Foot and Mouth Disease
Foot and Mouth Disease
Foot-and-mouth disease (FMD) is a highly contagious viral disease of cattle, buffalo, pigs, goats, sheep and other cloven-hoofed animals. The occurrence of FMD is associated with serious consequences for the affected countries. Wild cloven-hoofed animals, such as deer, antelope, wild boar, giraffe, and camel can also become infected. Horses are not susceptible to FMD; human infection (in occupationally exposed individuals) may occasionally occur but does not usually result in disease.
The foot-and-mouth disease virus (FMDV) is almost worldwide in distribution, with only New Zealand having no recorded FMD outbreaks to date. The disease is endemic in Africa, Asia, the Middle East and parts of South America. Other regions may experience sporadic outbreaks: for example, FMD in Europe has occurred twice in the 21st century in the UK (2001 to 2002 and 2007).
General symptoms in all affected species are blistering (aphthae) of the mouth, udder, and hooves; fever (40-42°C), pain, apathy, loss of appetite, lameness, and decrease in milk yield. Morbidity can reach 100%. The death rate is usually low (up to 5%) in adult animals, but may be 20% or more in young calves, lambs, and piglets.
Situation in Austria
The last outbreak of foot-and-mouth disease in Austria was in 1981.
Foot-and-mouth disease is a notifiable animal disease. In the event of a suspected epidemic, the official veterinarian must initiate an immediate closure of the farm and a suspect investigation. Cases of disease in individual animals that show symptoms reminiscent of FMD (mostly skin changes), on the other hand, are quickly clarified in the course of exclusion examinations without a farm closure. Nevertheless, the official veterinarian must be consulted in this case as well. In 2022, FMD was investigated in six cases in the course of exclusion examinations, and a further 11 samples from zoo animals were tested for FMDV antibodies.
FMDV is a non-enveloped RNA virus belonging to the genus Aphtovirus of the family Picornaviridae with currently a total of 7 serotypes, with numerous subtypes within each serotype. Historically, the 7 serotypes are designated A for "Allemagne", O for department "Oise", C, Asia 1 for the first Asian detection, and SAT 1-3 for "South African Territories". Serotype C is now considered extinct. Some viral strains are specifically adapted to pigs; other species may play a role in the spread of infection, but their importance as reservoirs is uncertain. The pathogen typically shows high affinity for epithelial tissue:
- Epitheliotropism: skin and cutaneous mucosa.
- myotropism: skeletal and cardiac muscles
- Neurotropism (very rare): Nervous tissue
General symptoms in all affected species are aphthous formation (blisters, vesicles) on the udder (teat, resistance to milking), claws (interclaw cleft, coronal border, in pigs aphthous formation up to the tarsal joint, reluctance to move, clattering, slow standing up) and mouth (inside of lips, tongue, gums, animals salivate and show reduced desire to eat); fever (40-42 °C), pain, apathy.
Other symptoms in cattle: decrease in milk yield, high mortality rate in calves.
Other symptoms in pigs: changes in claws/extremities often very severe, shoeing possible, deaths in piglets without clinical signs common.
Other symptoms in sheep: mainly fever. Lameness and lesions in the mouth area are often mild. Peracute deaths in young animals.
FMD is clinically indistinguishable from other vesicular diseases (e.g., porcine vesicular viral disease, vesicular stomatitis); therefore, appropriate laboratory diagnosis or exclusion of the disease by laboratory testing is essential. Suitable specimen materials are:
- Epithelium of unruptured or freshly ruptured vesicles (aphthae) in dry, sterile screw-top tubes, or in suitable transport medium (see below).
- Vesicle contents in dry, sterile screw tubes
- Esophageal/pharyngeal fluid (so-called probang specimens) in dry, sterile screw-top tubes, or in suitable transport medium (see below)
- Swabs (e.g. swabs from already older ruptured vesicles, or nasal/vesicle swabs in case of suspected FMD without clear changes)
- Whole blood (note: whole blood alone is not sufficient for diagnosis due to the short viremia; tissue, vesicle contents, swabs, or probang samples must also be examined!)
- Milk (for dairy cattle)
The shipment of the sample materials should be carried out as quickly as possible after notification (optimally with refrigerants) in compliance with the relevant transport regulations (UN3373) and by a suitable logistics company to the investigating laboratory. The detection of FMDV from above materials is possible with the following methods:
- Molecular biological identification by RT-PCR (vesicle epithelium, vesicle fluid, swabs, milk, probang samples, serum).
- Antigen ELISA (vesicle epithelium, vesicle fluid)
- Virus culture (vesicle epithelium, vesicle fluid, probang samples, serum): for virus isolation from vesicle material or probang fluid, it must be shipped in an appropriate buffered transport solution, which can be obtained from the laboratory
- Serological test methods for antibody determination: ELISA, serum neutralization test (serum)
- Serotyping, or further pathogen characterization:
- Antigen ELISA
- Serotype-specific RT-PCR
- Serotype-specific ELISA
- Serum neutralization test
Last updated: 26.05.2023