Foot-and-mouth disease (FMD) is a serious and highly contagious viral disease of livestock that has a significant economic impact. It is one of the most serious livestock diseases. It affects cloven-hoofed animals (those with split hooves), including cattle, buffaloes, camels, sheep, goats, deer and pigs. The effect on trade in livestock and livestock products. The greatest impact of the disease occurs through its effect on trade in livestock and livestock products.
The disease is caused by infection with a Aphthovirus, a member of the Picornaviridae family. There are 7 serotypes of the virus, called: A, O, C, Asia 1 and SAT (Southern African Territories) 1, 2 and 3. These are subdivided into more than 60 strains.
Foot-and-mouth disease is a viral disease that spreads rapidly between animals. The virus can be shed by animals up to four days before the onset of clinical signs. It excretes through breath, saliva, mucus, milk and feces. While infection occurs through inhalation, ingestion and direct contact. The disease is most often spread by moving infected animals.
The foot-and-mouth disease virus can also spread on wool, hair, grass or straw; by the wind; or by mud or manure adhering to footwear, clothing, livestock equipment or vehicle tires.
The interval between exposure to infection and the appearance of symptoms varies between 24 hours and 10 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 below 6.0, i.e. after rigor mortis.
How does it infect animals?
Foot-and-mouth disease affects all ages, but it can be particularly deadly in young animals and cause serious production losses.
Clinical signs in cattle include a fever of approximately 40°C, followed by the development of vesicular lesions on the tongue, hard palate, dental pad, lips, gums, muzzle, coronal band, interdigital cleft and teats in lactating cows. Severely affected people may salivate profusely (drool), tap their feet and prefer to lie down. The blisters on the feet take longer to heal and are susceptible to bacterial infections leading to chronic lameness. Secondary bacterial mastitis is common due to infected teat blisters causing resistance to milking. Young calves may die without prior clinical signs of disease due to virus-induced damage to the developing myocardium.
In cattle, the clinical signs of foot-and-mouth disease are indistinguishable from those of vesicular stomatitis. Therefore, laboratory confirmation is essential for the diagnosis of FMD and should be carried out in specialized laboratories.
Laboratory diagnosis is usually made by real-time RT-PCR testing in two separate assays targeting two different regions of the RNA genome. These tests are very sensitive and can detect FMDV genomes.
The presence of viruses can also be identified using antigenic ELISAs, which can determine the serotype. This is the preferred method in FMD endemic countries for virus detection and serotyping.
In reference laboratories, sequencing of part of the genome is frequently carried out to determine the serotype and lineage of the strain. Simultaneous virus isolation can be performed in appropriate cell culture systems. Commercially available lateral flow devices for rapid pen-side viral antigen detection have proven useful.
There is no specific treatment for foot-and-mouth disease. In pandemic countries, antibiotic therapy can be used to control secondary bacterial infection of ulcers, but healing takes several weeks to months.
The property and its surroundings will be quarantined, inspected and disinfected if necessary. Movement restrictions on remaining animals and surrounding properties will be put in place until they are declared disease free. In some cases, restrictions on the re-entry of animals to affected properties may be in place for up to 12 months.
How to prevent foot-and-mouth disease?
Foot-and-mouth disease is one of the most difficult animal infections to control. Outbreaks are generally controlled by quarantines and movement restrictions, euthanasia of affected and in-contact animals, and cleaning and disinfection of affected premises, equipment and vehicles.
Infected carcasses should be disposed of safely. Milk from infected cows can be inactivated by heating it to 100°C (212°F) for more than 20 minutes. While slurry can be heated to 67°C (153°F) for three minutes.
Rodents and other vectors can be killed to prevent them from mechanically spreading the virus. In addition, good biosecurity measures should be practiced in uninfected farms to prevent virus entry.
At the same time, vaccinating animals can reduce the spread of foot-and-mouth disease. Vaccination must be specific to the different strains. Vaccination with one serotype does not protect the animal against the other serotypes. Currently, there is no universal vaccine against foot-and-mouth disease.
(The author is a 3rd year BTech Dairy Technology student at College of Dairy Science and Technology, Kolahalamedu, Idukki)