May 2009

Novel Influenza A H1N1 Virus - Protecting Pigs, Protecting People

There are serious concerns that the novel influenza A type H1N1 virus that has been circulating in Mexico since mid-March 2009 may spread widely and cause an international pandemic.

In a Preliminary Outbreak Assessment Defra have concluded that is a negligible likelihood of introducing human influenza strain H1N1 to the UK by the legal import of pigs or pig products from North America. However, in the Assessment it is pointed out that it is possible that an infectious human, returning to the UK, could introduce a new strain to the pig population.

As pigs in the UK appear free of this strain of H1N1, the aim must be to keep it out of our pigs. It is important to try to prevent people from infecting pigs with influenza strains and with this novel H1N1 strain, in particular.

Pig farmers should be advised to take steps to reduce the risk of people introducing influenza virus strains into their pig herds.

• No-one with flu-like symptoms or who has symptomatic family members should be allowed to contact pigs if it can be avoided.
  
  
• Any potential visitors should be asked about whether they or any family member have had flu-like symptoms in the previous 7 days.
  
  
• It may also be sensible not to allow anyone who has been in Mexico in the previous 7 days to come in contact with pigs.

As the situation will continue to evolve rapidly advice should be kept under review.

Building biosecurity to keep the virus strain out of pig herds is one example of the important role veterinary surgeons play in protecting public health. Please discuss biosecurity with farmers and remind them of the importance of cleaning any equipment that may be shared between farms. Influenza is highly contagious and transmits easily by fomites. While the new variant influenza strain has not been identified in pigs in the UK, we should all be proactive in working to raise biosecurity levels at this time and using this as an opportunity to increase awareness about biosecurity in general.

The surveillance system already in place has been useful to demonstrate that this strain of Influenza A H1N1 is not present in UK pigs. The current surveillance project for Swine Influenza is ongoing. Veterinary surgeons should remain on alert for suspicious cases involving pigs exhibiting influenza-like clinical signs. If there are any suspicions of influenza in pigs please contact your regional veterinary laboratory and arrange to submit diagnostic samples (pigs, plucks, tissues (tonsil, trachea, lung) or nasal swabs) from acutely-ill, febrile pigs. Note that post-mortem examinations will be charged at the normal subsidized rate. Appropriate samples submitted solely for Swine Influenza testing will be tested free of charge by VLA and SAC.

The quality of samples is very important and it is recommended that trachea/lung samples taken on the farm are taken by a vet and transported to VLA in appropriate media. Vets should contact their regional veterinary laboratory for advice on sample submission. Tissue samples are preferred to serology samples. In a live pig, nasal swabs can be performed. Serology testing for influenza is not free.

Submission of live or freshly dead/euthanased pigs or plucks is preferred as this allows differential diagnosis and comprehensive testing including immunohistochemistry for swine influenza if histopathology is suggestive of influenza infection. Vigilance in enhancing surveillance demonstrating continued freedom of our pig herds from the novel strain of H1N1 builds confidence and further demonstrates our commitment to protecting public health.

This strain of influenza virus appears to be a recombinant of human, swine and avian viruses. This strain has never been isolated from pigs. There have been no reports of unusual disease in pig herds in Mexico. It is not even clear at this stage if this strain of virus can infect and cause disease in pigs.

Results of surveillance suggest that this variant of H1N1 does not appear to be present in pigs in the UK or anywhere else in the EU. The import of live pigs and pig products from Mexico is not permitted within the EU.

The World Health Organisation has made it clear that there is not a food safety risk to consumers from this novel strain of influenza H1NI. The European Food Safety Authority (EFSA) has stated that it is not aware of any scientific evidence to suggest that influenza viruses can be transmitted to humans through the consumption of meat such as pork and pork products. In general, influenza viruses affect the respiratory tract and the usual way of transmission is through direct contact or close proximity with affected individuals or animals.

The situation continues to evolve rapidly and there are links to further information below:

Defra: http://www.defra.gov.uk/animalh/diseases/swine-flu/index.htm or follow links from the homepage www.defra.gov.uk
NHS: http://www.nhs.uk/AlertsEmergencies/Pages/Pandemicflualert.aspx or follow links from the homepage www.nhs.uk
HPA: http://www.hpa.org.uk/webw/HPAweb&Page&HPAwebAutoListName/Page/1240732817665?p=1240732817665 or follow links from the homepage www.hpa.org.uk
WHO: http://www.who.int/csr/disease/swineflu/en/index.html or follow links from the homepage www.who.int/en/
EC DG SANCO: http://ec.europa.eu/health/ph_threats/com/Influenza/novelflu_en.htm or follow links from the homepage http://ec.europa.eu/dgs/health_consumer/index_en.htm
ECDC: http://ecdc.europa.eu/en/
CDC: http://www.cdc.gov/swineflu/ or follow links from the homepage www.cdc.gov