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FIP Symptoms: Signs of Infected Cats

Symptoms of FIP

The feline coronavirus (FCoV) can cause the life-threatening disease Feline Infectious Peritonitis, or FIP. Cats that contract the mutated version of this virus can develop severe symptoms associated with it, so it’s very important to detect and diagnose FIP early.

In this article we’ll cover the various signs and symptoms of FIP in cats, as well as diagnosis techniques. By understanding what to look for if your cat is ill, you will be better prepared to seek out medical advice quickly and potentially save your beloved pet’s life.

Importance of Early Detection of FIP

Early detection of FIP is vital in order to start appropriate treatment and prevent further complications.

Rule out other diseases

When it comes to diagnosing Feline Infectious Peritonitis (FIP), ruling out other diseases is an essential part of the process. It is possible for a cat to experience similar symptoms as those of FIP, but be suffering from something else entirely.

Therefore, differentiating between FIP and these other conditions can be crucial in providing treatment options that are appropriate, effective and safe. The failure to rule out a range of common feline illnesses such as conjunctivitis or urinary tract infections could mean the wrong diagnosis and incorrect treatment plan being pursued which may lead to serious consequences for your pet’s health.

Diagnosing FIP is complex; there are several tests your vet needs to undertake before they can confirm their suspicions such as antibody tests and blood work-ups, all helping towards ruling out any underlying condition or illness.

Begin treatment early

It is critically important to begin treatment for FIP as soon as possible. Since this disease can progress quickly and become fatal without therapy, early detection and prompt medical intervention is key in improving outcomes.

Cats with FIP often show non-specific symptoms such as lethargy, fever, anorexia or weight loss, which can sometimes make it difficult to diagnose the disease. Additionally, there are currently no effective therapies for treating feline infectious peritonitis (FIP).

Timely intervention also helps prevent a decrease in quality of life due to organ failure associated with advanced stages of FIP.

Early Signs 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 prescribed medication like antibiotics early on.

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 feline infectious peritonitis (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.

Advanced Signs 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 feline infectious peritonitis (FIP). FIP is an inflammatory disease that 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.

Commonly seen symptoms include fever, weight loss, vomiting or diarrhea, lethargy and poor appetite.

Since organs work together to create a functioning system within our bodies any infection or disorder affecting these organs has the potential to be life threatening when not properly treated and monitored by veterinary professionals.

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.

Therefore making early diagnosis essential for potentially succeeding with treatment plans succecssfully. Early detection might include understanding non-specific symptoms such as behavioral changes , fluctuating fevers , familiarize yourself with common signs of FIP helping veterinarian professionals sooner rather than later diagnose this condition before permanent organ damage occurs .

Persistent high 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 but if the evidenced by elevated white blood cell counts in laboratory tests then it needs immediate attention from a veterinarian since this condition can quickly become life-threatening to cats if left untreated.

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.

Along with visual identifiers like bulging or tender belly associated with abdominal swelling; you should also watch out for more general symptoms such as persistent fever that can reach 40° C, lethargy that doesn’t improve when resting and low appetite that leads to loss weight in cats infected with FIP virus.

Eye problems

Eye problems are a common indicator of Feline Infectious Peritonitis (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.

Cranial nerve deficits such as head tilt, facial paralysis leading to squinting or drooping eyelid(s), imbalance while walking is also commonly seen in cats suffering from neurological symptoms due to FIP.

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.

Clinical Signs of Non-effusive Dry FIP

Typical symptoms of this form of FIP include lethargy, fever, anorexia, weight loss and jaundice.


Lethargy is commonly reported as one of the clinical signs associated with Feline Infectious Peritonitis. It can appear in cats either non-effusively, effusively or ocularly and can be a sign that something more serious is occurring.

Many cats exhibit this symptom of apathy before any other symptoms arise, indicating why it’s important to observe for lethargy as soon as possible before other advanced stages develop.

The early signs and symptoms of feline infectious peritonitis are often generalised yet easily recognised. One particular symptom that occurs in most cases would be excessive tiredness or listlessness, which may involve staying still for long periods or prolonged sleeping behaviour outside regular habits.

This lack of energy in the cat’s activities may eventually lead to weight loss despite having an increased appetite due to its weakened state – this will further limit their activity levels leading to greater fatigue over time.

It’s because of these broader effects on the body that early detection is essential when diagnosing FIP : To rule out any other illnesses and provide appropriate treatment sooner rather than later which greatly improves prognosis chances considerably.

Another common indicator for FIP would be behavioural changes: Changes from being social around people into becoming anti-social by avoiding people completely (even if they have been previously friendly).


