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How do you Diagnose Foot and Mouth Disease?
History & Significance
Symptoms & Pathogenesis
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1. Clinical signs

Foot and Mouth Disease (FMD) cannont be diagnosed on clinical signs alone. Laboratory tests are needed to confirm that an animal is or has been infected with the foot and mouth virus.

2. Collection of Samples
Consideration must be given to what the purpose of sample collection is so that an appropriate echoice of diagnostic test (see diagnostic tests) and sample type is made. For example, samples may be taken from animals or the environment for a variety of purposes, such as disease surveillance, health certification or monitoring the response to treatment or vaccination.

* Note that the information presented here is based on guidelines of the World Organization for Animal Health  Manual of Diagnostic Tests and Vaccines for Terrestrial Animals 2009 (OIE, the international governing body monitoring disease status and regulating trade with respect to foot and mouth disease) and the Canadian Food Inspection Agency (CFIA). For more detailed information please see those websites.

Collection of samples
What to collect and how?
Information to be sent with sample
Packaging and shipment of samples

3.  Laboratory Diagnostic Tests

Collection of Samples

Biosecurity concerns: Since Foot and Mouth Disease is a highly infectious substance, certain precautions need to be taken while collecting, shipping and transporting samples to the laboratory. The laboratory diagnosis and serotype identification of the virus should be done in a facility that meets the requirements for Containment Group 4 pathogens. In Canada, this is the National Microbiology Laboratory, and this is the only diagnostic laboratory to send samples to in Canada.

What to collect and how?

Acute Phase of  Disease:
When animals are currently showing clinical symptoms, the tissue of choice is epithelium or vesicular fluid. Ideally, at least 1 g of epithelial tissue should be collected from an unruptured or recently ruptured vesicle, usually from the tongue, buccal mucosa or feet. The vesicular fluid should be sampled where unruptured vesicles are present; if possible, vesicular fluid should be aspirated with a syringe and placed in a separate sterile tube. Epithelial samples should be placed in a transport medium composed of equal amounts of glycerol and 0.04 M phosphate buffer, pH 7.2–7.6, preferably with added antibiotics (penicillin [1000 International Units (IU)], neomycin sulphate [100 IU], polymyxin B sulphate [50 IU], mycostatin [100 IU]). Foot and mouth disease virus is extremely labile in low pH and buffering of the transport media is critical for successful sample collection. Samples should be kept refrigerated or on ice until received by the laboratory.

Convalescent of Recovery Phase of Disease:
Following recovery from the acute stage of infection, typically the infectious virus disappears with the exception of low levels that may persist in the oropharynx of some ruminants. Live virus or viral RNA may continue to be recovered from oropharyngeal fluids and cells collected with a probang cup (or in pigs by swabbing the throat). The purpose is to collect oro-pharyngeal fluid and especially superficial epithelial cells from these areas, including the proximal part of the oesophagus, the walls of the pharynx, the tonsillar crypts and the surfaces of the soft palate.

For collection of oropharynx samples 2 ml transport fluid (composed of 0.08 M phosphate buffer  containing 0.01% bovine serum albumin, 0.002% phenol red, antibiotics [1000 units/ml penicillin, 100 units/ml mycostatin, 100 units/ml neomycin, and 50 units/ml polymyxin], and adjusted to pH 7.2) should be added to a container of around 5 ml capacity capable of withstanding freezing above dry ice (solid carbon dioxide) or liquid nitrogen.

For the collection of throat swabs from pigs, the animal should be held on its back in a wooden cradle with the neck extended. Holding a swab in a suitable instrument, such as an artery forceps, the swab is pushed to the back of the mouth and into the pharynx.

Information to be sent with sample

Individual samples should be clearly identified using appropriate methods. Marking instruments should be able to withstand being wet or frozen (use indelible marking pen). Information and case history should always accompany the samples to the laboratory, and should be placed in a plastic envelope on the outside of the shipping container. As outlined in the following section on transport of samples, this information must also be inside the shipping container.

In addition to your contact information here is other relevant information that should be inlcuded.
  • Diseases suspected and tests requested.
  • The species, breed, sex, age and identity of the animals sampled.
  • Date samples were collected and submitted.
  • List of samples submitted with transport media used.
  • A complete history.

Packaging and Shipping Samples

The specimens should be forwarded to the laboratory by the fastest method available. If epithelial and vesicle samples can reach the laboratory within a 48 hours, then they should be sent refrigerated. If dry ice is used, the additional packaging requirements must be met. Infectious substances are not permitted to be shipped as checked luggage or as carry on luggage and must be shipped as cargo.

If oropharyngeal samples are to remain in transit more than a few hours, then they should be or frozen immediately after collection (preferably by placing either above dry ice or liquid nitrogen). Before freezing, the containers should be carefully sealed using airtight screw caps or silicone. This is particularly important when using dry ice, as introduction of CO2 into the oropharyngeal sample will lower its pH, inactivating any virus that may be in the samples. Glass containers should not be used because there is a risk that they will explode on defrosting in the event of liquid nitrogen leaking into them. Samples should reach the laboratory in a frozen state or, if this is not feasible, maintained under reliable cold conditions during transit.

Special precautions are required when sending perishable suspect foot and mouth material both within and between countries. The International Air Transport Association, Dangerous Goods Regulations has explicit requirements for packaging and shipment of diagnostic specimens by all commercial means of transport. Procedures for collection and shipment of field samples for the diagnosis of vesicular diseases and its differential diagnosis can be found at the Pan-American foot and mouth disease OIE Reference Laboratory.

FMD Quick Quiz

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Created September 2010
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