How Do Indoor Cats Get a Cold? Understanding the Causes and Prevention
Cat owners often think keeping their pets indoors will protect them from illness, but did you know that indoor cats can still catch colds? Yep, even cats with no exposure to other cats can succumb to upper respiratory infections.
So, exactly how do indoor cats get a cold? Well, it’s time to unravel the mystery behind indoor cat colds. I’ll cover the causes, symptoms, and treatment options available. By the end, you’ll understand how your faithful feline got sick and what to expect in the future.
Causes of Colds in Cats
Before we discuss how an indoor cat catches a cold, let’s talk about the causes of colds in cats. As you might expect, just like in humans, there are a variety of viruses and bacteria that can lead to upper respiratory infections (URI) in our feline companions.
The two most common upper respiratory viruses in cats are Feline herpesvirus-1 (FHV1) and Feline calicivirus (FCV). Both of these viruses are widespread in the cat population.
Since they cause similar symptoms, it’s nearly impossible to tell the two apart without laboratory testing. These viruses are spread in the nasal, respiratory and eye secretions and are passed mostly by close contact between cats. These viruses are not contagious to humans.
Although viral infections are the most common cause of URI in cats, there are a few bacterial causes to consider. Primary bacterial upper respiratory infection is caused directly by that infectious bacteria. Organisms that affect cats include Chlamydia felis (Cf) and Bordetella bronchiseptica (Bb).
While Bb causes similar respiratory symptoms to the viruses mentioned earlier, Cf causes mostly eye symptoms. Both are spread by close contact with infected cats. Bb can be passed to dogs and, rarely, to humans. There have been rare reports of humans getting Cf from cats.
Finally, cats with viral URI often develop secondary bacterial sinus infections. Bacteria that normally don’t cause a problem can grow out of control due to damage caused by the virus.
It is not unusual to see cats infected with more than one of these organisms. Your veterinarian may want to do diagnostic testing to identify which organisms are present in your symptomatic cat.
Symptoms of Cat Upper Respiratory Infection
Just so we’re all clear on what a URI is, let’s talk about typical symptoms. Clinical signs can vary from mild, occasional sneezing to severe eye and sinus lesions. Here are some of the symptoms you might see in a sick cat:
- Watery, red eyes
- Swollen conjunctiva
- Crusting around eyes
- Watery, blood-tinged or thick nasal discharge
- Nasal congestion and noisy breathing
- Exaggerated swallowing
- Open-mouth breathing
- Mouth or lip ulcers
- Eating less
How Do Indoor Cats Get a Cold?
It seems like a cruel twist of fate that a cat who lives strictly indoors can still get a cold. How can that happen when they never have contact with other cats?
The number one reason indoor cats get colds is the re-emergence of Feline Herpesvirus. Even years after a cat recovers from an initial FHV1 infection, particles of the virus hide out in their nerves. During times of stress, the dormant virus can re-emerge and cause URI symptoms.
Less common causes of colds in indoor cats include transmission by fomites. That means a person or object passes virus particles from a sick cat. For example, if you visit a friend who has a sneezing newly adopted kitten, you could carry the virus home to your cat if you’re not careful. You can avoid this by washing your hands and changing your clothes as soon as you get home.
Theoretically, your cat could catch a cold from an outdoor cat through an open window. To transmit the virus, the outdoor cat would need to be very close, five feet or less. So this way of getting infected is possible, but not very likely for most cats.
Finally, in homes with multiple cats, one of them might be shedding the virus even though they don’t show any symptoms. Some multi-cat homes have ongoing issues with cats passing the virus back and forth.
Risk factors for Recurrent or Chronic URI in Cats
Stress is a major factor in a cat’s ability to fight off and recover from infectious diseases. It can come in the form of new people in the home, favorite people being absent, having other diseases like kidney problems, surgery, boarding and grooming. But sometimes there is no source of stress that is obvious to us humans.
Stressed cats make extra hormones to boost immunity temporarily. After a while, this effect becomes detrimental as some white blood cells are decreased by long-term stress hormones. One study found that stressed shelter cats were 5.6 times more likely to contract an upper respiratory infection than unstressed cats in the same shelter. (5)
Age plays a role in a cat’s susceptibility to URI. The very young may lack immunity from their mother or vaccination. (4) Very old cats’ immune systems are often not as strong as they once were.