Fever is a common clinical sign associated with FIP, however it is non-specific and can be present in cats suffering from various illnesses. It’s important to remember that fever may be the only clinical sign exhibited by cats with non-effusive dry FIP, making it an important symptom for veterinarians to consider when evaluating cats for this disease.

Once a cat develops a fever caused by FIP, the disease rapidly progresses and is nearly always fatal. Diagnosing FIP can also be challenging due to its vague symptoms, as many other diseases have similar manifestations including respiratory infections and inflammatory disorders.

Therefore it’s essential that persistent or fluctuating fever coupled with one or more of the classic physical signs of FIP such as weight loss, ocular discoloration or neurological abnormalities should prompt investigation into possible feline infectious peritonitis infection in order to begin timely treatment and supportive care where appropriate.


Anorexia is commonly recognized as one of the nonspecific and non-localizing signs of FIP observed in cats. Anorexia refers to a lack or loss of appetite which can result from decreased drive to eat due to pain, disease, or injury.

Cats with FIP suffer from poor appetite and develop anemia due to resulting nutrient deficiencies that affect their overall health and hinder normal functioning. Symptoms such as listlessness, lethargy, weight loss, and fever are often accompanied by anorexia in cats experiencing life-threatening virus like FIP.

It’s important for cat owners to recognize these symptoms early on so that they may seek veterinary assistance before it’s too late. Whether caused by viral infection or other diseases related issues ultimately need specific testing for accurate diagnosis; Veterinarians use physical examination along with blood tests & antibody tests to diagnose FIP accurately.

Weight Loss

Weight loss is a common clinical sign of FIP, especially in cases involving dry FIP. Symptoms associated with weight loss can vary, depending on the severity of the disease. Early signs may involve decreased food intake and slower than normal growth rate, while more advanced stages could include significant decrease in body mass over a short amount of time as well as reduced energy levels and muscle wasting.

Cats that are suffering from dry FIP may display additional symptoms along with weight loss, such as behavioral changes, fluctuating fever and anorexia.

The presence of unexplained or rapid weight loss should not be ignored when it comes to cats showing signs consistent with feline infectious peritonitis (FIP). If your cat appears thinner than usual without explanation or seems to be losing an excessive amount of fur for no discernible reason, then it’s important you seek professional veterinary assistance immediately.


Jaundice is a sign observed in cats with FIP, typically alongside other signs of hepatic failure or hepatomegaly (enlarged liver) such as lethargy and weight loss. Upon physical examination, the cat’s skin may be yellowish in color which may especially be visible on its belly and eyes.

In some cases, jaundice can cover all of the cat’s body. Jaundice results from an increase in bilirubin levels – pigmented molecules released into circulation by red blood cells that have broken down – leading to subsequent accumulation.

It indicates a disruption somewhere within the biliary tree which includes the gallbladder and connected structures between the liver and small intestines necessary for digestion. Detection of this clinical sign is critical for diagnosis since FIP has no definitive lab tests; jaundice often helps veterinarians identify underlying issues such as liver related diseases like feline infectious peritonitis or neoplastic changes associated with chronic cholangitis or malignant tumors involving these organs.

In cats suspected with FIP, their total bilirubin counts need to be evaluated during laboratory testing along with complete blood cell count whereas specialized tests such as biochemical profiles are also essential for conclusive diagnosis before commencing treatment plan.

Clinical Signs of Effusive Wet FIP

Thoracic, abdominal and scrotal swelling are some of the signs associated with effusive wet FIP.

Thoracic Swelling

Thoracic swelling is a clinical sign associated with effusive wet FIP, where fluid accumulation occurs in the chest. This can lead to difficulty breathing and affect normal functioning of organs such as heart rate, temperature regulation and gas exchange.

Thoracic swelling indicates advanced stages of FIP and commonly presents itself through an increase in respiration rate or gurgling noises when the cat breathes. If thoracic swelling is present for long periods of time it may lead to increased pressure being placed on internal organs causing them to become malnourished due to decreased blood flow and oxygen supply.

Additionally, if untreated persistent thoracic swelling may cause permanent damage to vital organs, ultimately leading towards death if left unchecked for a prolonged period of time.

Abdominal Swelling

Abdominal swelling is a clinical sign associated with the Feline Infectious Peritonitis (FIP) Effusive form. This form of FIP is characterized by the development of fluid in the chest or abdomen, also known as abdominal effusion.

The gastrointestinal system and its organs get surrounded by this extra, abnormal fluid. Radiography, ultrasonography and abdominocentesis are diagnostic procedures used to ascertain whether abdominal effusion has occurred in cats with suspected FIP.

In addition, fluid analysis can provide highly indicative results to diagnose abdominal effusion caused by FIP accurately.

