Why Don’t Cats and Dogs Get Human Viruses?

Dear Lowdown:

Can cats and dogs contract the same viruses as humans?

- Allie Lee (Chicago)



Dear Allie:

Do you remember that old wives tale? The one that says cats can steal the breath of babies while they are sleeping? Well there is some truth behind it. Some viruses can be spread from cats, and other domesticated animals, to humans, and vise versa. But wait, before you go telling your great Aunt Marian that she was right to feint from terror when she saw your cat Ben sleeping on your baby brother’s chest, you should know that, due to the differences in the genetic makeup of viruses that affect human and animal immune systems, the instances in which viruses are spread this way are rare. What you should be worried about is how viruses are spread within the animal community, and our community as well.

Viruses are tiny organisms that are made up of strands of DNA. The codes within the DNA of the virus determine whom they can affect. Unlike other cells, viruses cannot survive or reproduce without a host of living cells. Viruses can infect a host cell through two different processes. They can either choose to kill their host cell, or, if they are nice, to quietly live inside the cell until the cell dies of natural causes.

The first method occurs when a virus attaches itself to the outside of the host cell, drills a hole into the cells membrane, and implants part of its genetic material into the host cell. The genetic material grows inside the cell, and creates thousands of copies of the virus that then, due to lack of room within the cell, burst through the host cell’s membrane, effectively killing the cell (“Science Clarified”).

You’ve seen alien right? Imagine that, but instead of one alien bursting out of a woman’s stomach, imagine thousands of tiny little aliens bursting out of every part of the woman’s body. Lovely, isn’t it?

The second method is a lot less gruesome, but far more invasive. The virus inserts itself into the host cell, and combines its genetic material with that of the host cell. The virus can then make thousands of copies of itself through the cell’s own reproductive process of mitosis (“Science Clarified”).

It is very rare for a human to contract a fatal virus from a dog or a cat or visa versa. Dogs and cats cannot catch human colds due to the fact that the viruses that affect us and the viruses that affect animals usually have a different genetic sequence from each other. The differences in DNA make it impossible for a virus that is commonly found in humans to be hosted by an animal’s cell, due to the fact that the animal’s immune system would recognize the presence of a foreign body.
Think of our viruses and animal viruses as two different species. These two species don't just look different, but are genetically different. Oh. And they hate each other. Now imagine what would happen if an animal virus decides to go live in an area that is completely populated by human viruses. If you can’t imagine, let’s just say that the virus will no longer be infecting innocent animals.

This however, does not mean that humans and animals cannot contract viruses from each other. They can, and when they do, the viruses are often very potent. The most common viruses in both humans and animals is the flu. The flu is caused by multiple strains of the same virus, and is capable of mutating, which not only causes problems for us, but also for our pets (“CDC”).

Type A flu is the most common flu, and is found in both humans and animal, and some strands of the virus can be transferred from either host. This occurs when an animal variation of the flu mixes with a human variation of the flu.

For example, the pig is susceptible to both human and avian flu (avian flu is used to describe Type A flu found in most animals) and can therefore act as a breeding ground for mutating flu viruses. When a pig contracts both a human flu and an avian flu simultaneously the flu viruses combine together to form a new strain of the flu virus (“CDC”). This flu virus is like the super villain of viruses. Not only does it have the characteristics of both human and avian flu - which makes it capable of infecting humans and animals - but also it is virtually impossible to vaccinate against due to the fact that there is no other strain like it. This happened last year when the H1N1 flu virus was created from a mutation formed from avian, swine, and human flu.

The flu is not the only virus that we can catch from animals. Our pets carry numerous viruses and infectious diseases that can be harmful to us. These viruses are usually transmitted through saliva or scratches. So the next time you’re letting Fluffy lick your cut to “clean it,” please, don’t.
Dogs and cats also have a wide variety of viruses that can only affect their immune systems, and they are as varied as the viruses that affect us. Lucky them. Some of the more fatal ones are: rabies and kennel cough in dogs, and feline leukemia and Calici in cats.

