Can a Routine Vet Medication Actually Make Your Cat Ill?

What is Fvrcp?

Fvrcp, or feline viral rhinotracheitis, is a common cat virus that affects respiratory system of felines. Fvrcp is a type of herpesvirus and is also sometimes known as feline herpesvirus type 1 (FHV-1) or feline rhinotracheitis virus. This virus is a highly contagious infectious disease affecting cats and can be spread easily from cat to cat (1).

The FHV-1 virus is typically transmitted through direct contact between cats, via airborne respiratory secretions, saliva, and nasal discharges. Cats can spread the virus through actions like sneezing, coughing, nuzzling, or sharing food bowls and litter boxes. The virus can also be spread indirectly by people transferring respiratory secretions on their hands or clothing after handling an infected cat. In some cases, feline herpesvirus can be spread from mother cat to kittens in-utero or from queen to kittens while nursing (2).

Symptoms of Fvrcp

The most common symptoms of Fvrcp in cats include:

  • Sneezing – Cats with Fvrcp often experience sudden and severe sneezing attacks.
  • Nasal discharge – Thick nasal discharge is common, ranging from clear to yellow-green in color.
  • Conjunctivitis – Inflammation of the membranes around the eyes leads to reddened eyes, eye discharge, and excessive blinking.
  • Oral ulcers – Ulcers may develop on the tongue, palate, lips, and nose.
  • Lethargy – Fvrcp often causes tiredness and fatigue as the cat’s immune system fights the infection.
  • Loss of appetite – Cats typically experience a diminished appetite.
  • Fever – Mild to moderate fevers frequently occur.

In severe cases, cats may develop pneumonia, struggle with breathing, and have more systemic symptoms. Kittens tend to develop more severe symptoms than adult cats. Without treatment, Fvrcp symptoms may persist for 2-4 weeks before improving.

Diagnosing Fvrcp

Fvrcp is diagnosed through a combination of a physical exam, medical history, and lab tests. The veterinarian will look for common symptoms of Fvrcp during the physical exam, such as sneezing, eye and nasal discharge, lethargy, and loss of appetite. They will also ask about the cat’s potential exposure history to Fvrcp. In particular, they will inquire if the cat has had contact with other infected cats.

Some of the key diagnostic tests for Fvrcp include:

  • Polymerase Chain Reaction (PCR) test – This detects viral DNA associated with Fvrcp, such as feline herpesvirus, in samples from the cat’s nasal discharge or conjunctiva (inner eyelid). A positive PCR test confirms Fvrcp infection (1).
  • Virus isolation – Samples are taken from the cat and exposed to cell cultures. Presence of cytopathic effect indicates active viral infection.
  • Serology testing – Looks for antibodies to Fvrcp viruses. A 4-fold rise in antibody levels between acute and convalescent serum samples helps confirm recent/current Fvrcp infection.

In mild cases, a presumptive Fvrcp diagnosis can be made based on clinical signs and exposure history alone. However, lab tests are recommended to confirm the diagnosis whenever possible. They also allow identification of the specific virus involved.

Treating Fvrcp

There is no cure for Fvrcp, so treatment focuses on managing symptoms and preventing complications. Supportive care is a crucial part of treatment and may include:

  • Intravenous fluids to prevent dehydration from excess nasal or eye discharge [1]
  • Appetite stimulants if the cat is not eating
  • Nebulization to help clear nasal discharge and promote breathing
  • Saline nose drops to keep nasal passages moist if congested
  • Topical eye medications for conjunctivitis
  • Antibiotics for secondary bacterial infections

Antiviral medications may be used in severe cases to inhibit viral replication. Famciclovir and feline recombinant interferon are commonly used. Cats may need to take antiviral medication lifelong if they have frequent flare-ups.[2]

Supportive nutritional supplements can also help strengthen the immune system. Lysine supplements may help inhibit viral replication and reduce the frequency and severity of flare-ups.[1] Probiotics can support good gut health, which promotes overall immune function.

The main goals of treatment are to manage clinical signs, prevent secondary infections, avoid dehydration, and support nutrition and immunity. With proper supportive care and monitoring for complications, most cats can live comfortably with Fvrcp.

Complications of Fvrcp

Despite being self-limiting in most cats, Fvrcp can lead to serious complications in some cases. One of the most common complications is secondary bacterial infections. Cats with Fvrcp often have inflamed nasal and ocular tissues which can become vulnerable to opportunistic bacterial infections. Common secondary invaders include Streptococcus, Staphylococcus, and Bordetella species. These bacteria can cause pneumonia, conjunctivitis, rhinitis, tracheobronchitis, and sinusitis (1).

Another potential complication is persistence of the virus in a latent state. Like other herpesviruses, feline herpesvirus-1 can remain dormant in nerve ganglia and reactivate later in life during periods of stress or immunosuppression. Latent infections are especially common with the ocular form, leading to recurring conjunctivitis. Chronic nasal discharge is also possible if the virus persists in a cat’s nasal passages (2).

Rarer complications include corneal ulcers, eosinophilic keratitis, abortion, fading kitten syndrome in newborn kittens, and upper respiratory obstruction requiring emergency treatment (3). While most cats recover fully, Fvrcp can occasionally be fatal if secondary infections are severe or affect vital organs.




