"Cattle car syndrome" offers SARS insights
Date: 21-May-03
Country: USA
Author: Maggie Fox, Health and Science Correspondent
It is caused by a coronavirus, the same class of viruses as the SARS virus, and the symptoms resemble those of SARS.
The conditions that can bring about shipping fever are similar to those affecting the travelers who spread SARS around the world, says Linda Saif, a professor of food animal health at Ohio State University.
Saif is one of a handful of experts on coronaviruses whose once-obscure field is now the center of attention in laboratories around the world, including at the World Health Organization, the U.S. Centers for Disease Control and Prevention, universities and at private companies seeking to market treatments, vaccines and diagnostic tests for SARS.
Two human coronaviruses cause about 30 percent of common colds, but the viruses cause more significant diseases in pigs, chickens and other livestock.
"There is a stress factor when animals are shipped long distances from farm to large feedlot," Saif told a weekend meeting of experts at the New York Academy of Sciences. "We are seeing SARS cases in patients that have traveled recently."
As any traveler can testify, these stresses include being away from home, being close to other strangers and moving across time zones, as well as rushing to catch flights.
Severe acute respiratory syndrome has killed 642 people and infected 7,860 across the world.
No one understands why SARS makes some people sicker than others and why some people seem to be more prone to spread it to others. It could come down to stress, or to infection with something along with SARS, such as flu or hepatitis.
Air travel throws large numbers of people together in small spaces, on aircraft and in airports. "When animals arrive at the feedlot they are commingled together," Saif said. "When animals arrive from other locations and commingle, you see disease outbreaks."
Saif said co-infection with other bugs is also known to worsen coronavirus infection in farm animals.
UNIQUE VIRUS MAKES SOURCE HARD TO FIND
Experts who examined the genetic map of the SARS virus say while it is related to the three families of coronaviruses that cause respiratory and gastrointestinal disease in animals, it is different enough to make up its own, fourth family.
It may have jumped from an animal to people, much as influenza does. "It is possible that maybe this was a human virus that no one recognized because it didn't cause disease and then it mutated," Saif said.
Attention has centered on farm animals because they have been widely studied, but experts at the conference said that did not necessarily mean SARS came from livestock.
"There's a lot of wildlife species out there that probably a lot of people haven't looked in," Thomas Ksiaszek, of the CDC's Special Pathogens Branch, told the New York meeting. "If I had to throw my two cents in, that would be my bet ..."
Some attention has centered on the "wet" markets of China's Guangdong Province, where SARS is believed to have originated in November 2002. Animals such as bears, monkeys and the endangered pangolin are sold in these markets for food.
Other studies suggest it may be difficult to fully control SARS in China and other hard-hit areas because people who have recovered from SARS may not have immunity.