In some cases of FIP, damage to blood vessels can occur causing inflammation that leads to increased levels of fluids leaking into cavities such as chests or bellies leading to most commonly observed sign – abdominal swelling.

Scrotal Swelling

Scrotal swelling is a common symptom of effusive wet FIP, a type of feline infectious peritonitis (FIP) which is characterized by the development of body cavity effusions. Scrotal swelling in cats can be identified by pet owners when there is an unexplained change in scrotal size, particularly if it occurs quickly or comes with other signs such as lethargy and fever.

This form of FIP most commonly affects young cats and has a rapid onset with symptoms such as abdominal fluid accumulation, thoracic enlargement, weight loss, jaundice, and persistent high fever.

With scrotal swelling being among the main clinical symptoms that veterinarians use to identify this condition early on – usually before other signs appear – it’s important for pet owners to be aware of them so they can seek help immediately for their cat should any changes arise.

Clinical Signs of Ocular FIP

Keep an eye out for signs of FIP such as discoloration of the iris, loss of vision, corneal thickening and hypopyon.

Iris Discoloration

Iris discoloration is a clinical sign that can be seen as indicative of ocular form of FIP. It typically manifests as change in the color of iris, abnormal eye cloudiness or flocculant appearance (white-specks) inside the pupil area due to inflammation from an infection caused by the virus that leads to FIP.

Corneal thickening and hypopyon may also accompany this sign which usually, if left untreated, can lead to permanent vision loss eventually. Early detection and diagnosis of this condition is important in order to start prompt treatment with antiprotozoal agents like cloranfenicol and thiamphenicol to reduce further risks associated with it.

It should be noted that while iris discoloration may indicate FIP presence when it appears alone or paired with pyogranulomatous anterior uveitis, other fungal infections too have been known in rare cases where ocular signs similar those found in FIP present themselves; therefore, proper diagnostic testing such as blood tests and antibody tests should always be done by a veterinarian prior making a conclusive diagnosis for any potentially dangerous conditions related to eyes or visual abilities.

Loss of Vision

Loss of vision is one of the most noticeable signs that your cat may have ocular FIP. It’s an advanced symptom and can indicate a more serious form of the virus has already been active in your pet.

Other common symptoms related to eye-related manifestations associated with FIP include discoloration of the iris, thickening of the cornea, presence of hypopyon (a pus-filled pocket at the back side of the anterior part), or even detachment from retina due to inflammation inside the eye structure.

Pyogranulomatous anterior uveitis (inflammation) is one such manifestation which lays out signs like Handlight Sign (yellowish dispersal when eyes are exposed to a focused beam light like a torchlight).

This syndrome is related to significant reduction in eyesight along with insufficient inflow/outflow cystic structures and lesions in iris causing destruction inside orbital cavity too if it’s left untreated over time.

Corneal Thickening

Corneal thickening is an important clinical sign associated with FIP. This condition occurs when the outer portion of the eye, known as the cornea, becomes thicker than normal due to inflammation.

In cats, this can be caused by either a virus or bacteria and it can take weeks before its effects become noticeable. Usually, what makes this symptom easier to identify is if other signs such as cloudiness in vision or pain are present at the same time.

A cat experiencing corneal thickening may display difficulty seeing clearly and possibly experience some discomfort or pain because of their decreased vision quality. If left untreated, this condition could lead to further complications such as permanent damage to both eyes from irregular pressure on them from one another.


Hypopyon is a medical term used to describe an accumulation of white blood cells at the base of the cornea, which often appears when inflammation or infection affects the eye. It is most commonly associated with uveitis, an inflammation inside the eye that occurs as a result of FIP in cats.

Uveitis can cause a cat’s pupils to become enlarged and thickened; therefore, when looking at these signs alone it can be difficult to diagnose FIP – but hypopyon offers solid insight into whether or not a diagnosis may be accurate.

Hypopyon is caused by leukocytes (white blood cells) entering through the iris and accumulating within the interior chamber of the eye. This, then leads to direct observations from physical examination like visible cloudiness in one or more parts of their eyeball or pupillary changes during light exposure tests performed by veterinarians.

Retinal detachment

is a condition that occurs when the retina pulls away from the underlying supportive tissue and blood supply. It can be caused by a number of medical conditions, such as high blood pressure, an overactive thyroid gland, or kidney disease.

In cats with Feline Infectious Peritonitis (FIP), granulomatous changes in addition to retinal hemorrhage and detachment may occur.

Clinical Signs of Neurological FIP

Look out for signs such as imbalance, head tilt, seizures and behavioral change. Continue reading to learn about the diagnosis of FIP.


Imbalance is a common symptom of Feline Infectious Peritonitis (FIP), and is often the first indication that something is wrong. In cats with FIP, imbalance can manifest as difficulty walking or loss of coordination–depending on the severity of the condition.

