How foot and mouth disease is fought

The international Animal Health Code contains criteria for a country or zone to be listed as free from foot and mouth disease. There are free countries with and without vaccination. Free countries maintain their status by prohibiting or restricting the introduction of animals and animal products from countries where foot-and-mouth exists.

It is common for countries to put contingency plans into place to be prepared for an outbreak. Computer programmes have been developed to simulate possible outbreaks and to evaluate the economic effects of eradication by compulsory slaughter, vaccination, or different combinations of both methods.

Farming industry sources said the consequences of a wrong decision can be economically devastating. Countries with infected animals try to control the disease by eradication, vaccination or treatment.

Eradication programmes are favoured in countries with a low incidence of disease. Success depends on the thoroughness that is paid to the following:

* Immediate slaughter of all infected and suspicious cloven hoofed animals and those animals who had contact with them.
* Safe disposal of carcasses, for example in rendering plants where the complete carcasses can be autoclaved at temperatures above 121C.
* Restricted areas with a radius of three kilometres where all animal movement is strictly prohibited and even movement of humans is curtailed.
* Quarantine zones with a radius of 16 to 24 kilometres of the outbreak.
* Traffic through the quarantine zone is reduced to a minimum.
* Cleaning and decontamination of the premises.
* No possible contaminated material may leave the premises nor the quarantine zone.
* Burning of all contaminated objects that cannot be thoroughly disinfected.
* Restocking of the premises after 30 days with test animals which are monitored for clinical signs of the disease.
* Prohibiting or restricting the introduction of animals and animal products from countries in which foot-and-mouth exists.

Regular vaccination programmes in a form of blanket vaccination are favoured in countries with a high incidence of disease and where eradication does not seem possible quickly. The enormous number of animals saved from stamping out and the prevention of losses may outweigh the costs of the vaccination programmes.

In very rare cases and depending on the quality of the vaccine animals may suffer an adverse reaction to the vaccine and immunity can break down in individual animals. There is no cross immunity among the different strains of foot and mouth.

Treatment is prohibited in several countries because eradication programmes demand the slaughter of affected animals. Treatment must be avoided even in countries where it is not prohibited because treated animals shed high amounts of virus and are a very high risk for all remaining animals.

If allowed systemic antimicrobial drugs, mild disinfectants,immunomodulators and protective dressings are recommended to prevent secondary bacterial infection, alleviate the signs and strengthen the immune system.