FMD virus,
Improve knowledge on the molecular epidemiology of FMD in SE Asia, and
Provide sound technical advice to feed into disease control plans.

The project will include work to:

Test vaccine efficacy against using antigens in the Australian vaccine bank on cattle in Argentina, sheep in South Africa and pigs in Vietnam.
Validate Point of Care (POC) testing devices
Further molecular epidemiology of FMD in SE Asia, and
Build capacity in Vietnam and Thailand.

It is anticipated that this work will assist Australia and SE Asian neighbours to make informed decision on vaccine strains, improve the design of control strategies and provide technically sound advice on the use of POC devices during outbreaks and surveillance.

Acknowledgements

Information on the FMD research project is derived from W. Vosloo's presentation to the FMD roundtable on 17 September 2012.

References

AVPMA Permit 11606 to allow emergency use and supply of an unregistered agvet chemical product at: permits.apvma.gov.au as 21 December 2012
www.animalhealthaustralia.com.au as 21 December 2012