Foot and Mouth Disease

Anna O'Brien, DVM
Published: August 2, 2013
Foot and Mouth Disease

Foot and Mouth disease (FMD) is a highly infectious disease of livestock that is endemic in many countries and results in production losses of very high financial magnitude. The U.S. has not had an outbreak of this disease since the 1920s, due mostly to the USDA’s strict animal import laws and our geographical luck in having to only monitor two international borders instead of the multitudes seen in Europe, Africa, and Asia. However, this disease is still very active in other countries.

FMD is caused by a virus and is rarely fatal. Its devastation is a result of the lesions it causes: blisters on the lips, gums, feet, and mammary glands. These lesions are extremely painful and an affected animal will be reluctant to move and eat, thus resulting in weight loss. FMD has a mortality rate of around 1 to 5 percent, but its morbidity rate, the chances of members of the population becoming infected, is close to 100 percent. This means once it is in a herd, it spreads like wildfire.

Cattle, hogs, sheep, and goats can all be affected, and the virus can jump from one species to the next. This disease can be confused with hand, foot, and mouth disease (HFMD), a viral disease that affects children. Humans cannot catch FMD and animals cannot catch HFMD; they are two different viruses. However, humans, as well as horses, cats, dogs, and birds, can act as mechanical vectors for FMD, meaning we can spread the virus from farm to farm. After an infected animal recovers, it can then be a carrier of the virus as well.

Some of the more recent outbreaks in countries such as the U.K., Vietnam, and China began when animals, typically hogs, were accidentally fed imported food that contained meat from infected animals. FMD virus is also adept at surviving in soil, dry fecal material, and slurry for lengthy periods of time.

As you can see, FMD is tricky, extremely tricky. Its clinical signs are also very similar to other reportable, highly contagious diseases such as vesicular stomatitis, swine vesicular disease, vesicular exanthema, and other blister-causing diseases, all of which make inspectors understandably very nervous.

The usual mode of action during an outbreak is the slaughter of all infected and exposed animals. This is somewhat unsettling due to the fact that the disease itself is rarely fatal. However, due to its extreme infectiousness and cause for mass loss of production, mass slaughter is the most efficient and effective way to halt its spread.

I lived in the U.K. at the start of their 2001 outbreak of FMD. I recall the huge pyres of burning euthanized animals and how many of the lovely hiking trails across the country’s farm pastures were closed to prevent spread by human shoes. I also remember being nervous for the farm where I was working. It was a horse farm, but they had a handful of sheep. They installed footbaths at all doors of the barns and we had to scrub with bleach water upon entering and exiting. Luckily, their small operation remained safe, although others not far down the road weren’t so lucky. Entire farms had to be depopulated; farmers lost their entire livelihoods. It was devastating to England’s agricultural industry and heartbreaking to watch.

About a year ago, the USDA announced a conditional license had been granted for a FMD vaccine that was allowed to be manufactured on the U.S. mainland. Previously, all FMD vaccines contained live FMD virus. Since the U.S. is free of the disease, the U.S. was not a fan of the potential danger of a live virus being in a manufacturing plant on the mainland (FMD was studied at Plum Island, a foreign animal disease lab off of New York state). Additionally, because older vaccines contained live virus, it was sometimes difficult to diagnostically differentiate between infected animals, carrier animals, and those that had been vaccinated — vital distinguishers if a country is attempting to de-populate based on infection.

Although there is currently no need for producers in the U.S. to start vaccinating their herds against FMD, this new vaccine is considered a breakthrough. It gives the U.S. the advantage of no longer being dependent on foreign vaccine manufacturers in the case of an outbreak here and has potential to save lives overseas, as well; lives that would be lost through confusion of exposure versus vaccination.

Dr. Anna O’Brien

Image: smereka / Shutterstock

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