Foot and mouth disease (FMD) is a severe and highly contagious viral disease of livestock. It has a significant economic impact on livestock, thereby disrupting regional and international trade in animals and animal products. The disease affects cattle, swine, sheep, goats and other cloven-hoofed ruminants.
Animals that are intensively reared are more susceptible to the disease than traditional breeds. The disease is rarely fatal in adult animals, but there is often high mortality in young animals due to myocarditis or, when the dam is infected by the disease.
FMD is characterised by fever and blister-like sores on the tongue and lips, in the mouth, on the teats and between the hooves. The disease causes severe production losses, and while the majority of affected animals recover, the disease often leaves them weakened and debilitated.
The organism which causes FMD is an aphthovirus of the family Picornaviridae. There are seven strains (A, O, C, SAT1, SAT2, SAT3, and Asia1) which are endemic in different countries worldwide. Each strain requires a specific vaccine to provide immunity to a vaccinated animal. (Kahn et al. 2005)
TRANSMISSION AND SPREAD:
FMD is found in all excretions and secretions from infected animals. Notably, these animals breathe out a large amount of aerosolised virus, which can infect other animals via the respiratory or oral routes.
The virus may be present in milk and semen for up to 4 days before the animal shows clinical signs of disease.
The significance of FMD is related to the ease with which the virus can spread through any or all of the following
- Infected animals newly introduced into a herd (carrying virus in their saliva, milk, semen, etc.);
- Contaminated pens/buildings or contaminated animal transport vehicles;
- Contaminated materials such as hay, feed, water, milk or biologics;
- Contaminated clothing, footwear, or equipment;
- Virus-infected meat or other contaminated animal products (if fed to animals when raw or improperly cooked);
- Infected aerosols (spread of virus from an infected property via air currents).
Animals that have recovered from infection may sometimes carry the virus and initiate new outbreaks of the disease.
The severity of clinical signs will depend on the strain of virus, the exposure dose, the age and species of animal and the host immunity. Morbidity can reach 100% in susceptible populations.
Mortality is generally low in adult animals (1–5%), but higher in young calves, lambs and piglets (20%or higher). The incubation period is 2–14 days.
Clinical signs can range from mild or inapparent to severe: they are more severe in cattle and intensively reared pigs than in sheep and goats.
The typical clinical sign is the occurrence of blisters (or vesicles) on the nose, tongue or lips, inside the oral cavity, between the toes, above the hooves, on the teats and at pressure points on the skin.
Ruptured blisters can result in extreme lameness and reluctance to move or eat. Usually, blisters heal within 7 days (sometimes longer), but complications, such as secondary bacterial infection of open blisters, can also occur.
TREATMENT, PREVENTION AND CONTROL
There is no specific treatment for FMD. The conventional method of treating infected animals mainly involves the use of antibiotics, flunixin meglumine and mild disinfectants.
FMD has been managed traditionally by use of natural soda ash solution for washing of the lesions and other communities have applied honey and even finger millet flour to the lesions
Measures that are recommended at the farm level include:
- control over people’s access to livestock and equipment;
- controlled introduction of new animals into existing herds;
- regular cleaning and disinfection of livestock pens, buildings, vehicles and equipment;
- monitoring and reporting of illness;
- Appropriate disposal of manure and dead carcasses