Foot and Mouth Disease

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cattle, buffalo, pigs, goats and sheep. The occurrence of FMD is associated with serious consequences for the countries affected. Wild cloven-hoofed animals such as deer, antelopes, wild boars, camels, giraffes and elephants can also be infected. Horses are not susceptible to FMD; human infection (in exposed persons) may occur occasionally, but does not usually lead to disease.

Occurrence

The foot-and-mouth disease virus (FMDV) occurs almost worldwide, with the exception of New Zealand, where no outbreaks have been recorded so far. The disease is endemic in Africa, Asia, the Middle East and parts of South America. Sporadic outbreaks can occur in other regions: for example, in Europe, FMD has already occurred twice in the 21^st century in Great Britain (2001 to 2002 and 2007).

Host animals

Cattle, buffalo and pigs are considered the main reservoirs of pathogens.

Mode of transmission

Transmission occurs through direct contact with infected animals, their products (e.g. milk, meat, semen) and excrements or contaminated inanimate objects. Airborne transmission is possible over considerable distances (up to 60 km by land).

Incubation period

2 to 14 days

Symptoms

General symptoms in all affected animal species are small ulcers (aphtae) on the udder, claws and mouth area; fever (40-42 °C), pain, apathy, lameness and decrease in milk yield. The morbidity can reach 100%. The death rate is usually low (up to 5%) in adult animals, but can be 20% or more in young calves, lambs and piglets.

Therapy

Vaccination is prohibited in the EU. Sick animals must be killed.

Prevention

Detection, isolation and eradication of infected FMD-positive animals; control of animal movements to prevent spreading of the disease.

The last outbreak of foot-and-mouth disease in Austria was in 1981.

Foot-and-mouth disease is a notifiable animal disease. If an epidemic is suspected, the official veterinarian must immediately close down the farm and start an investigation. However, cases of illness in individual animals which show symptoms reminiscent of FMD (usually skin lesions) are quickly clarified in the course of exclusion examinations without a holding being closed. Nevertheless, the official veterinarian must be consulted.

FMDV is an non-enveloped RNA virus belonging to the genus Aphtovirus of the family Picornaviridae. Currently 7 serotypes are known in total, with numerous subtypes within each serotype. Historically, the 7 serotypes are designated as A for "Allemagne", O for department "Oise", C, Asia 1 for the first Asian detection and SAT 1-3 for "South African Territories". Some virus strains are specifically adapted to pigs; other species may play a role in the spread of the infection, but their importance as a reservoir is uncertain. The pathogen typically shows high affinity to epithelial tissue:

• Epitheliotropism: skin and cutaneous mucous membranes
• Myotropism: skeletal and cardiac muscles
• Neurotropism (very rare): Nerve tissue

General symptoms in all affected animal species are aphtha formation (small ulcers) on the udder (teat, resistance to milking equipment), on the claws (interclaw gap, coronary band, in pigs aphthae up to the tarsal joint, unwillingness to move, tripping, slow standing up) and in the mouth area (inner side of lips, tongue, gums, animals salivate and reduced appetite); fever (40-42 °C), pain, apathy.

Other symptoms in cattle: decreased milk yield, high mortality rate in calves.

Other symptoms in pigs: changes in the claws/extremities often very severe, hoof loss possible, deaths in piglets without clinical symptoms frequent.

Other symptoms in sheep: mainly fever. Lameness and lesions in the mouth area are often mild. Peracute deaths in young animals.

FMD is clinically not to distinguish from other vesicular diseases (e.g. porcine vesicular viral disease, vesicular stomatitis), therefore appropriate laboratory diagnosis or exclusion of the disease by laboratory tests is essential.

Suitable sample materials are

• Epithelium of unruptured or freshly ruptured vesicles (aphtae) in dry, sterile screw vessels, or in a suitable transport medium (see below)
• Vesicle contents in dry, sterile screw vessels
• Oesophageal/pharyngeal fluid (so-called probang samples) in dry, sterile screw vessels, or in a suitable transport medium (see below)
• Whole blood (Attention: Whole blood alone is not sufficient for diagnosis due to the short viremia; tissue, vesicle contents, or probang samples must be examined as well!)

The sample materials should be shipped as soon as possible after notification (ideally in a cooled container) in compliance with the relevant transport regulations (UN3373) and with a suitable logistics company to the investigating laboratory.

The detection of FMDV from the above-mentioned materials is possible using the following methods:

• Molecular biological identification with RT-PCR (vesicular epithelium, vesicular fluid, probang samples, serum)
• Antigen ELISA (vesicular epithelium, vesicular fluid)
• Serological tests for antibody detection: ELISA, serum neutralisation test (serum)
• Virus cultivation (vesicular epithelium, vesicular fluid, probang samples, serum): samples for virus isolation from aphthae material or probang fluid must be shipped in an appropriate buffered transport solution which can be obtained from the laboratory
• Serotyping or further pathogen characterisation:
  • Antigen ELISA
  • Serotype-specific RT-PCR
  • Sequencing
  • Serotype-specific ELISA
  • Serum neutralisation test