|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
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
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
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.