There is no evidence that Swine Influenza (SI) occurs in pigs in South Africa, says Dr Peter Evans of SAPPO. Reacting to media reports he says that his statement is based on not finding antibodies to SI during numerous country-wide serologic surveys. “Most commercial farms (where SI is most likely to be found), get regular clinical evaluations by veterinarians.
“Classical Swine Influenza in pigs is caused by a subtype of the influenza virus called H1N1 (a member of the A type influenza viruses). Human influenza can be caused by a H1N1 subtype that is genotypically distinct from the pig H1N1. This leads to confusion in reporting, assuming that humans have been infected with Swine Influenza Virus (SIV) genotype.
“It is important to be cognisant of the fact that people in close contact with pigs for long periods of time can occasionally be infected by the pig influenza virus but importantly, there is no evidence that having been infected, that these people can pass the virus on to another human,” Dr Evans says.
“Pigs can be infected by human influenza viruses and will develop antibodies but will never get ill. Pigs also readily get infected by avian and other mammalian strains of influenza. Different influenza strains will ‘share’ their genetic material during multiplication, which leads to a ‘new’ different flu virus occurring. This process happens readily in pigs and especially where people, pigs and birds are in close proximity. This is one of the reasons for pig producers to never have other animal species or birds in their piggeries.
“Investigation of the H1N1(09) outbreak in humans in Mexico and the USA in 2009, determined that the virus had some pig proteins, but was mostly a human genotype. Although this outbreak was sensationalised as ‘swine flu’ the evidence was that it was a human variant and had very little to do with pigs.
“Swine influenza does not spread via meat. In countries that have influenza no abattoir workers or pork processors have ever tested positive for antibodies. Pork is safe,” Dr Evans stresses.