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We’re bluntly in love with cats. It’s not something we just say – it’s a fact. This is why it's so important for us to keep them healthy and happy for many years to come. Today we will talk about some of the most common viruses in cats, signs of infections and possible vaccinations.
Background information
What are viruses?
A virus is an infectious particle that can only replicate inside a living cell. They can infect all life forms, from microorganisms to animals. A virus consists of the genetic material (DNA or RNA), a protein capsid and a lipid envelope.
Biologists sometimes describe them as "organisms at the edge of life", as they closely resemble living organisms but they don’t have a cellular structure nor their own metabolism and they do not grow through cell division. They infect a host cell, integrate themselves in the cell and redirect the cell to produce their products and multiple copies of themselves.
How do vaccines protect against viruses?
Viral infections in animals cause immune responses. These immune responses can also be provoked by vaccines which help the animal acquire immunity to the specific virus.
Some vaccinations are obligatory by the law and others are not. For some viruses, vaccinations have not been developed or perfected yet. The American Association of Feline Practitioners has grouped vaccines for cats into three general categories:
- Core: all cats should receive the vaccine regardless of circumstances,
- Non-core: recommendation based on risk for exposure to disease (i.e. location and lifestyle),
- Not generally recommended: not recommended due either lack of evidence of effectiveness or a high chance for adverse;
Most common viruses in cats
1. Feline Immunodeficiency Virus (FIV)
Feline Immunodeficiency Virus (FIV) is a lentivirus affecting from 2.5% to 4.4% cats worldwide. FIV is taxonomically different from the other two feline retroviruses, feline leukemia virus (FeLV) and feline foamy virus (FFV) and is more closely related to human immunodeficiency virus (HIV).
FIV is the only lentivirus causing a disease similar to AIDS in non-primates. FIV is not lethal for cats, and they can live relatively healthy as FIV carriers. Vaccines for this virus have been designed, but the vaccination against FIV is classified as "non-core".
FIV is one of the most common viruses in cats, but the vaccination is classified as "non-core"
FIV can compromise the cat’s immune system and it infects many cells including T lymphocytes (specifically CD4+ and CD8+), B lymphocytes and macrophages. Cats can usually handle the disease caused by FIV quite well, and only in 5% of the cases their immune system debilitates and leads to the exhaustion of T-helper cells. In humans, this percentage is much higher and is estimated to be around 50%.
2. Feline Coronavirus (FCoV)
Feline Coronavirus (FCoV) is a positive-stranded RNA virus that causes a fatal, aberrant immune response called Feline infectious peritonitis (FIP) in cats. FCoV is a gastrointestinal virus and the infections are usually asymptomatic or coupled with diarrhea. There are two main forms of FIP: effusive (wet) and non-effusive (dry). While both types are fatal, the effusive form is more common (60–70% of all FIP cases) and progresses more rapidly than the non-effusive form.
The effusive FIP is characterized by the accumulation of fluid in the cat’s abdomen or chest. This leads to breathing difficulties, lack of appetite, fever, diarrhea and weight loss. In non-effusive FIP, the cats show similar symptoms of infection but there are no fluid accumulations. Cats suffering from this type of FIP will often show ocular or neurological signs too. The vaccination against FIP does exist, but it is classified as "not generally recommended".
FCOV is also one of the most common viruses in cats, but the vaccination is classified as "not generally recommended"
3. Feline Leukemia Virus (FeLV)
Feline leukemia virus (FeLV) affects only cats. It is transmitted via saliva or nasal secretion. If not defeated, it can cause a disease that can be lethal. It is categorized into four subgroups: A, B, C and T. Symptoms, prognosis and treatment depend on the subgroups.
The effects of the disease caused by this virus are diverse. The cat can either fight off the infection completely and become immune, it can also be a healthy, unaffected carrier or it can have a compromised immune system. The final stage of the disease is the development of lymphomas. The vaccination is possible and classified as "non-core".
4. Feline Panleukopenia Virus (FPV)
Feline panleukopenia virus (FPV), also referred to as feline distemper, feline ataxia or cat plague is a viral infection caused by feline parvovirus. It affects both domestic and wild cats. Once contracted, it is highly contagious and can be fatal to the affected cats. The name panleukopenia comes from the low white blood cell count (leucocytes) exhibited by affected animals.
Panleukopenia can be spread via bodily fluids, feces or fleas. It primarily attacks the cells of the gastrointestinal tract lining which can further cause sloughing of the intestinal epithelium. This can further lead to diarrhea, dehydration, malnutrition, anemia and even death. The vaccination is classified as "core" and is highly recommended for all cats.
FPV is one of the most common viruses in cats and the vaccinations are "core" and recommended to ALL cats
5. Feline Calicivirus (FCV)
Feline calicivirus (FCV) is one of the two important viruses causing respiratory infections in cats. FCV can be isolated from about 50% of cats with upper respiratory infections. This virus replicates in the oral and respiratory tissues and can be isolated from saliva, urine, respiratory secretions and feces.
The symptoms can occur chronically, acutely or not at all. Acute signs include fever, nasal discharge, sneezing, stomatitis and conjunctivitis. When coupled with bacterial infections, pneumonia can develop too. The FCV can’t be specifically treated, but antibiotics are often used to treat secondary bacterial infections and immune modulators that can sometimes couple the viral infection. The vaccination is classified as "core".
6. Feline Herpesvirus
Feline viral rhinotracheitis (FVR) is an upper respiratory infection caused by the feline herpesvirus. This virus is the second of the two important viruses causing respiratory infections in cats (FCV being the first one). FVR is very contagious and it can cause severe disease, such as lethal pneumonia in kittens.
Feline herpesvirus is transmitted directly and it replicates in the tonsils and nasal and nasopharyngeal tissues. The signs of the infections include coughing, sneezing, nasal discharge, conjunctivitis, lack of appetite and fever. The vaccination against the feline herpesvirus is also classified as "core".
7. Rabies
Rabies is a viral disease caused by lyssaviruses and it is characterized by brain inflammation in humans, cats, dogs and other mammals. The signs can include fever, tingling, violent movements, uncontrolled excitement, aquaphobia, inability to move certain parts of the body, unconsciousness and confusion. If left untreated, this disease nearly always leads to death.
Rabies is one of the most common viruses in cats and it causes devastating and lethal disease. Pet vaccinations against it are legally obligate in some parts of the world, but not everywhere.
Most commonly, rabies is transmitted through a bite from an infected animal. It can also be transmitted if saliva of an infected animal comes in contact with an open wound or mucous membranes of another animal. Unvaccinated cats allowed to go outdoors are at the highest risk for rabies.
"Outdoor cats may, in the course of daily life, get into a fight with an infected wild animal or an infected stray dog or cat. And although widespread vaccination programs have helped to control rabies in dogs, feral cat populations remain a reservoir host for the rabies virus." – explained WebMD.
The most accurate diagnostic test for rabies is the direct fluorescent antibody test. However, this can only be performed when the animal has already deceased. The accurate diagnosis in living animals is a lot more difficult. After incubation, the virus can remain in the cat’s body anywhere from one week to more than a year before it activates itself. Once activated, the signs occur very quickly.
The vaccination against rabies is somewhere classified as "core", somewhere as "non-core", but in some countries it is obligatory.
These were just 7 of the most common viruses diagnosed in cats, among many more that can afflict our pets. Viruses can be very dangerous and it is therefore highly important to regularly vaccinate our cats and protect them from viral infections.
Consult with a veterinarian professional about the vaccination program for your cat. They will advise the recommended vaccines according to your location and your cat's lifestyle.