United States-Effect of swine flu on farming and meat trade.
UNITED STATES-SWINE FLU.
While Agriculture Secretary Tom Vilsack says there is "no evidence" of the new swine flu in U.S. pigs, the federal government doesn’t aggressively search for it on farms.
Mr. Vilsack’s statement is designed to bolster the Obama administration’s argument that U.S. consumers and trading partners haven’t any reason to shy away from eating U.S. pork. But the observation isn’t based on any extensive sampling program of the sort that is used by the federal government to alert it to other animal disease, such as mad-cow disease and bird flu.
Indeed, only in recent months has the Agriculture Department begun organizing a federal pilot program for screening pigs for flu. And that move came at the prodding of officials at the U.S. Centers for Disease Control and Prevention. CDC officials have been worried that pigs might serve as a "mixing vessel" for a flu virus capable of sweeping through the human population. The pilot program has yet to begin to collect samples.
In the U.S. , the testing of pigs for flu has been done at the instigation and expense of farmers, who are usually trying to figure out why a vaccine isn’t working. Private veterinarians ship flu samples to state-government-staffed diagnostic laboratories, the busiest of which include the University of Minnesota and Iowa State University .
USDA scientists are collecting reports on the genetic analysis work of the state-run laboratories to see whether anything suspicious ever turned up in pigs before swine flu erupted in humans in Mexico and the U.S. As part of this review, scientists at the state veterinary laboratories are scrambling to find old flu samples that weren’t fully genetically sequenced for one reason or another.
John Clifford, the USDA’s top veterinarian, said the department has collected from state laboratories their analysis of 500 virus samples taken from sick U.S. pigs since September. None of these U.S. pig samples was a match for the new H1N1 virus found in humans.
"The secretary was absolutely correct when he said there were no reported cases" in U.S. pigs, Dr. Clifford said.
Still, veterinary experts say it’s impossible to know whether U.S. pigs are free of the new virus, which was detected over the weekend in a Canadian hog herd. Farmers aren’t required to report flu outbreaks in their pigs to authorities, and the collection of the 500 samples wasn’t designed to detect a low level of a new virus in U.S. swine, of which there are about 65 million head.
To monitor mad-cow disease, for example, the USDA annually samples about 40,000 high-risk cattle. According to statistical analysis, such a sampling level should find the brain-wasting disease if it is striking just one in a million head of cattle. The government oversaw the screening of nearly 113,000 chicken flocks for bird flu during the year ended Sept. 30, 2008.
Until recently, monitoring flu outbreaks in pigs wasn’t a high priority for the USDA because the disease traditionally was viewed as mild. While bird flu viruses can be so pathogenic that they infect the blood and muscle of their hosts, flu viruses in pigs usually stay in the animals’ respiratory system, where the viruses aren’t much of a threat to consumers.
The concern about swine flu in pigs within the international veterinary community has been so low that an outbreak doesn’t have to be reported to the World Organization for Animal Health, the Paris body through which 172 member nations coordinate their attacks against animal diseases.
In the wake of the H1N1 outbreak in people, however, the Paris group is preparing to debate whether pig-borne flu is enough of a threat to people for it to be a reportable disease, which would require the establishment of a farm-level surveillance standard for its members to follow. The Paris body is slated to meet in late May.
