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ESSENTIAL DESTINATIONS

MONTH: March 2008

Heparin crisis rekindles concern about disease from pig transplants

 

DEERFIELD, Ill.; chang-zhau--Concern about the possibility of pig diseases crossing into humans through medical procedures using pig byproducts rose worldwide after the drug maker Baxter International on February 25, 2008 suspended sales of the blood-thinning product heparin.

Baxter International, of Deerfield, Illinois, reportedly distributes more than a million doses of heparin annually, amounting to about half of the U.S. supply.

The U.S. Food & Drug Administration linked four human deaths and as many as 400 complications of illnesses to bad reactions to heparin in the weeks preceding the recall.

"Investigators are trying to determine whether the raw material for the drug, made from pig intestines, became contaminated on the journey that begins in the slaughterhouses of China," reported David Barboza and Walt Bogdanich of the New York Times.

Baxter International buys crude heparin for processing into the pharmaceutical product from Scientific Protein Laboratories, a U.S. firm that obtains the material from a subsidiary, Changzhou SPL, located in Changzhou, China.

On February 16, 2008, Bogdanich and Jake Hooker of the New York Times revealed that Changzhou SPL was not inspected as a pharmaceutical maker by either Chinese regulators or the FDA. Instead, like the Chinese source of pet food contaminated by the coal byproduct melamine that may have caused thousands of animal deaths worldwide during the winter of 2006-2007, Changzhou SPL was known to the Chinese government as a maker of industrial chemicals.

"One of the wholesalers named by Scientific Protein Laboratories, Ruihua Biochemical in Hangzhou, said it provided a mix of crude heparin that it manufactured and some that it bought 'from small factories nearby in several villages,'" Barboza and Bogdanich revealed on February 28, 2008. "Some experts say as much as 70 percent of China's crude heparin-for domestic use and for export-comes from small factories in poor villages," Barboza and Bogdanich continued.

Citing "interviews with dozens of heparin producers and traders in several Chinese provinces," Barboza and Bogdanich explained that "The Chinese heparin market has become increasingly unsettled. After an outbreak of blue ear pig disease swept through 25 of China's 31 provinces and regions last year, prices soared."

The blue ear epidemic, Shandong University School of Medicine heparin expert Cui Huifei told the New York Times, "made biotech companies inevitably purchase from the family-style plants, for cheaper prices."

The risk of pig diseases crossing into humans via medical procedures has concerned public health officials for decades, but heparin had not been seen as a likely vector. First isolated from canine liver cells in 1916, heparin debuted as a pharmaceutical product in 1933, and was first marketed in 1937. Pharmaceutical heparin was initially extracted from the remains of slaughtered cattle, but most heparin today is derived from the small intestinal submucosa of pigs--the same source as SIS, a patching material first used in the U.S. in 1988.

In February 2000 the FDA approved SIS for treatment of almost any sort of soft-tissue wound--even eye injuries and some types of stomach ulcer.

Other pharmaceutical products made from pig tissues are also now widely used, stimulating research into genetically modifying pigs to produce ready-to-transplant replacements for human organs. The pork production conglomerates Hormel and Smithfield have reportedly invested millions of dollars in the effort, with partners including Baxter Healthcare and the Mayo Clinic.

But in August 2000 the Roslin Institute of Scotland and Geron Bio-Med of California dropped efforts to produce transplantable organs
for humans in pigs, citing concern about the risk of accidentally transmitting pig endogenous retroviruses into humans.

Called PERVs for short, pig endogenous retroviruses do not harm pigs, and may not harm people, but British virologist Robin A. Weiss demonstrated in 1997 that cross-species infection can occur.

Because PERV invades cells in much the same manner as HIV, integrating itself into the genetic program of the host, the Roslin Institute and Geron Bio-Med preferred to avoid the potential liability if a PERV strain ever attacks humans.