[ Takam Yani ]
Foot and mouth disease (FMD) also known as apthous fever, is a very contagious viral disease caused by an epitheliotropic enterovirus of the picorna virus group, occurring in all cloven-footed animals. It is a OIE List A disease. It is a transboundary disease which greatly affects the production of livestock and disrupts regional and international trade of animals and animal products. Cattle and pigs are mostly affected, while sheep and goat less affected and wild ruminants like deer, antelope, etc, can also be affected. Horses cannot be infected, while camel, laboratory animals and humans are susceptible.
There are seven serotypes of the virus termed: O, A, C, ASIA1 and SAT (South African territories) 1, 2 and 3. Further diversity is found between strains within each serotype. The prevalent serotypes in India are O, A, and ASIA1. FMD is characterized by fever and vesicles in the mouth and on the muzzle, teat, and feet of animals, and is spread through contact with infected animals or their excretion. The virus can also be transmitted as an aerosol and through milk, semen, and ingestion of feed from infected animals (meat, offal). In a susceptible population morbidity can reach upto 100%, but with rare fatalities,except in case of young animals.
FMD is an economically important disease and is spread worldwide but has been eradicated from some regions, including Europe and North America. It is endemic in countries of Africa, South Asia and the Middle East.
Clinical signs and symptoms
The disease starts with a high fever (104°F to 106°F) accompanied by anorexia, depression and fall in milk yield.On formation of vesicles in mouth, the temperature falls.These vesicles rupture due to movement of jaw and tongue,leaving angry ulcers with ragged and irregular edges. There is plentiful salivation and the animal makes smacking noises. The saliva dribbles in strings from the mouth. There is also vesicles formation on the cleft of foot and these on rupture leaves red sores, which being painful renders the animal lame. On secondary bacterial invasion or infection by maggots the wound becomes deep and complicated,taking a longer time to heal. Appearance of the vesicles on the teat, especially at the orifice, is attendant with risk of mastitis due to secondary bacterial infection of the mammary gland.
Abortion may occur in pregnant animal and infertility may result. Animal loss condition rapidly and becomes emaciated. Because of affection of endocrine glands, recovered animals develop a dry and rough coat with long hairs, and such animals become ‘panters’, commonly occurring in crossbreed and exotic animals.
The incubation period of the virus is variable and depends on host, environment, route of infection and the strain of virus. The convalescence period is long for the virus. FMD should be differentiated from other similar diseases like vesicular stomatitis, vesicular exanthema, rinderpest, and mucosal disease.
Treatment, control and prevention
No particular treatment is available for the infected animals, but supportive care to be given in endemic areas.
In the regions that are normally FMD-free, control of the disease is typically attempted by culling all animals on infected premises, and animal movement controls are imposed to reduce the risk of virus spread.
In both normally FMD-free regions and endemic areas, vaccination around outbreaks may be used to limit the spread of the disease.
Control of FMD can be successfully achieved with good veterinary services, enabling rapid diagnosis and implementation of control measures, including, in some circumstances, the use of vaccine.
A progressive controlling pathway (PCP) has been developed by the FAO and adopted by the OIE to assist and facilitate those countries where FMD is still endemic to progressively reduce the impact of FMD and load of FMD virus. FMD-PCP is a 5 stage process:
Stage 1 focuses mainly on gaining an understanding of the epidemiology of FMD in the country and developing a risk-based approach to reduce the impact.
Stage 2 focuses on implementing risk-based control measures, such that the impact of FMD is reduced in one or more livestock sectors and/or in one or more zones.
Stage 3 focuses on progressive reduction in outbreak incidence, followed by elimination of FMD virus circulation in domestic animals in at least one zone of the country.
Stage 4 focuses on maintaining ‘zero tolerance’ of FMD within the country/zone and eventually achieving OIE recognition of ‘FMD-free with vaccination’.
Stage 5 focuses on maintaining ‘zero incidence’ of FMD within the country/zone and ultimately achieve OIE recognition of ‘FMD free without vaccination’.
Strictly following the control pathway by endemic countries can lead to improvement in global FMD situation. (The contributor is a 3rd year student of the College of Veterinary Sciences and Animal Husbandry, Selesih, Mizoram)
