Back to Vaccination
From the Powerpoint presentation of Dr Paul Sutmoller at the government's Royal Society Inquiry "Vaccination" meeting on January 15th 2002
What makes sense for prevention, control and eradication of FMD?
How to get rid of the disease soonest?
How can we minimize impact on animal production and welfare?
How can we limit the damage to the rural society as a whole?
Long-term ban on free international trade of vaccinated animals
Arguments ( Note added Oct 07 - ie flawed arguments used which need to be challenged - as was made clear by the commentary from Dr Sutmoller):
* Convalescent or sub-clinical infected animals, become FMD virus carriers.
* Vaccinated animals have antibodies against FMD and that this obscures the tracing of the disease.
* (One cannot eat meat from vaccinated animal)
Risk of vaccinated animals
* Just how large is that risk of creating vaccinated carriers and what would be the risk posed by such animals?
* Does that risk justify the assumed zero-risk approach of "stamping-out" or, when vaccination is used, the killing of the healthy vaccinated livestock?
* Could the risk of infected animals in vaccinated populations be managed effectively by the use of modern diagnostic methodologies?
* Is stamping-out to the bitter end really assuring zero risk?
Questions to be answered
* Once the disease is brought under control what should be required to get a FMD-free status back?
* What did we learn from the recent experiences?
* Are the current international rules still adequate?
* What are the risks of (re-) introduction of FMD?
* What are the risks of international trade, tourism, swill feeding, FMD-laboratories and vaccine plants, and terrorist actions?
* How can these risks be mitigated and managed?
* stamping-out of infected farms and direct potential contagious contacts;
* stamping-out of infected farms plus ring (circle) culling;
* stamping-out of infected farms plus ring or area vaccination followed by slaughter of all vaccinated animals ("suppressive" vaccination);
* stamping-out of infected farms plus ring or area vaccination ("protective" vaccination);
* ring vaccination only without stamping-out of infected farms and slaughter of vaccinated animals
* strategic or general vaccination.
Some risks of stamping-out
* Heavy equipment used in these operations is difficult to decontaminate and might be a source of infection or contamination of roads when being driven to another job or back home.
* Disposal of cadavers presents a risk since virus in lesions, excrements and excretions is not rapidly destroyed after death and is disseminated by transport of cadavers, by pyres, at burial sites or digester plants.
* Transport systems for carcasses are not bio-secure, neither is the handling of the carcasses at the rendering plants.
* Large numbers of contractors not trained in disease containment become heavily contaminated.
* Intensive, active surveillance represents a risk.
Ring- (circle) culling
* "circle culling" and culling of contiguous farms were applied in the UK and in the Netherlands as an extension of usual stamping-out procedures.
* The circle represents a "fire break" around the outbreak.
* The diameter of the circle was based on the analysis of spread of FMD during the outbreak using computer models.
* The calculated distance of spread probably is due largely to the culling process itself as an additional risk of spreading the disease.
* Circle culling reduces the need for surveillance, but it creates potentially much higher numbers of cadavers, some of which might be infected.
Disadvantages of Ring- (circle) culling
* Most culled farms within the circle are not infected and, therefore, are culled without necessity.
* The operation itself has a high risk of disseminating FMD virus over short and long distances.
* A long drawn-out campaign is very disruptive for the rural society as a whole.
* The consequent application of circle culling (and of contiguous culls) is a threat to zoological collections and valuable (rare) breeding stock.
* Massive killing and destruction of livestock usually is not done with adequate respect for animal welfare.
* The small risk represented by hobby farms and small-holdings is not taken into account.
* Many culls represent a human tragedy and traumatic experience Ring- (circle) culling must be based on the evaluation of how virus spreads, and not be determined by mathematical circles.
The principal routes of virus spread to be considered are:
* animal movements from the farm, during the pre-clinical phase;
* wind, usually for a limited distance;
* vehicles (e.g. animal transport, machinery) contaminating roads that are used by the farmer's family and associates;
* contaminated vehicle from companies serving the farm;
* people (veterinarians, inseminators, visiting farmers, cleaning and disinfecting crews, etc.)
should be included in any contingency plan:
* to avoid all disadvantages of the massive killing and destruction of infected and healthy animals;
* to stop the disease from spreading;
* to prevent to the maximum extent possible the suffering of animals;
* to ascertain that a few week after vaccination life in the affected area can resume its normal course, with minimal socio-economic consequences
The logistics of a vaccination campaign are rather simple.
