FMD: Diagnosis, Prevention and Control

Pashu Sandesh, 12 March 2019

Dr. Brajesh Kumar, Dr. Deepikesh Joshi, Dr. Vipin Chandra and Dr. Shashi Kumar

Foot-and-mouth disease (FMD) is a highly contagious viral disease of animals. It is one of the most serious livestock diseases. It affects cloven-hoofed animals which is caused by Picornavirus in Picornaviridae family.

Etiology

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-footed animals and is caused by the foot-and-mouth disease virus (FMDV), a small, non-enveloped virus that belongs to the genus of Aphthovirus, family Picornaviridae. FMDV occurs as seven major distinct serotypes: A, O, C, Southern African Territories (SAT) 1, SAT 2, SAT 3, and Asia 1. Each serotype has multiple subtypes with varying antigenicity and degrees of virulence, especially within the A and O types. 

Epidemiology 

It is a most contagious disease of animals with important economic losses. Low mortality rate in adult animals but high mortality rate in young animal due to myocarditis is seen. People can act as mechanical vectors of FMD by carrying virus on clothing or skin. FMD is not considered a public health problem, but there are reports of people working in FMD vaccine laboratories who have developed antibodies to the virus. The disease in people is usually short-lived and mild, with symptoms including vesicular lesions and influenza-like illness.

Susceptible Hosts 

Buffalo, cattle, sheep, goat, pig and ruminant wild animals

Mode of transmission

The virus is spread by aerosol and mechanical vectors and primarily colonise skin or mucous membranes. The virus is transmitted via direct or indirect contact with infected secretions and excretions (including semen and milk), mechanical vectors (people, horses, dogs, cats, birds, vehicles), and air currents over land or water. The virus can enter the body via inhalation, ingestion, or through skin wounds and mucous membranes. FMD has high agro-terrorism potential because of its infectivity, high transmissibility through wind and inanimate objects, and potential for large economic losses.

Clinical Findings:

Clinical signs in cattle include pyrexia of 104° F, followed by vesicular development on the tongue, hard palate, dental pad, lips, gums, muzzle, coronary band, interdigital cleft, and teats in lactating cows. Acutely affected inpiduals may salivate profusely, stamp their feet, and prefer to lie down. Ruptured oral vesicles can coalesce and form erosions but heal rapidly, roughly 11 days after vesicle formation. Feet vesicles take longer to heal and are susceptible to bacterial infection leading to chronic lameness. Secondary bacterial mastitis is common due to infected teat vesicles and resistance to milking. After vesicular disease develops, cattle quickly lose condition and milk yield, which can persist chronically. Lameness is usually the first clinical sign of FMD infection in sheep and goats. 

Diagnosis:

• Based on the history and clinical signs.
• Complement fixation test
• Virus isolation
• Laboratory diagnosis is usually performed via antigen capture–ELISA or serotyping ELISA. 
• Detecting nucleic acids via RT combined with real-time PCR is more sensitive and rapid than conventional methods and may be more useful when samples contain low concentrations of virus. 

Disease Treatment

There is no specific treatment of the disease other than supportive therapy, and antibiotics to prevent secondary infections.

Prevention

FMD is one of the most difficult animal infections to control.  FMD outbreaks are usually controlled by quarantines and movement restrictions, euthanasia of affected and in the contact animals, and cleansing and disinfection of affected premises, equipment and vehicles. Infected carcasses must be disposed off 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.

Vaccination

Vaccination can be used to reduce the spread of FMD and protect uninfected animals.  FMDV vaccines must closely match the serotype and strain of the infecting strain.Modern FMD vaccines perform very well both for regular prophylactic vaccination programs and for the control of outbreaks.

Thus, it is clear from the afore mentioned description that FMD is one of the most contagious disease of farm animals. Due to this reason, farmers/ livestock-owners should keep control and treatment of the disease in their farm practice to prevent the loss of their livestock and hence, the economic loss.     

Dr. Brajesh Kumar¹, Dr. Deepikesh Joshi², Dr. Vipin Chandra³ and Dr. Shashi Kumar⁴

¹Assistant Professor, Department of Veterinary Pathology, Apollo College of Veterinary Medicine, Jaipur (Rajasthan)

²Assistant Professor, Department of Livestock Production Management , Apollo College of Veterinary Medicine, Jaipur (Rajasthan)

³Research Scholar, Department of Livestock Production Management, Post Graduate Institute of Veterinary Education and Research (RAJUVAS), Jaipur (Rajasthan) 

⁴Assistant Professor, Department of Veterinary Anatomy, Apollo College of Veterinary Medicine, Jaipur (Rajasthan)