Prognosis for Fvrcp

The prognosis for cats with Fvrcp depends on the strain of the virus and severity of symptoms. With supportive care from a veterinarian, most cats recover fully from acute symptoms within 1-2 weeks ( However, Fvrcp can cause lifelong latent infections. After initial recovery, cats can experience flare ups of respiratory symptoms throughout their lives, especially during times of stress. These recurrent infections tend to be milder than the initial bout. With prompt veterinary treatment during flare ups, most cats will recover quickly.

For kittens, the prognosis is more guarded. Kittens with Fvrcp can develop severe upper respiratory infections leading to pneumonia. Sadly, the mortality rate in untreated kittens can exceed 50% ( However, with intensive veterinary care, most kittens will recover fully.

Overall, the long term prognosis for Fvrcp is good, especially if the initial infection is managed by a veterinarian. Most cats go on to live normal lives despite chronic latent infections. However, lifelong veterinary care is recommended to monitor recurrences and treat flare ups. With prompt treatment, cats can manage recurrent Fvrcp infections and enjoy good quality of life.

Preventing Fvrcp

There are a few key ways to help prevent FVRC in cats:

Vaccination is very important. Kittens should receive a series of vaccines for FVRC starting as early as 6-8 weeks old. Adult cats need regular booster vaccines to maintain immunity. Core FVRC vaccines protect against rhinotracheitis, calicivirus, and panleukopenia viruses. Vaccines won’t completely prevent infection, but will reduce severity of symptoms if a cat is exposed. [1]

Practice good biosecurity measures. Isolate any new cats before introducing them to your household. Have dedicated food bowls, litter boxes, and toys for each cat. Clean and disinfect surfaces regularly. Avoid contact with stray cats or bringing infected cats into your home. [2]

Reduce stress for your cat. Stress can weaken the immune system and reactivate latent FVRC infections. Keep litter boxes clean and reduce household changes. Diffusers, routine, and playtime can help reduce stress. Monitor cats closely when changes occur.

With vaccination and biosecurity, FVRC can be well controlled. But it’s highly contagious, so vigilant prevention is key.

Living with a Cat with Fvrcp

Cats that have been diagnosed with Fvrcp require special care and attention at home to manage their symptoms and prevent transmission to other cats. Here are some tips for caring for a cat with Fvrcp:

Isolate the infected cat in a separate room if you have other cats in your home. Fvrcp is highly contagious and can spread through sneezing, eye and nasal discharge. Separate food bowls, litter boxes and bedding should be used for the infected cat (Source).

Clean the sick cat’s eyes and nose daily with warm water and cotton balls to remove discharge and prevent irritation. An antibiotic eye ointment may be prescribed by your vet (Source).

Use a cool mist humidifier and saline nose drops to help loosen nasal secretions and make breathing easier for your cat (Source).

Feed soft, appetizing foods that are easy to eat if your cat has mouth ulcers from Fvrcp. Ensure your cat stays hydrated by adding water to food or syringe feeding water.

Monitor your cat closely and return to the vet if symptoms worsen or do not improve with treatment. Fvrcp requires ongoing management and cats may have flare ups throughout their life.

Zoonotic Potential

Unlike many other cat diseases, feline viral rhinotracheitis Fvrcp does not directly pose a zoonotic risk for humans. This means that humans cannot catch Fvrcp directly from infected cats. Fvrcp is caused by feline herpesvirus type-1 (FHV-1), which is a species-specific virus that only infects cats [1].

However, humans with compromised immune systems should take precautions around cats with Fvrcp, as they are more susceptible to opportunistic infections from bacteria and fungi that may take hold during an Fvrcp infection[2]. Proper hygiene such as hand washing is recommended when handling a cat with active Fvrcp symptoms.

While Fvrcp itself does not pose a risk for human infection, prolonged or recurrent Fvrcp infections in cats can cause chronic eye and respiratory inflammation. This inflammation allows secondary invaders like bacteria and fungi to take hold and potentially spread. So Fvrcp creates an opportunistic pathway for zoonotic disease, rather than being zoonotic itself.


In summary, FVRCP stands for feline viral rhinotracheitis, calicivirus, and panleukopenia. It is a common combination vaccine given to cats to help protect them against these three highly contagious and potentially serious feline diseases. While the FVRCP vaccine is considered very safe, like any medication, there is a small risk of side effects or adverse reactions.

The most common side effects are mild and temporary, like fever, lethargy, and soreness at the injection site. More severe reactions are possible but very rare, like facial swelling, hives, or anaphylaxis. Overall, the risks associated with the FVRCP vaccine are far outweighed by the protection it provides against deadly contagious diseases in cats.

While the FVRCP vaccine cannot make a cat “sick” in the conventional sense, some short-term side effects are possible. However, these are mild and transient. The vaccine ultimately works to prevent illness in cats by stimulating immunity against the highly contagious viruses that cause feline upper respiratory infections and panleukopenia.

In conclusion, the FVRCP vaccine provides important protection that greatly improves a cat’s quality of life and lifespan by preventing dangerous infectious diseases. While mild and temporary side effects are possible, they are far less risky than the illnesses the vaccine prevents. Overall, the FVRCP vaccine is considered very safe and highly effective for cats.

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