Foot and Mouth Disease (FMD)

Description

The virus affects all ruminants and pigs. The morbidity of the animals is up to 100%, while the mortality rate is low (5%). However, the infected individual sheds the virus into the external environment throughout the course of the disease. Foot-and-mouth disease is spread directly between animals by inhalation or contact. The virus is present in high concentrations in vesicular fluid and saliva, but is shed in urine, faeces and milk. Indirect transmission is the other major route of spread - contaminated footwear and clothing of workers, transport vehicles, agricultural machinery and animal products. In the affected area, the virus can spread very rapidly, depending on the infectious dose and the size of the susceptible population.

Laboratory diagnostics

1. Samples suitable for laboratory examination

Sample collection to test for the presence of virus in case of suspected SLAK:

• epithelium from fresh vesicles
• vesicular fluid
• oropharyngeal scrapings (Probang test)
• buccal mucosal swabs
• saliva
• blood
• serum
• milk
• semen

Sample collection for antibody testing:

• serum
• plasma

2. Laboratory diagnostics

2.1 Virus detection

The virus is detected from the sample by RT-PCR. If positive, the virus is typed by antigen ELISA. For virus isolation and subsequent amplification, it is important to preserve the live virus and therefore the sample is collected in glycerol-phosphate buffer.

In cattle, a persistently infected carrier may occur after recovery and 28 days, in which case a virus sample can only be obtained by oropharyngeal swabbing (Probang test). The oropharyngeal scraping sample (Probang test) is stored in Probang buffer.

The virus appears in oropharyngeal swabs up to 2 days before the onset of clinical signs.

SLAK virus appears in the blood 1-2 days before the onset of clinical signs and disappears 5 days after the onset of clinical signs.

2.2 Detection of antibodies

Antibodies to SLAK are produced in serum from day 2 after the onset of clinical signs. Antibodies are tested by NSP ELISA, which can detect post-infectious antibodies. If positive, the antibodies are typed by serotype ELISA.