There are four distinct stages of FIP involved in an infection with this virus: initial exposure and incubation, primary viremia, secondary viremia, and clinical FIP.

 

Stage of FIP: Initial Exposure and Incubation

The Feline coronavirus (FCoV) is present in many environments, so cats are very likely to be exposed at some point during their life. This initial infection is usually benign, but unfortunately there is a risk of the virus mutating and causing FIP in some cats.

The incubation period for this mutation can range from a few weeks up to several years, but cats are most at risk of developing clinical FIP within the first 6 weeks after they’ve been initially infected with the virus.

Experiments have concluded that as little as six weeks can be enough time for an infected cat to develop into full-blown illness.

During initial exposure and incubation periods, it’s important to note that infected cats shed an unusually large volume of virus particles which can quickly lead to other household pets coming down with the infection too.

 

Stage of FIP: Primary Viremia

Primary viremia is the stage during an infection of Feline Infectious Peritonitis (FIP) virus, where cats’ immune system starts to respond to the foreign invader. During this stage, high levels of FCoV can be found in their blood.

This marks the start of a battle between the cat’s body and virus, and also marks when mutations become more likely to occur due to decreased resistance.

Cats with primary viremia display a heightened response from their immune systems trying hard to protect them from any harm caused by the pathogen entering its body.

Some cats will be able to rid their bodies of the virus with a strong immune response.

 

Stage of FIP: Secondary Viremia

Secondary viremia refers to a subsequent stage that affects the cats that were not able to fight off the virus during the primary stage.

In this stage, the bone marrow and other tissues have been invaded by the virus. The virus can then remain in a passive state in the bone marrow for quite some time.

But besides that, FIPV levels in the blood start to increase and eventually reach a point where cats are no longer able to keep it under control. Unfortunately, by this time many systemic inflammatory processes have already set in as FIPV has taken hold of vital organs and tissues.

As its name suggests, during secondary viremia the virus is starting to spread throughout other organs leading to more severe signs that can quickly become life-threatening if not addressed promptly.

The severity of the primary immune response or how well a cat’s body is capable of controlling the infection plays an important role in determining at what level will the virus start spreading beyond just one organ system.

During this crucial period, cats may experience persistent fever (over 103°F) decreased appetite and general worsening condition due their failing immune system which is trying extremely hard to control the mutated viruses but cannot so they must rely on treatment plans with antivirals among other medications.

 

Stage of FIP: Clinical FIP

At the clinical stage of FIP, cats are beyond being able to contain the virus. This is partly due to an alteration in one of the proteins found in some types of FCoV called FIPV. FIPV causes vasculitis, which is inflammation and swelling around a group of cells or organs.

An accumulation of fluid within body cavities, leading to fluid build-up and excess pressure on vital organs, can also occur at this stage. Cats with FIP may exhibit symptoms such as weight loss, fever, dehydration swollen abdomen or head area and breathing difficulties due to chest congestion.

Destruction from infections inside vital organs will begin at this point, potentially leading to system organ failure. This usually manifests later as kidney disease or neurological damage caused by inflammation in their brain tissue.

 

Stage of FIP: Organ Damage

This is the last stage of FIP where the inflammation is already causing damage to organs and the cat exhibit other subsequent problems.

Some of the organs commonly affected include:

Abdominal organs: FIP often results in the formation of granulomas (small nodules of inflammatory tissue) in the abdominal organs, such as the liver, spleen, and kidneys. This can lead to dysfunction and failure of these organs.

Kidneys: The kidneys may be affected by granulomatous lesions, leading to renal failure.

Central Nervous System (CNS): FIP can cause neurological symptoms when it affects the CNS. Cats with neurological FIP may exhibit behavior changes, seizures, and difficulty walking.

Eyes: Ocular (eye) involvement is common in FIP, leading to inflammation, cloudiness, and sometimes blindness. This is known as ocular or dry FIP.

Cardiovascular system: In some cases, FIP may affect the heart and blood vessels, leading to cardiovascular issues.

These continuous deterioration in the cat eventually will lead to paralysis, and finally death.

 

 

Symptoms based on Stages of FIP

Sign during Early Stages of FIP 

Cats may present with early non-specific symptoms, such as behavioral changes, weight loss and loss of appetite, as well as fluctuating fever.

 

Non-specific symptoms

FIP has a wide range of non-specific symptoms which can easily be mistaken for other illnesses. These initial signs are usually vague and include listlessness, lethargy, decreased appetite, weight loss, and fluctuating fever.

In some cases, cats will display behavioral changes accompanying these physical symptoms.

It’s essential to pay attention to tiny shifts in your cat’s health regime such as increased or decreased energy levels as this may be the first sign of FIP. Despite being so common in cats the subtle cause makes it difficult to detect at initial stages unless you attend closely for additional signs like Anorexia or Pica (a condition where they eat things that they shouldn’t) which are frequently seen during FIP infection.

Fluctuating fevers could also mean that there is something wrong with your cat so please look out for any major temperature changes when checking on them periodically throughout the day such as documented fever lasting over 24 hrs despite treatments given by a vet.

