Foot-and-mouth disease in cattle: Transmission, diagnosis, treatment and preventive measures

Meghna P

Representative Image / Photo: AP

Foot-and-mouth disease (FMD) is a severe, 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 divided hoofs), including cattle, buffalo, camels, sheep, goats, deer and pigs. The effect on trade in livestock and livestock products. The most significant impact of the disease occurs because of its effect on trade in livestock and livestock products.

The disease is caused by infection with an Aphthovirus, a member of the family Picornaviridae. There are 7 serotypes of the virus, termed: A, O, C, Asia 1, and SAT (Southern African Territories) 1, 2, and 3. These are further subdivided into more than 60 strains

How it is transmitted?

FMD is a viral disease that spreads rapidly between animals. The virus can be excreted by animals for up to four days before clinical signs appear. It excretes through breath, saliva, mucus, milk and faeces. While the infection happens through inhalation, ingestion and direct contact. The disease spreads most commonly through the movement of infected animals.

FMD virus can also be spread on wool, hair, grass or straw; by the wind; or by mud or manure sticking to footwear, clothing, livestock equipment or vehicle tyres.

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 less than 6.0, i.e., after rigor mortis.

How does it infect animals?

FMD impacts all ages but it can be particularly lethal in young animals and can cause serious production losses.

Clinical signs in cattle include fever of ~40°C, followed by vesicular lesion development on the tongue, hard palate, dental pad, lips, gums, muzzle, coronary band, interdigital cleft, and teats in lactating cows. Acutely affected individuals may salivate profusely (drooling), stamp their feet, and prefer to lie down. Vesicles on the feet take longer to heal and are susceptible to bacterial infection leading to chronic lameness. Secondary bacterial mastitis is common due to infected teat vesicles resulting in resistance to milking. Young calves may die without prior clinical signs of illness because of virus-induced damage to the developing myocardium.

How is FMD diagnosed?

In cattle, the clinical signs of FMD are indistinguishable from those of vesicular stomatitis . Therefore, laboratory confirmation is essential for diagnosis of FMD and should be performed in specialized laboratories.

Laboratory diagnosis is usually performed by real time RT-PCR assay in two separate assays targeting two different regions of the RNA genome. These assays are very sensitive and can detect FMDV genomes.

The presence of virus can also be identified using antigen ELISAs, and this can determine the serotype. This is the preferred method for countries with endemic FMD for virus detection and serotyping.

In reference laboratories, sequencing of part of the genome is frequently performed to determine the serotype and lineage of the strain. Concurrent virus isolation may be performed in appropriate cell culture systems. Commercially available lateral flow devices for rapid detection of virus antigen at the pen-side have proven useful.

How is FMD treated?

There is no specific treatment for FMD. In pandemic countries antibiotic therapy can be used to control secondary bacterial infection of ulcers but recovery takes several weeks to months.

The property and surroundings will be quarantined, inspected and disinfected as necessary. Movement restrictions on remaining animals and animals on surrounding properties will be put in place until they are declared disease free. In some cases, restrictions on re-introducing animals to affected properties may be in place for up to 12 months.

How can FMD be prevented?

FMD is one of the most difficult animal infections to control. The 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. Milk from infected cows can be inactivated by heating 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 may be killed to prevent them from mechanically disseminating the virus. Also, good biosecurity measures should be practiced on uninfected farms to prevent entry of the virus.

Meanwhile, vaccination of animals can reduce the spread of FMD. The vaccination should be specific for different strains. Vaccination with one serotype does not protect the animal against other serotypes. Currently, there is no universal FMD vaccine.

(The author is a 3rd year BTech Dairy Technology student at College of Dairy Science and Technology, Kolahalamedu, Idukki)

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