22 July 2009

This advice is provided by NSW DPI for veterinarians who work with pigs. It addresses the recognition, diagnosis and implications of influenza, including the 2009 strain of influenza known as Pandemic A H1N1 2009, or 'Human Swine Flu', in pigs.

What is Pandemic H1N1 2009?

A new strain of influenza apparently originating from North America, has now been detected in humans in Australia. This new strain has been identified as Type A, H1N1, and includes genetic material from strains of influenza isolated from pigs in North America and Eurasia. It also includes genetic material from human and avian influenza viruses.

Can Pandemic H1N1 2009 spread from people to pigs and from pig to pig?

It is quite possible Pandemic H1N1 2009 can spread from an infected person to a herd of pigs. There is certainly experimental evidence showing that pigs shed Pandemic H1N1 2009 virus for up to 10 days post-infection, and that infection can spread from infected to susceptible pigs

What precautions should I take to prevent influenza spread?

Most types of influenza viruses, can be transmitted between pigs and people. Influenza viruses are generally spread via contact between a susceptible human/animal and an infected human/animal - usually via droplets and aerosols (sneezing, coughing). The following precautions will reduce the likelihood of spreading influenza to pigs:

• Do not visit farms unannounced.
• Adhere to the farm’s biosecurity standards.
• If you’ve experienced any symptoms of influenza, avoid contact with pigs until 14 days after the onset of those symptoms.
• Wash your hands carefully before and after handling pigs.
• Wear farm-specific boots and overalls when visiting farms.
• Wear cleaned, disinfected boots and freshly laundered clothes on entry if the farm does not provide protective clothing.
• Dispose of used tissues in a rubbish bin away from pigs' access.
• Do not eat, drink or smoke whilst in contact with pigs.
• Wearing gloves reduces the risk of transmitting influenza virus from hands to pigs.
• Clean and disinfect equipment, e.g. ear muffs, necropsy kits, ultrasounds, before and after each farm visit.
  

What are the clinical signs of influenza in pigs?

The incubation period of influenza in pigs is very short, as little as 12-48 hours, and the onset is usually rapid and dramatic.

If any strain of influenza was introduced into pigs in Australia, it would result in animals of all ages becoming sick in a short space of time. The key clinical signs to look for include:

• New or unusual disease signs, previously not seen.
• When the virus first enters the herd, two or three animals may be observed sick for the first two days, followed by:
  • rapid spread of the disease, with many animals becoming infected;
  • fever (>39°C), inappetence, huddling and depression;
  • a range of respiratory signs including coughing and sneezing with discharge from the nose and eyes;
  • pregnant sows may abort due to the fever.
• Acute respiratory distress is likely to persist over a period of 7-10 days (depending on the amount of contact between groups of pigs).
• Most affected pigs will look as if they are going to die but most of them survive without treatment, unless the herd already has a respiratory disease problem.
• Influenza causes severe pneumonia on its own but when it is combined with other infections such as Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and Haemophilus parasuis, an intractable chronic respiratory disease syndrome can develop. Severely affected individuals or groups of pigs are therefore best given antibiotic cover to prevent secondary pneumonias from developing.
• Once the disease becomes endemic in the herd, it may be responsible for continuing respiratory disease episodes with symptoms as in acute disease but less dramatic.

What should I do if I suspect pigs have swine influenza?

Immediately phone the Emergency Animal Disease Watch Hotline 1800 675 888. You will be put into contact with a NSW DPI biosecurity veterinarian who will give you detailed advice on how to proceed.

How do I confirm a diagnosis of influenza in pigs?

This can often be made reliably on clinical grounds when the disease is acute, because there are no other diseases that are so dramatic in their onset and clinical effects. No other disease affects so many pigs so quickly.

For confirmation, you should collect nasal swabs from as many affected animals as possible, ideally up to 20. Use dry swabs (not those with transport media for isolating bacteria). Swab both nostrils of each pig sampled (using a different swab for each nostril). Break off the swab and aseptically place it in the transport media (Phosphate-buffered gelatine saline). Both swabs from the one pig can be stored in one vial of transport media. Transport media can be stored in the freezer prior to use.

Swabs and transport media are available from the Virology Laboratory at Elizabeth MacArthur Agricultural Institute (address below).

Collect blood in plain tubes from affected pigs for antibody testing.

Collect duplicate samples from each pig. That way, the virology lab in NSW can send the duplicates to the Australian Animal Health Laboratory (AAHL) in Geelong.

Package swabs and blood in 2 plastic bags (double-bag) and send overnight on cooler or freezer bricks to:

Virology Laboratory
Elizabeth Macarthur Agricultural Institute
NSW Department of Primary Industries
Woodbridge Rd
Menangle NSW 2568

Questions regarding this advice should be directed to:

Dr Trish Holyoake BVSc PhD CMAVA
Pig Health Veterinarian
Wagga Wagga Agricultural Institute
trish.harvey.holyoake@dpi.nsw.gov.au
Ph. 0419 231 534