Environmental factors can add to a cat’s stress level. The main concern is the overcrowding of animals in a shelter situation. However, poor air quality, poor nutrition and extreme temperatures can cause physical stress even in single-cat households.
For unknown reasons, cat breeds with short faces such as Persians and Himalayans have an increased risk of developing chronic URI. They may constantly have a bit of a runny nose that flares up into a green snotty nose from time to time.
Cats with compromised immune systems are more susceptible to an initial viral infection. They’re also more likely to have viral reactivation or chronic URI. Immune-compromising diseases caused by Feline Immunodeficiency Virus or Feline Leukemia Virus put a cat at risk. Immune-suppressive drugs such as cyclosporine and prednisone also increase a cat’s risk of URI.
Treatment and When to See a Veterinarian
When your indoor cat starts showing mild URI symptoms like a runny nose or sneezing, watch them closely for other symptoms. Cats with only mild symptoms but who are still eating and drinking can often be monitored without treatment. Most cats get over their cold within 7 days or so.
Here are some signs that a cat’s cold has become more serious:
- Nasal discharge changes from transparent to opaque/green/yellow/reddish
- Poor appetite
- Significant lethargy
- Trouble breathing
If you notice these or any other symptoms you’re concerned about, it’s time to see a veterinarian. Veterinary care in cases like this usually includes supportive care to make sure the kitty is hydrated, warm and nourished. They might also get some nose or eye drops to ease their discomfort.
In some cases, a vet will prescribe antiviral medication and/or antibiotics. Just remember that antibiotics don’t do anything to fight viruses. They’re only effective against bacteria so don’t be surprised if your vet doesn’t prescribe them.
What to Expect in the Future
Once your cat recovers from their cold, cats with low-risk factors may never have another episode. A few cats will have a flare-up of symptoms from time to time.
Some cats develop chronic sinusitis, especially if they experienced severe sinus inflammation or have other significant risk factors.
You can help your cat avoid URI flare-ups by minimizing their exposure to stress. Some people give their cats l-Lysine supplements during stressful times. This amino acid is well-tolerated and may keep FHV1 from activating. (3) Ask your vet if it would be appropriate for your cat.
Cats that live indoors are still susceptible to upper respiratory infections, even if they have no exposure to other cats. Indoor cats can get colds due to the re-emergence of feline herpesvirus-1, transmission by fomites or through open windows, or from another cat in the house that is shedding the virus without showing symptoms.
Other factors that increase a cat’s risk of recurrent or chronic upper respiratory infections include stress, age, environmental factors, and genetics. Symptoms include watery, red eyes, sneezing, and nasal congestion.
- Bannasch, M. J., & Foley, J. E. (2005). Epidemiologic evaluation of multiple respiratory pathogens in cats in animal shelters. Journal of Feline Medicine & Surgery, 7(2), 109-119.
- Berger, A., Willi, B., Meli, M. L., Boretti, F. S., Hartnack, S., Dreyfus, A., … & Hofmann-Lehmann, R. (2015). Feline calicivirus and other respiratory pathogens in cats with Feline calicivirus-related symptoms and in clinically healthy cats in Switzerland. BMC veterinary research, 11(1), 1-12.
- Litster, A. L., BVSc, PhD, FANZCVS, MMedSci. (n.d.). Treatment of Infectious Upper Respiratory Tract Disease: An Evidence-Based Approach. American Association of Feline Practitioners Conference 2017, Denver, Colorado, United States of America.
- Munks, M. W., Montoya, A. M., Pywell, C. M., Talmage, G., Forssen, A., Campbell, T. L., … & Marrack, P. (2017). The domestic cat antibody response to feline herpesvirus-1 increases with age. Veterinary immunology and immunopathology, 188, 65-70.
- Tanaka, A., Wagner, D. C., Kass, P. H., & Hurley, K. F. (2012). Associations among weight loss, stress, and upper respiratory tract infection in shelter cats. Journal of the American Veterinary Medical Association, 240(5), 570–576.