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Much to learn about foot-and-mouth disease: Part 1

Vet Advice with Dr. Ron Clarke

This article is the first of a series of three dealing with foot-and-mouth disease (FMD) and emergency planning.

Through May and June of 2020, 88 veterinarians and registered animal health technologists from across Canada and the U.S. participated in a series of webinars dealing with the control of FMD. A panel of experts from the European Commission for the Control of Foot and Mouth Disease prepared and delivered the course, assisted by the Canadian Food Inspection Agency (CFIA) and the Animal Health Emergency Management Project.

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An interesting mix of staff from private veterinary practices, government, diagnostic labs and research organizations sought new and updated information on:

  • How the disease develops when the virus infects an animal.
  • Clinical signs and the progression of lesions in cattle, sheep and pigs.
  • Appropriate submission of diagnostic samples.
  • Epidemiological investigative techniques when FMD is suspected or after it is confirmed.
  • Correct biosecurity practices when entering or leaving premises where FMD is suspected.
  • Key aspects of control measures used in a FMD outbreak in a previously free country.

FMD remains endemic in many parts of the world. It is a threat to the Canadian livestock industry through visitors, trade in animal products, shipments of illegal meat products and bioterrorism. The probability of the virus entering FMD-free zones is a function of risk and frequency. For instance, the import of illegal meat products by air, ship and mail from Asian countries into North America is quite shocking. The amount is measured in tonnes every year; the frequency daily.

FMD has been recognized as a significant epidemic disease, threatening cattle worldwide since the 16th century. In the late 19th century, scientists showed FMD to be a submicroscopic, filterable, transmissible agent, smaller than any known bacteria. In 1514, Hieronymi Fracastorii provided the earliest description of a disease resembling FMD affecting cattle in northern Italy. In 1780 from South Africa, Le Vaillant (1795) described a disease in cattle, which “attacked the feet of oxen causing them to swell prodigiously and after producing suppuration, sometimes the hooves dropped off.”

The agent causing FMD represents the first virus of vertebrates to be discovered. Its discovery followed identification of tobacco mosaic virus in plants. By 1920, Waldmann and Pape showed that guinea pigs were a convenient animal model for the study of FMD virus, followed by development of in vitro cell culture systems for the virus. The chemical and physical properties of FMD virus were elucidated during the remainder of the 20th century, culminating in 1989 with a complete description of the three-dimensional structure of FMD virus.

Seven main serotypes of FMD exist, with numerous subtypes. The World Reference Laboratory for FMD is located at Pirbright, Surrey, U.K. Scientists at Pirbright undertake surveillance of FMD epidemics by serotyping and genotyping isolates of the virus from around the world.

FMD is still described as a highly contagious, acute viral disease affecting cloven-footed animals, including pigs, cattle, sheep and goats. The disease is characterized by the formation of vesicles and erosions inside the mouth and on the nose, teats and feet. Mortality is low in adult animals, but death commonly occurs in young animals.

Canada’s $21 billion livestock sector, much of it channeled toward export, is tempered by its health status. Freedom from serious diseases opens many doors. Disease control programs and Canada’s ability to respond remains unequalled in many parts of the world and forges the trust that our health status is genuine. FMD within Canada’s borders would be catastrophic.

FMD remains one of nature’s most contagious agents. It can be spread through direct contact between animals, contaminated clothing, animal waste, wind and in meat and animal products (milk, semen, hides, hair). Seven endemic pools of FMD virus exist around the world. There has been long-distance movement of FMD virus from South Asia (Pool 2). As well, efficacy of existing vaccines against South Asia serotypes, as tools for FMD control, remain questionable. When a country or zone experiences an outbreak, the free status of an entire country is suspended. A lengthy process is involved to regain disease-free status.

The livestock industries in developed countries, under the tutelage of organizations like the EU Foot-and-Mouth Disease Training Team, constantly review individual response capabilities. Refinements and change through the years include:

1. Ability to age lesions, which provides a window on when the virus enters a premise, how it entered and when it leaves.
2. Appreciation of the value of thorough outbreak investigations that provide a basis for measuring transmission/spread; an opportunity to evaluate biosecurity measures and consider vaccination; and a chance to evaluate awareness.
3. Acceptance that the OIE (World Organization for Animal Health) remains the standard-setting body of the World Trade Organization. OIE guidelines help member countries protect themselves against the introduction of diseases.
4. Recognition that passengers entering Canada from FMD-endemic countries exceeded 4.5 million annually (2018). The most likely route for FMD virus entering Canada remains contaminated meat products.
5. Increased emphasis on early detection of FMD.
6. Training more people in effective investigative and response skills such as field diagnostics and biosecurity practices.

Countries recognize FMD eradication presently rests with four basic principles. They include eradicating the disease agent sources (stamping out); preventing contact between susceptible animals and the disease agent (movement control); vaccinating to increase resistance of susceptible animals; and containing the disease agent to a geographic area (zoning).

About the author

Columnist

Dr. Ron Clarke

Dr. Ron Clarke prepares this column on behalf of the Western Canadian Association of Bovine Practitioners. Suggestions for future articles can be sent to Canadian Cattlemen ([email protected]) or WCABP ([email protected]).

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