 

Diarrhea

When Feline Coronavirus (FCoV) first gets into a cat, it infects the small intestine, sometimes causing diarrhoea. The virus is shed in the faeces from as early as two days after infection and then for a few weeks to months. From the intestine, the virus goes into the bloodstream, resulting in FIP in some unlucky cats, but most cats mount a successful immune response and get rid of the virus—going on to lead perfectly healthy and normal lives.

Initial infection with FCoV at any age, not just in kittens can cause diarrhoea and the severity can range from mild, through chronic, to severe and life-threatening. The virus initially damages the lining of the small intestine. Unfortunately, in some cats, FCoV can damage the small intestine quite severely, leading to a permanent tendency to vomiting or diarrhoea and what is known as “malabsorption syndrome,” where the affected cat is unable to benefit from the nutrients he or she has eaten, so fails to gain weight adequately and thrive.

 

Behavioral changes

In cats infected with FIP, owners may first notice less obvious symptoms such as decreased activity, listlessness and lack of appetite. Your cat may become far less interactive than it was before, preferring to stay in solitary locations or sleep all day.

They might also start avoiding interactions with other pets or humans. Pica is another behavioral change associated with the virus – when your pet starts eating non-food items this could be a sign they have FIP.

In addition to anorexia (total loss of appetite) you may observe your cat struggling to self-feed or show disinterest towards food entirely upon offering it – both can be indicators something isn’t right.

 

Weight loss and loss of appetite

Weight loss and loss of appetite are two of the earliest signs of FIP. When cats first become infected, they may show no symptoms until weeks or months later. However, slow weight loss and a diminished appetite can be an indication that something is wrong.

Weight loss in cats is usually subtle but should not go unnoticed by their owners – a sudden 15-20% decrease in weight over just a few days could signify the presence of FIP. Similarly, a decreased appetite even when presented with favorable food could indicate the onset of illness.

This type of symptom complex can point to organ failure caused by FIP or other serious conditions such as chronic kidney disease which left untreated can progress quickly and become life threatening for cats if not detected early on.

Many cat owners have reported observing dramatic shifts in energy levels and activity associated with these symptoms which further emphasize their importance in diagnosis and treatment decisions made by veterinarians and pet owners alike.

 

Fluctuating fever

Fluctuating fever in cats is typically defined as alternating episodes of high and low temperatures. It’s one of the earliest clinical signs associated with FIP.

This kind of fever can vary daily, oscillating between normal body temperature and dangerously high temperatures. As this can happen suddenly, it’s important for cat owners to monitor their pet’s temperate regularly as any sudden changes could be a sign of FIP or another serious health concern.

It’s easy to confuse a fluctuating fever with persistent high fevers that cats may have when sick but the two are vastly different illnesses requiring distinct forms of treatment.

 

Signs during Advanced Stages of FIP

 

Symptoms may progress to more severe effects, such as organ failure and fluid accumulation. Keep reading to find out more!

Organ failure

Organ failure is one of the most serious consequences associated with FIP. This can affect various organs, such as the kidneys, liver and many others.

When it reaches its most advanced stage, organ dysfunction or failure may result. This organ damage can cause a wide variety of symptoms which vary depending on the specific locations impacted in the body.

If left untreated for too long it adds immense strain on the affected animal’s overall physical health until eventually turning into catastrophic illness or resulting in death if not caught early enough and treated accordingly.

 

Persistent high fever

Unceasing Fever is a common clinical sign associated with advanced stages of Feline Infectious Peritonitis (FIP). This fever can reach temperatures between 102 °F to 105°F and last for weeks or months.

It is important to make an early diagnosis as it helps in ruling out other diseases and initiating treatment. The fever is caused by inflammation resulting from widespread infection, which may be accompanied by signs such as lethargy, abdominal swelling, loss of appetite, weight loss and jaundice.

If the fever persists despite antibiotic therapy or anti-inflammatory medication, it could be indicative of FIP. The high temperature often normalizes once proper treatment begins.

 

Fluid accumulation

Fluid accumulation is a key sign of FIP in cats and can occur in various areas of the body. In the chest, fluid builds up around the heart and lungs, leading to restricted movement and difficulty breathing.

Additionally, lymph nodes may become swollen due to blockage caused by an excessive formation of protein-rich fluid cells called pleural effusions. Fluid can also accumulate in other organs such as the abdomen or scrotum causing these areas to swell and be painful for your cat.

Furthermore, your cat’s eyes may exhibit signs from this build-up inside them including changes in coloration or opacity, corneal thickening (corneal edema) hypopyon (a white foam at back portion of eye) or retinal detachment due to intraocular pressure increase caused by FIP infection.

 

Eye problems

Eye problems are a common indicator of FIP. Ocular lesions characterized by Pyogranulomatous Anterior Uveitis can occur in cats with FIP. Symptoms may include inflammation of the eyeball, squinting, swollen third eyelids, and enlarged eyes that can impair vision or even lead to blindness if left untreated.

Animals experiencing this type of ocular manifestation may express increased tear production as well as bleeding from the eye due to ulceration caused by the infection.

Additionally, neurological symptoms related to FIP can affect the nervous system—including vision and eye problems such as contracted pupils that do not respond appropriately to light changes.

Finally, intraocular pressure elevation accompanied with corneal thickening has been seen in some cases of wet form effusive FIP which leads to potential loss of vision over time if not treated properly or promptly enough.