* It can be carried out on a large scale by a limited number of (trained) staff under full bio-safety conditions
* by farmers and trained farm hands as is common practice in South America (no risk of cross-contamination between farms because of people movements).
If FMD occurs in a previously FMD free country or zone without vaccination:
* If no vaccination is used to control an outbreak and stamping-out and serological surveillance are applied, the FMD free status can be regained and normal trade resumed 3 months after the last case;
* If stamping-out and emergency ("suppressive") vaccination are applied the waiting period is 3 months after the last vaccinated animal is slaughtered. A serological surveillance in the zone around the vaccination zone must demonstrate freedom from FMD.
If FMD occurs in a FMD free country or zone where vaccination is practised:
* If vaccination is used and stamping-out is applied, it takes 12 month after the last case to obtain the FMD free status;
* If vaccination is used, without stamping-out, it takes 24 month after the last case to obtain the FMD free status.
These trade regulations are not based on risk assessments, but rather:
* on the notion that vaccination might perpetuate carriers in the population that those carriers may pose a risk for FMD free countries that do not practise vaccination.
* that there are no methods available for the detection of carriers in vaccinated populations.
Normal export should be resumed, when after any outbreak, the veterinary services would show the absence of FMD
* This should be independent of whether stamping-out, stamping-out plus ring vaccination or vaccination only was used to control the outbreak.
* There should not be a set time limit.
* The sooner the country or region shows the absence of viral activity the earlier normal trade can be resumed.
Trade in live animals
* The current export of live animals practised from countries that do not practise vaccination has proven to be not risk-free.
* The international movement of vaccinated animals is restricted due to perceived risk of persistently infected animals.
* Under an adequate protocol the risk posed by the import of vaccinated animals is negligible.
True or false?
* "FMD free without vaccination" is risk free.
* "FMD free without vaccination" is not risk free.
* "FMD free with vaccination" is risk free.
* "FMD free with vaccination" is not risk free.
Meat and meat products from vaccinated cattle
* Negligible risk when slaughtered and processed under GMP and according to OIE regulations.
* Disease surveillance, control of the source cattle and slaughterhouse inspections are the main risk reduction measures.
* The risk reduction by maturation and deboning is probably over-emphasized.
* The fear of mechanical contamination of cattle carcasses with 'carrier virus' from the pharyngeal area during slaughter and processing is unfounded.
Milk and milk products from vaccinated cows
Risk assessments show that:
* Importation from countries with a high level of herd immunity, pose a close to zero or negligible risk.
* The importation of bovine embryos from vaccinated cows poses a negligible risk.
* The risk of the importation of semen from vaccinated bulls is negligible, with an adequate test protocol and when collected at collection centers, approved for semen export.
Vaccination and carriers
* Vaccination by itself cannot cause the carrier status (FMD vaccine is prepared with an inactivated antigen). A vaccinated animal must be exposed to active FMD virus to become a carrier.
* Vaccination suppresses or eliminates the amount of FMD virus (released or discharged) in the environment (low morbidity!) which makes it unlikely that carriers will be induced in vaccinated herds.
* Carriers among vaccinated cattle have not caused FMD outbreaks among susceptible non-vaccinated livestock populations like young cattle, sheep and pigs, nor have they hampered FMD eradication efforts.
Carriers or persistently infected animals
* Researchers have been unable to show that carriers cattle transmit FMD to susceptible contacts
* All experimental evidence of FMD virus transmission by carrier sheep is negative
* Pigs do not become carriers
* Vaccinated cattle or sheep exposed to FMD virus have a much smaller chance of becoming a carrier than susceptibles exposed to FMD virus
* "Vaccinated" carriers were no problem during the FMD eradication by vaccination in South America
Carriers or persistently infected animals
* The fear that vaccination causes FMD carriers and interferes with the eradication effort is completely hypothetical and scientifically unfounded
* There is much more chance of getting FMD carriers among cattle and sheep with clinical or subclinical FMD