China has reported a mysterious spike in the number of dead pigs, including baby pigs, turning up near Shanghai. This is prompting our revisit of the pig virus contamination issue with rotavirus vaccines that raised some eyebrows in 2010.
Where Are the Pigs From and How Did They Die?
The fact is that more than 13,000 pigs have turned up dead in and along the Huangpu River and nearby area during the past few weeks. Authorities have yet to isolate any one cause of the deaths, how or where the pigs originated
Even though the Agriculture Ministry has stated there is "no major swine epidemic," one suspected cause of death is pointing to porcine circovirus (PCV), as samples of the deceased pigs have tested positive for the common pig infection that has not yet been shown to be harmful to humans. Authorities have also assured Shanghai residents that the drinking water from the Huangpu River−−a major supplier for the city of Shanghai−−is safe. 1 2
Jiaxing, where thousands of hog farms are located and where there have been previous reports of inexplicable pig deaths, is the suspected main source. Some of the pigs had ear tags from from Jiaxing. 3
How Are Pig Deaths Related to Rotavirus Vaccines?
Porcine circovirus types 1 and 2 (PCV1 and PCV2) have been in the news before as a potential threat to public health. Although PCV1 infection is thought to be relatively harmless in pigs, PCV2 is associated with a lethal wasting disease in baby pigs.. 4
In May 2010, the Food and Drug Administration (FDA) temporarily suspended use of GlaxoSmithKline's (GSK) rotavirus vaccine, Rotarix, because DNA from PCV1 was found in the vaccine. Merck's RotaTeq was found to contain PCV1 plus PCV2 DNA fragments, but its use was not suspended.
Shortly thereafter, the FDA said use of Rotarix could resume because the vaccine had "strong safety records" and there is "no evidence that either PCV1 or PCV2 poses a safety risk in humans." 5 6
NVIC Calls For Elimination of Pig Virus DNA From Rotavirus Vaccines
In 2010, NVIC called on GSK to eliminate PCV1 DNA from Rotarix and called on Merck to voluntarily recall RotaTeq until the vaccine was free from PCV2 DNA fragments because PCV2 is “an aggressive virus that causes immune suppression, wasting disease and death in baby pigs.” 7 No such action occurred.
The FDA asked both GSK and Merck to update labels for Rotarix and RotaTeq to include information about the presence of DNA from porcine circoviruses, which the drug companies have since done. 8 9 But the pig virus DNA is still present in the vaccines and strong evidence that it is safe for infants to swallow pig virus DNA in live rotavirus vaccines is still missing.
EMA Proposes Guidelines On Use of Pig Products In Vaccines
In response to the questions surrounding porcine circoviruses, the European Medicines Agency (EMA) has been working to tighten quality controls. In February, the agency published draft guidelines for use of trypsin, a protein-processing enzyme derived from the pig pancreas that is thought to be the origin of PCV contamination. The guidelines suggest ways to minimize the risk of contamination, such as selecting healthy pigs, testing of starting material for adventitious agents, appropriate cleaning methods during the manufacturing process and quality controls. The EMA also noted that there are alternative reagents available other than porcine trypsin that should be explored.
The EMA concluded that vaccine manufacturers “should have sufficient information on the trypsin to allow a comprehensive risk assessment and provide a sufficient data package to the competent authority for assessment.” 10
China’s Turn For Action
Public health and food safety issues in China have a history of being disastrous (think SARS). So it is only natural to be concerned when pig carcasses are turning up by the thousands. The hope is that a full investigation will reveal exactly how and why the pigs died.
References:
1 Associated Press. Dead Pig Count in China’s Waters Near Shanghai Spikes. March16, 2013.
2 More Than 13,000 Dead Pigs Turn Up in Shanghai Waters. Food Safety News. March 8, 2013.
3 Hongyi W. Epidemic ruled out as cause of dead pigs. China Daily March 13, 2013.
4 Background on PCV. Food and Drug Administration Vaccine, Blood & Biologics. (Updated May 14, 2010).
5 Update on Recommendations for the Use of Rotavirus Vaccines. Food and Drug Administration. May 14, 2010.
6 McClenahan SD, Krause PR, Uhlenhaut C. Molecular and infectivity studies of porcine circovirus in vaccines. Vaccine 2011; 29:4745-53.
7 NVIC.org. Vaccine Safety Critics Call For RotaTeq Vaccine Recall & Clean-Up. June 1, 2010.
8 Rotarix. Food and Drug Administration Vaccines, Blood & Biologics. Online. (Updated June 4, 2010).
9 RotaTeq. Food and Drug Administration Vaccines, Blood & Biologics. Online. (Updated Dec. 12, 2012).
10 European Medicines Agency. Guideline on the use of porcine trypsin used in the manufacture of human biological medicinal products. Feb. 21, 2013.
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