Foot and mouth disease (FMD) is a severe, highly contagious viral disease of cattle and swine. It also affects sheep, goats, deer, and other cloven-hooved ruminants. Foot and Mouth Disease is not recognised as a zoonotic disease. The disease spreads very quickly if not controlled and because of this is a reportable disease.

The disease is caused by a virus of which there are seven ‘types’, each producing the same symptoms, and distinguishable only in the laboratory. Immunity to one type does not protect an animal against other types. The interval between exposure to infection and the appearance of symptoms varies between twenty-four hours and ten days, or even longer. The average time, under natural conditions, is three to six days.

The virus survives in lymph nodes and bone marrow at neutral pH, but is destroyed in muscle when pH is less than 6.0, i.e., after rigor mortis. The virus can persist in contaminated fodder and the environment for up to one month, depending on the temperature and pH conditions. Airborne spread of the disease can take place and under favourable weather conditions the disease may be spread considerable distances by this route. Animals pick up the virus either by direct contact with an infected animal or by contact with foodstuffs or other things which have been contaminated by such an animal, or by eating or coming into contact with some part of an infected carcase.

Outbreaks have been linked with the importation of infected meat and meat products. The disease can also be spread by people, vehicles and other objects that have been contaminated by the virus.

SYMPTOMS

Cattle typically show more severe disease than other animals. The incubation period is 2-10 days. Initially, one or two cattle present with fever (>40.0°C), depression, loss of appetite, marked drop in milk yield and salivation. When housed or closely confined, other cattle in the group will show clinical signs over the next 24-48 hours and such spread is dramatic.

Vesicles (fluid filled blisters) on the tongue, dental pad and hard palate quickly rupture leaving shallow ulceration with shreds of mucosa at the periphery. The underlying tissues are reddened and painful. There are no ocular or nasal discharges. During the acute phase of disease, there is marked weight loss and milk yield reduction. Foot lesions often become secondarily infected and animals are very lame and often may be reluctant to rise. The ulcers start to heal by around day 10 after infection but recovery takes several more weeks, during which time the animal will have a great deal of condition.

The clinical signs in other species are less severe with sheep, goats and deer often presenting with a fever and lameness with vesicles only seen on close inspection.

• Fever

• Bilsters in the mouth and on feet

• Drop in milk production

• Weight loss • Loss of appetite

• Quivering lips and frothing of mouth

• Cows may develop blisters on teats

• Lameness

TREATMENT

There is no specific treatment for Foot and Mouth Disease. In endemic countries antibiotic therapy may be used to control secondary bacterial infection of ulcers but recovery takes several weeks to months.

PREVENTION

Foot and Mouth Disease is one of the most difficult animal infections to control. Because the disease occurs in many parts of the world, there is always a chance of its accidental introduction into an unaffected country. Export restrictions are often imposed on countries with known outbreaks. Foot and mouth disease outbreaks are usually controlled by quarantines and movement restrictions, euthanasia of affected and in-contact animals, and cleansing and disinfection of affected premises, equipment and vehicles.

Infected carcasses must be disposed of safely by incineration, rendering, burial or other techniques. Milk from infected cows can be inactivated by heating to 100°C (212°F) for more than 20 minutes. Slurry can be heated to 67°C (153°F) for three minutes. Rodents and other vectors may be killed to prevent them from mechanically disseminating the virus. Good biosecurity measures should be practiced on uninfected farms to prevent entry of the virus.