In 2002, a brand new virus was discovered – not in the jungles of Africa – but in an unlikely place, a biotech company in suburban Maryland. The Seneca Valley virus was originally isolated as a contaminant in cell culture medium – likely from the pig trypsin used for the cultivation of the cells. The virus causes a vesicular disease in animals – that is, it causes blisters, particularly on the snouts and hoofs of infected pigs.     

Image/Scott Bauer, U.S. Department of Agriculture
Image/Scott Bauer, U.S. Department of Agriculture

“[This year], we have seen a pretty good uptick in cases in both show pigs and on commercial farms in Minnesota, Iowa, and South Dakota,” Minnesota Pork Executive Director Dave Preisler recently said in a radio interview. “Unfortunately, this [disease] looks exactly like foot and mouth disease,” Preisler went on to say.  

Foot and mouth disease (FMD) is a severe and highly infectious viral disease affecting cloven-hoofed animals. Despite the disease being only rarely fatal, a diagnosis of FMD often results in the slaughter of millions of animals, taking a heavy economic toll on the farmer. An even more substantial economic impact is felt by affected countries due to the agriculture trade bans that are imposed after a diagnosis of FMD. Countries designated FMD-free (without vaccination) by the World Organisation for Animal Health – the WHO equivalent for animal diseases – have the greatest access to export markets, so it is in the country’s best interest to maintain their current status.         

According to a recent news report in the Journal of the American Veterinary Medical Association, the Seneca Valley virus has been found in at least 12 U.S. herds in this year.  Dr. Paul Sundberg, executive director of the pork industry’s Swine Health Information Center, stated in the report that the mortality rates among the neonatal pigs in some infected herds were double the normal rates. The report also stressed that veterinarians need to treat any vesicular disease as a possible FMD infection and report the infection to state or federal animal health authorities.  

This outbreak, and the widespread occurrence of the disease in general, is concerning to U.S. agricultural officials because they do not want veterinarians and swine producers to become complacent and start thinking all cases of vesicular lesions in pigs are due to Seneca Valley virus and forget about FMD.

Sundberg also points out, “the virus has spread across the U.S., appearing in states ranging from Alabama to Hawaii. How the virus spreads and where it originated remain unknown.” In addition to occurring throughout North American, the virus was recently confirmed to be the cause of vesicular disease of pigs in several Brazilian states.

Chris A. Whitehouse is a microbiologist and science writer who lives in Maryland.  He writes extensively on emerging infectious diseases of humans and animals.  

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