Taking illness to bed: the Influenza tale

As  CCAH many team members and pets are having acute illnesses this time of year, let's chat about infections such as Influenza. 

Did you know that pets, birds, and pigs share some infections in common? Bird flu, Spanish flu, canine influenza, and swine flu among others seem to frequent the news.  The influenza virus, especially, is constantly mutating, so new strain threats to our public health occur yearly. Here's some answers to a few questions I am asked frequently.

At times it seems like “alphabet soup!” What is the meaning of the multiple acronyms for “influenza”?

There are 3  main types of flu named after their core proteins: A, B, and C. The most common form that is a yearly presence is Type A. Influenza B is less frequent, occurring every 2 to 4 years. The remaining Type C is much milder and is not reported to be of an epidemic nature.

IF YOU DON'T WANT TO HEAR ALL THE SCIENCE BEHIND THE FLU, SKIP THIS NEXT PART. IF YOU ARE A SCIENCE GEEK LIKE ME, READ ON... 

There is a lot of the confusion about the different Influenza A  strains and their designation. The designation comes from the numbers tacked onto the surface proteins of the virus: HA (hemagglutinin) and NA (neuraminidase).  HA , a glycoprotein, binds the virus to cells in the upper respiratory tract and ultimately invades the cell, becoming part of its working function. NA, is an enzyme that enhances the flu virus to replicate within host cells and ultimately allows the virus to be released, thus spreading the virus to other cells in the body as it lowers host cell defenses.

The most common 3 types of HA (H1,H2,H3) and 2 types of NA(N1,N2) cause most of the annual influenza(flu) epidemics.  The 2009 infection, H1N1, infected 24% of the world population in a novel mix of human, bird, and swine flu virus particles  with over 200,000 people (mainly children age 5-19) dying.  In traditional seasonal flu, it is mainly the elderly people that succumb to the virus. Some new variants of H3N2v have been seen in children under that age of 10 often with exposure to pigs at state fairs.

Why does it seem most flu viruses originate in Southeast Asia?

One theory is that for many families, pigs, chickens, and people live in close quarters. The virus particles can more easily interchange and mutate. For example, in 2013 it is speculated that a mutation of bird (avian) influenza (H7N9) emerged outside of Shanghai, China. Of the known 101 people infected, 20% died.  This virus H7N9 can also infect songbirds ( a big passion in China) and migratory birds such as sparrows. Most bird flu (H5N1) spreads from birds to people, not person to person. Pigs (swine) are often a common denominator here as they can become infected by bird, human, and swine viruses. They then serve as a conduit to spread bird viruses to people.  The "virus stew” or new combinations of influenza develop when two different flu strains infect a body cell at the same time and reformulate.

Can influenza infect cats and dogs?  

 H9N2 virus is documented to infect dogs and cats (in China )  and it is speculated that pets that pets can further spread this form of the infection.  In 2009 there were 13 cats documented to be infected with the H1N1 virus from their sick owners. Although at this time it appears a low risk, further research is needed.

What is Canine influenza and how is it identified? Can it be prevented?

 H3N8 equine influenza virus (documented for over 40 yrs.) was identified  in 2004 in Greyhounds  housed close to racetracks and is a probable mutation of the  equine virus particles. It can be a catastrophic respiratory problem in boarding kennels and difficult to control without effective hygiene.   Viral particle testing  (PCR of nasal swab) from the respiratory secretions at time of  onset of symptoms is recommended. Alternatively, antibody blood testing initially and then 3 weeks later are the standard for identification of an outbreak.

There is a canine influenza vaccine available. It does not prevent the infection; rather,  it lowers the severity of the disease once a dog is exposed. There is no documented  risk of spreading to people.

What are the current drugs available to fight back the influenza virus?

The current drug strategies are zanamivir (Relenza) and oseltamivir (Tamiflu). These medications and block the activity of NA (neuramidase) and thus hinder its essential role in viral release. Due to their extensive use for people, the cost and availability of these medications has led to limited use in pets. As a side note, for those familiar with canine parvo virus (a horrible intestinal infection of young dogs), Tamiflu has for some shortened the course of the illness in shelters. Antibiotics play no role in treating primary viral infections, but they are helpful in onset of secondary bacterial infections.