“It has created the most concern over a disease that doesn’t exist in our country that I have ever seen,” said Simon Kenyon, associate professor at Purdue University’s college of veterinary medicine. He was speaking of Britain’s foot-and-mouth disease outbreak at the Summit on FMD held earlier this week in Chicago. The event was sponsored by Watt Publishing and the Vance Food Systems Group.
While it’s true the United States hasn’t seen a case of FMD since 1929, the issue is very much alive in U.S. animal agriculture sectors, as well as the public in general.
“We don’t have it, but FMD is endemic nearly everywhere else in the world,” said Lawrence Firkins, director to the University of Illinois veterinary research stations. “It is one of the more feared, contagious and economically devastating livestock diseases.”
Currently, North America, Central America, Australia, New Zealand and Chile are FMD-free. The disease is widespread in Africa, Asia and South America. So far this year FMD has surfaced in the United Kingdom (which spread to some parts of Europe), the Middle East and Brazil.
FMD is a small, single-stranded RNA virus – which allows it to mutate. There are 7 types, and more than 60 subtypes of the virus. The disease has nearly a 100 percent morbidity rate, said Firkins, and a 50 percent to 100 percent mortality rate in young animals. The virus can harbor in the lymph nodes and bone marrow of an animal. Recovered animals – except for swine – can carry the disease.
The virus prefers low temperatures and high humidity, and is vulnerable at pH levels below 6 and above 9, which Firkins said can be used as part of a biosecurity program to contain or prevent virus exposure in herds. Under ideal conditions, the virus can survive for a year on premises, 10 to 12 weeks in feed and 28 to 36 hours on people. It does survive freezing and can be transmitted through fresh and frozen semen.
While the virus does travel through the air, Firkins said animal-to-animal transmission is the No. 1 vehicle.
The key to protecting the U.S. livestock and dairy herds is educating producers and veterinarians to recognize disease symptoms. “We had a 20-minute lecture on FMD in veterinary school, and I have never seen the disease,” said Firkins. What’s more, FMD symptoms can be confused with other more commonly seen diseases, which means they could be easily overlooked. In other cases, particularly in sheep, symptoms are subtle and can go unnoticed. Firkins suggested the following Web sites for more information on the virus: http://www.cvm.uiuc.edu/fmd/ and http://www.aphis.usda.gov/oa/pubs/fsfmd301.html.
FMD vaccines are available, but their use is controversial. “Vaccinating animals can help stop the spread in the face of an outbreak,” noted Firkins. “Vaccination zones can be developed to strategically create barriers between disease-free areas and infected areas.”
This is known as ring vaccination and the Netherlands used it to control an FMD break last year.
“You have to stay ahead of this disease, which is why immediate kill of all suspected animals is necessary,” said Simon Barteling, a veterinary consultant who has worked on FMD outbreaks in the Netherlands and South Africa. “But vaccines also can be an effective tool.” He pointed out that four days after the last animals was vaccinated in the Netherlands in September 2000, the outbreak calmed down and there were no new FMD cases.
Brazil and Argentina are currently vaccinating animals in an attempt to control FMD in those countries.
Barteling noted that today’s vaccines are much improved and that “to date, no vaccinated animals have caused disease.”
No single vaccine is effective against all seven types of the virus. Therefore, vaccines must match the active viral type and subtype to be effective.
The big issue surrounding vaccination is the fact that the country loses its FMD-free status and its ability to export during that time. Vaccinated animals must be slaughtered as part of the country’s clean-up program and attempt to regain FMD-free status. If a country vaccinates animals for FMD, it takes much longer for it to regain its FMD-free status compared to a natural FMD outbreak.
“I think that ring vaccination should carry the same FMD control status as slaughter alone,” concluded Barteling.