"There have been no known human cases associated with these prairie dog shipments," David Dennis, an epidemiologist with the Centers for Disease Control and Prevention, said at a news briefing. However, "there is concern about persons who have handled sick or dead animals" over the past three weeks, he said.
People who have been around prairie dogs and have symptoms of the disease -- which can include fever, muscle achiness, chills and headache -- should seek out medical attention immediately, Dennis said.
Dennis noted people generally must be bitten or scratched or come into contact with secretions from infected animals to contract tularemia. Even people who are not sick but who have had contact with prairie dogs should contact a physician because antibiotics can prevent symptoms from developing as well as treat them effectively if they are present.
Other symptoms may appear depending on how the disease was acquired. Most cases enter through the skin and often an open sore and swollen lymph nodes will develop around the site of entry. The bacteria also can be ingested and this generally will cause sores in the mouth and swollen lymph nodes in the neck, Dennis said.
The disease, which cannot be spread from person to person, usually is not fatal. However, the young, the elderly and the immunocompromised may be more vulnerable to death from the disease.
The outbreak began in mid-July and since then authorities have been working to determine its source and where the infected animals were sent. The prairie dogs were caught in Texas and South Dakota and shipped from a distribution center in Denton County, Texas, to pet stores around the world.
CDC officials have determined during the past two months "hundreds of prairie dogs that may potentially be infected with the bacteria were shipped to a number of outlets in various states including Ohio, West Virginia, Florida, Washington, Mississippi, Nevada, Texas, Illinois, Virginia," the agency said in a written statement. "In addition, prairie dogs were also shipped to Japan, (the Czech Republic), (the Netherlands), Belgium, Spain, Italy and Thailand."
So far, sick or dead animals have been found in Texas, West Virginia and the Czech Republic, Dennis said.
Due to the potential for global spread of the outbreak, the World Health Organization and the European Union Disease Surveillance Network have become involved in the investigation.
Tularemia also is a potential bioweapon and is among the CDC's top six agents of concern, although this outbreak does not appear to be a bioterrorist attack, experts told United Press International.
"This is not a way terrorists are going to try to spread tularemia," said R. Gregory Evans, director of the center for the study of bioterrorism and emerging infections at Saint Louis University. Terrorists are more likely to aerosolize tularemia so it can infect the lungs, which increases the lethality of the agent significantly, he said.
"That can almost never happen naturally," Evans said.
Stephen D. Prior, a bioweapons expert at the Potomac Institute for Policy Studies, a think tank in Arlington, Va., agreed, saying, "I don't' think we'll see the (aerosolized form of tularemia) from prairie dogs."
The CDC noted about 200 human cases of tularemia occur each year in the United States and the disease usually is acquired from handling infected rabbits or being bitten by infected ticks.
(Reported by Steve Mitchell, UPI Medical Correspondent, in Washington)