Cats bring an irreplaceable amount of love and companionship into our lives. Unfortunately, our furriends can sometimes fall ill or become injured for diverse number of reasons. Many of the illnesses commonly diagnosed in cats are caused by viral or bacterial infections.

A virus is an infectious particle that can only replicate inside a living cell. They can infect all life forms, from microorganisms to animal and pose a challenge to the body to defend from because they hide in the cells. For more about viruses please refer to our recent discussion about Some of the Most Common Viruses Afflicting Cats.

Unlike viruses, bacteria are single-celled living organisms, thought to be among the most successful life forms on the planet. While many bacteria are beneficial or simply harmless to most organisms, some are pathogenic and can cause disease in certain hosts. Note: a bacterium that is pathogenic to some organisms or organs, does not have to be pathogenic to others.

What are bacteria?

A bacterium (plural: bacteria) is a prokaryotic, single-celled organism belonging to the domain bacteria. Their cell organisation is quite simple and they do not possess a nucleus nor organelles. Just like us, our pets are constantly exposed to bacteria. The vast majority of the bacteria in and on the feline body are rendered harmless by the immune system.

Many of these bacteria are also beneficial, particularly in the digestive system. However, some bacterial species are pathogenic to cats and can cause infectious diseases. The severity of the infection, as well as the symptoms, diagnosis and treatment are all infection specific.

What is a bacterial infection?

A bacterial infection is an invasion of an organism by disease-causing bacteria (a pathogenic bacterium or pathogen). The pathogen enters the body, obtains nutrients from it, reproduces and causes harm. The body can fight the bacterial infection off with its immune system. Mammalian hosts react to infections with an innate response, often involving inflammation, followed by an adaptive response (Signore, 2013).

An infection can affect any part of the body and in some cases, several. Cats can also occasionally be silent carriers of bacteria too, meaning they can spread the pathogens to other organisms, even if they are not showing symptoms of being sick themselves. There are several risk factors that can help the pathogen invade and harm the host. These involve: cat’s ag, weakened immune system, poor diet, overall feline health status and exposure to pathogenic transmitters.

Bacterial infections commonly diagnosed in cats

There are many different bacteria that can cause disease in felines. Following is a table created by RRDA with an overview of the common bacterial infections in cats:

Bacterial pathogens causing disease in cats most commonly belong to the following genuses: Staphylococcus, Salmonella, Escherichia, Campylobacter, Clostridium, Toxoplasmosis, Chlamydophila, Pyodermas, Actinomyces, Spirochete, Fusobacterium, Bartonella and others. Because of the severity of the disease they cause, three of the most famous species of bacteria pathogenic to cats are Mycoplasma haemofelis, Yersinia pestis and Bartonella henselae.

M. haemofelis is a gram negative bacterium typically spread by fleas and ticks. The disease caused by this bacterium is called feline infectious anemia. Y. pestis is also a Gram-negative bacterium and it causes the disease called plague. B. henselae is a species of Gram-negative bacteria which is responsible for the notorious cat scratching disease that can be transmitted to humans. It is transmitted by ticks, fleas, sand fleas and mosquitoes to cats, or by scratches or bites from cats to humans.

Symptoms of bacterial infections

The symptoms of bacterial infections are always infection specific. This means that the symptoms your cat shows highly depend on the type of the bacterium causing the harm, the organs affected, the severity and stage of the infection and the overall feline health status. Symptoms typically observed in bacterial infections involve: fever, diarrhea, nausea, vomiting, indigestion and lack of appetite, skin abscesses, lesions and wounds, coughing, runny nose and eyes and problems with urinary and respiratory tract.

Diagnosis and treatment

When admitted to the vet’s office, the cat will be physically examined and its medical history and symptoms diary will be reviewed by the veterinarians. Afterwards, when required, the vet might also run blood tests, skin biopsies, sensitivity testing and cultures to confirm the diagnosis. This may also help resolve the cause of the infection.

Depending on the infection and the cat’s health and age, the vet will design the adequate therapy. Treatment of bacterial infections typically involves the antibiotics. It is important to dose the antibiotics as instructed and to do the entire course of treatment as prescribed. Otherwise, the infection may return even worse than before. In case of skin infections, topical medications are prescribed as they help reduce inflammation, skin redness and runny eyes and nose. Additionally, the vet may advise fever and pain medications too.

Bacteria are everywhere around us. Although commonly beneficial, our immune system makes sure to keep the harmful bacteria harmless too. However, sometimes the germs manage to break through and create problems. Are you interested in learning about a particular bacterial infection in detail? Let us know!

Further reading:

1. Alberto Signore (2013). “About inflammation and infection” (PDF). EJNMMI Research. 8 (3).

2. Bacterial Infection in Cats by Wag! A dog´s best friend.

3. Treating Bacterial Infections in Pets by Diamonback drugs.