As a self-proclaimed “cat lady” I decided that the recent confirmation of the transmission of the H1N1 influenza virus from humans to cats is appropriate to blog about. On November 4, 2009, it was reported and confirmed that a 13-year old cat in Iowa contracted the H1N1 influenza virus. Since then, more cats have been diagnosed with H1N1 and there has been one presumed, yet not confirmed, death.
When two members of an Ames, Iowa, family came down with the H1N1 flu, the family pet, a 16-pound orange tabby, became lethargic, lost his appetite, and was showing signs of respiratory discomfort. Fortunately they were able to call a family friend, Dr. Brett A. Sponseller, who is a specialist in large animal internal medicine and molecular virology at the College of Veterinary Medicine at Iowa State University. Dr. Sponseller and his colleague Dr. Albert Jergens conducted many tests and concluded that the cat indeed had H1N1 influenza.
This story is unique because it is the first case of a feline contracting influenza from a human, which has created concern for health officials and pet owners alike. There have been cases of companion animals acquiring the flu from other species. The canine influenza (H3N8) began in horses, and cats have been known to contract avian influenza (H5N1) from eating birds. However, the feline H1N1 case in Iowa remains the first time a cat has contracted influenza from a human. To date this virus has been confirmed in three pet ferrets, turkeys in Chile and Canada, and has also been transmitted between humans and pigs.
Since then, there have been more confirmed cat H1N1 cases. On November 17th 2009, a cat in Park City, Utah became the second confirmed H1N1 feline case. The owner contracted the H1N1 flu and noticed flu-like symptoms in the cat – similar to the Ames family. On November 18th, 2009, the Oregon State public health veterinarian reported that a pet cat died from presumed H1N1 influenza virus infection approximately one week after a child in the household had flu-like symptoms. The cat shared a household with three other cats – all of which became ill with less severe sneezing and coughing symptoms.
Even though veterinarians and health care officials are uncertain of how the cats contracted the virus, it is known that the flu is easily transmitted between family members, and it is not surprising that a sociable cat would come into contact with the virus making it more susceptible. It is important to note that according to Dr. Sponseller, there is no evidence that a cat can transfer the H1N1 virus to a person because cats with flu typically don’t cough or sneeze.
This situation has fostered more “swine” flu panic and has raised many questions. How can a cat get H1N1 from humans? What makes this influenza virus transmittable to cats? Can a cat transfer H1N1 to humans? Can other companion animals such as dogs get H1N1? Will there be a H1N1 vaccine for pets? Until more is learned about the transmission of the H1N1 influenza virus, many of these questions will remain unanswered.
Parker-Pope, Tara, “The Cat Who Got Swine.” The New York Times. The New York Times Company. November 5th, 2009. Web. November 17th, 2009. <http://well.blogs.nytimes.com/2009/11/05/the-cat-who-got-swine-flu>.
“2009 H1N1 Flu Virus Outbreak” AVMA. American Veterinary Medical Association. November 18th, 2009. Web. November 20th, 2009. <http://www.avma.org/public_health/influenza/new_virus/>.
I'm so glad you did decide to blog about it! Actually, the topic is of great immunological significance. Emerging viruses tend to arise from this jumping between species. Zoonoses is responsible for AIDS and Ebola just to name a few of the most sensational. The viruses are often more virulent and often deadly in the new host because they have not had time to adjust to the foreign environment to maximze their ability to persist. (Killing off their host to fast can end in a self limiting infection.)
ReplyDeleteViruses evolve to persist either in a population or in the specific host. An acute virus flu maintains in the population by antigenic drift and shift. Not only does it persistent by point mutations that lead to avoidance of immune recognition but it also exchanges sections of its genome when coinfecting with another strain.
This leads me to the point. If H1N1 Is jumping to cats, not only is it more deadly for the cat, but now the virus has another host where it can combine with say an avian flu to create a more dangerous strain for humans when it makes the jump back. Although you mention the flu is not transmitted back to humans, I am a bit skeptical of the reasoning. I have certainly seen a cat sneeze! Because cats are such an intimate part of some of our lives this does pose a threat as the virus evolves.
I recently heard cats are not the only reported pets, ferrets are as well. I am unsure about cats but I do know that for like avian influenza some of the animal models for vaccine's were conducted in ferrets because the respiratory tract etc. Anyone know anything more about this? Are cats more susceptible to human respiratory illness?
ReplyDeleteThis article is a perfect example on how serious viruses are. We have a fairly new virus that we really don't know a lot of information about until its too late. The H1N1 flu has now been able to jump from one species to another. This in my opinion is a scary thing. It shows that no matter how long we study something and finally get an idea of how things work, we get a curve ball thrown at us. Thanks for posting this article.
ReplyDeleteIt would be interesting to see what makes the H1N1 different then other influenzas. Maybe that would tell us why the virus is able to jump from one species to another. They should have some idea already, since the vaccine is now available.
ReplyDeleteThanks for all your comments! This is exactly why I posted this article because it signifies the severity of the H1N1 virus. JPerkins - that is a very interesting correlation. I am too skeptical about the reasoning for the virus being unable to be transmitted back to humans. Just recently both of my cats have had severe sneezing and respiratory symptoms (it turned out they had an upper respiratory infection). In regards to TanyaC's question, I learned that although cats aren't usually susceptible to human respiratory illness they are extremely contagious among their species and it's extremely difficult to prevent it from spreading! With this knowledge, it is very scary considering not much is known about why or how cats get H1N1 virus and whether or not it can be transmitted to other common household pets such as dogs or even back to humans. I'm hoping that this is something that the scientific community is working very hard to figure out. If I find any more information on this I will most definitely update the blog.
ReplyDeleteIn response to HollyM, influenza's tropism is primarily defined by the cleavage of hemagglutinin (HA or the "H" in H1N1) and its binding to cells that express appropriate receptors. Some HA can only be cleaved by proteases expressed in the respiratory tract, restricting the tissues that can be infecting and (generally) resulting in milder disease. However, it is known that different HA's preferentially bind in the upper respiratory tract (throat, nose mouth) or the lower respiratory tract, because of the different receptors expressed by cells in these areas. This further defines the tropism of the virus.
ReplyDeleteTo finally get to your question about species jumping, some species express receptors that bind the HA of influenza viruses. Other species may not. Cats might not express those receptors in lower respiratory tract like in humans and consequently experience a very different infection. Virus transmission is more complicated than I have outlined but you could imagine that if H1N1 normally infects the lower respiratory tract of humans, which may be similar to the respiratory tract of cats (as far as HA binding is concerned), the virus might be "cross-infective".
As far as why cats are more likely to be infected by humans than humans by cats- it is more likely that if I sneeze or cough and cover my mouth with my hand I will expose the cat to that (by petting it later and the cat then bathes itself with its tongue introducing the virus into the respiratory tract) than that the cat will sneeze directly into my face. I do agree that it isn't impossible, but it would make sense from what we know of human-human flu transmission to assume that infected cats won't infect us as often as a human does (there isn't as much hand shaking between cats and humans as humans and humans) especially if there is a difference in respiratory tropism for the virus between the species.
The canine influenza virus was identified in 2004 when the H3N8 virus jumped from horses to dogs. In June of 2009 a vaccine has become available, so although it is scary researchers are keeping up with the new viruses.
ReplyDelete