Rabies is a virus that is transmitted through saliva. Once a dog is infected with rabies the virus attacks the nervous system, and this is what makes the dog foam at the mouth and act abnormally. This is not to be confused with your dad spraying whipped cream on you dog’s face to freak out your mother. Rabies is one of the few fatal viruses that can be spread to humans through saliva. Kennel Cough is to dogs as the common cold is to humans. The virus is spread through contact with infected dogs, and is most dangerous to puppies because it can suppress the immune system (“Dog Owner’s Guide”).

Feline leukemia is almost exactly the same as leukemia in humans, except for the fact that Feline leukemia is contagious. It is caused by a virus, which mutates to form cancerous cells. The virus is spread through urine, spit, and other fun stuff (“Pet Place”). This animal strain of leukemia is an example of a viral strain that cannot be contracted by humans.

Calici is one of the most fatal diseases in cats, due to the fact that humans can act as “carriers,” spreading the virus to other cats. If a person comes in contact with the virus, they can spread it by touching another cat. The virus causes an upper respiratory infection that weakens the immune system, and can ultimately lead to a fatal case of pneumonia (“CFA”).

With today’s technology most viruses, animal and human, can be prevented with vaccinations. Bodies are protected from infection by disease-fighting cells called antibodies. An antibody can only attack a virus that it recognizes. Vaccinations work by exposing an immune system to a small amount of the virus. This enables your immune system to build up antibodies that recognize the virus’ DNA, so your body can defend itself if the virus is contracted. Think of antibodies as soldiers; really dumb soldiers that can only attack if they recognize the person that they are about to kill.

Vaccinations for both humans and animals are not required by law. In fact, the only viruses you are required to vaccinate against is rabies (for your dog of course). Many people choose not to vaccinate their pet because they believe it is harmful. There is a small chance that vaccinating a pet will harm it due to the fact that you are exposing the animal to a miniscule amount of the virus. Parents also often decide not to vaccinate their children against viruses such as the chicken pox and measles, because these vaccines have been linked to an early onset of autism. But, once again, the chance of this occurring is very small.

By choosing not to vaccinate their animals and children, pet owners and parents are not only putting their children at risk of infection, but also other children. When a child who is not vaccinated goes out in public he cannot only contract the virus, but can also act as carrier and spread the virus throughout his community. For instance, the measles, which used to be under control, has reached almost endemic proportions in communities throughout America, due to the fact that parents refuse to vaccinate their children. This is also the case for feline leukemia, which, due to owners not vaccinating their cats has caused thousands of cats (stray and domestic) to die.

Choosing not to vaccinate also proves problematic during flu season. As mentioned earlier the flu is a very nasty but smart bug that can mutate and infect both humans and animals. By not vaccinating ourselves during flu season we create the ultimate environment for the creation of an invincible flu virus. This is what happened last year with swine flu panic (mentioned earlier), the main cause of last year’s panic was that the Swine Flu virus was much stronger than its cousin the normal flu. Its strength stemmed from the fact that for years preceding the panic many people had become lax in their vaccinations enabling the virus to mutate into a strong almost invincible virus. This will happen again if people do not protect themselves against viruses. Next time, the virus will be even stronger. So if you really want to help prevent the next viral apocalypse, please, vaccinate yourself and your pets.


Sincerely,

Nora Molasky






































Works Cited

1. "Virus." Science Clarified. Advameg Inc., 2010. Web. 14 Nov 2010. .
2. Transition of Influenza Viruses from Animals to People." CDC centers for disease control and prevention. CDC, 2010. Web. 14 Nov 2010. .
3. "Influenza Viruses." CDC centers for disease control and prevention. CDC, 2010. Web. 26 Nov 2010. .
4. "Dog Diseases." Dog Owner's Guide. Canis Major Publications, 2010. Web. 14 Nov 2010. .
5. Lagerwerf, Wilma. "Feline Upper Respiratory Diseases: Calici." CFA cat fancier's association inc. Canis Major Publications, 2010. Web. 14 Nov 2010.
6. Primovic, Debra. "Feline Leukemia Virus." Pet Place. Intelligent Content Corporation, 2010. Web. 26 Nov 2010. .