Influenza C Virus in Pigs

In 1982 a report[1] surfaced from Chinese scientists that they managed to isolate fifteen strains of Influenza C virus from abattoir pigs in China in 1981 and antibody against Influenza C virus was found in pig sera. Virus survey also showed seasonal activity of Influenza C virus in pigs.

Additionally, experimental infection of pigs with Influenza C virus demonstrated that Chinese domestic pigs could be infected by Influenza C virus and that the virus could be transmitted from pig to pig. These results indicate that, like Influenza A virus and Influenza B virus, Influenza C virus can cause natural infection in pigs.

[Image: Scott Bauer]

Further research[2] indicated that Influenza C virus in pigs was only distantly related to Influenza C viruses circulating among humans. Transmission of Influenza C virus between humans and pigs has occurred in the past[3].

It was long thought that Influenza C virus was an infectious agent that only affected humans. Even influential (and expensive) textbooks as late as 1990, like ‘Applied Virology: Volume 2 Research Virus Variability, Epidemiology and Control’, were certain that humans were the only natural reservoir of the virus. I wonder what people were thinking if you consider the insidious nature of all Influenza viruses.

[From: 'Applied Virology' - 1990]

And pigs weren’t the only animals that could become infected with Influenza C virus. It was detected in cattle and in mongrel dogs[4].

[1] Guo et al: Isolation of Influenza C Virus from Pigs and Experimental Infection of Pigs with Influenza C Virus in Journal of General Virology - 1982
[2] Yuanji et al: Genome analysis of influenza C viruses isolated in 1981/82 from pigs in China in Journal of General Virology -1984
[3] Kimura et al: Interspecies transmission of influenza C virus between humans and pigs in Virus Research - 1997
[4] Ohwada et al: Distribution of the antibody to influenza C virus in dogs and pigs in Yamagata Prefecture, Japan in Microbiology and Immunology - 1987