If switching from lying to standing position, some cats may sway back and forth due to an inability to quickly regain their balance. The cause for this particular symptom can vary depending on which type of FIP your cat has developed; it could be due to neurological damage or fluid accumulation in the abdomen or thoracic cavity.

Imbalance in cats should not be taken lightly and should be brought up with your vet, as early diagnosis improves prognosis significantly when it comes to treating this condition. Your veterinarian will start by performing physical examinations such as looking at motor function and reflexes in order for them to evaluate if a cat’s walk appears coordinated.

Head tilt

Head tilt is an important clinical sign of neurological FIP as it is often indicative of vestibular syndrome. Vestibular syndrome occurs when the part of the brain responsible for balance doesn’t function correctly, causing imbalance and difficulty with coordination.

In cats, this manifests itself as a pronounced head tilt to one side or another. This can be accompanied by eyes that don’t seem to move together normally – one may dart back and forth quickly while the other remains still – as well as rolling movements caused by gravity that make it difficult for the cat to remain upright.


Seizures may be a clinical sign of feline infectious peritonitis (FIP) when neurological involvement is present. The neurological form of FIP manifests in cats as ataxia, nystagmus, and even seizures.

Some telltale signs that your cat may be experiencing a seizure due to FIP include inappropriate elimination, dementia-like behaviors such as circling or aggressiveness, decreased coordination and balance, and strange vocalizations or loss of consciousness.

Any time your cat experiences a seizure you should take them to the veterinarian promptly for further evaluation and diagnosis.

Seizure activity can quickly cause permanent damage if left untreated so recognizing the indications early on is essential for maintaining the best possible health of an infected animal.

Behavior change

Changes in behavior can be an early indicator of Feline InfectiousPeritonitis (FIP). Certain behaviors may indicate neurological forms of FIP, such as ataxia, nystagmus, seizures, incoordination and intention tremors.

Other non-neurological signs of FIP include weight loss, weakness or lethargy. One common symptom that is worrying owners is sudden changes in their cat’s behavioral pattern. Cats might hide away more often than usual or show aggression when they normally wouldn’t; this could indicate some kind of underlying medical condition.

Diagnosis of FIP

Veterinarians can begin by conducting a physical exam and running diagnostic tests such as blood work or antibody tests.

Physical examination and imaging results by a veterinarian

A physical examination conducted by a veterinarian is an essential component in the diagnosis of FIP. Through a physical exam, veterinarians have the opportunity to assess an animal’s external appearance and internal health condition.

By noting any irregularities visible from physical inspection, such as scrotal swelling or thoracic enlargement indicating the presence of fluid-filled organs, vets are able to detect any potential signs of FIP.

The effusive form of FIP can be identified through these clinical examinations; if there is evidence that fluids have built up within certain organs (thorax, abdomen & scrotum), this could suggest effusion on the side affected with FIP which can help confirm suspicion for diagnosis.

Physical circumcision performed by experienced veterinarians also contributes towards confirming whether respiratory signs are related to pneumonia/bronchial irritation rather than being induced through FIP itself – another relevant process exclusively assessed through veterinary consultation.

Blood tests

In the case of FIP, a blood test can help rule out other diseases and provide further clues towards diagnosing this condition.

There are many readings like blood cells, proteins as well as liver results that can be provide multi-layer diagnostics. Each reading narrows down the answer further and makes it more certain to identify FIP.

Furthermore, tests conducted during a physical examination may identify other underlying causes for symptoms that are not directly linked to FIP itself but support its diagnosis indirectly; identification of significant changes in acid base balance or protein levels may indicate inflammation caused by infection and increase likelihood for diagnosing feline infectious peritonitis.


Antibody tests

Antibody tests are commonly used as a diagnostic tool for determining the potential presence of infectious agents. In terms of Feline Infectious Peritonitis (FIP), antibody tests can be used to measure feline coronavirus antibody levels, however, false negative results have been known to occur in cats with anti-FCoV antibodies present their serum or effusion.

Antibody tests alone cannot diagnose FIP and additional clinical signs consistent with FIP need to be present alongside positive test results for an accurate diagnosis. There is currently no definitive test available for diagnosing FIP, making it important that other diseases which may cause similar symptoms in cats – such as ringworm or cancer – are ruled out through careful physical examination, further testing and medical history evaluation by a veterinarian before advancing any conclusions or strategy regarding treatment.


The early detection of Feline Infectious Peritonitis (FIP) is essential, as there are limited treatment options available and the prognosis for cats with FIP is generally poor. Symptoms can be vague initially, including a rising and falling fever, loss of appetite, and energy loss; therefore close observation by an owner or veterinarian to detect any changes in behaviour is crucial.

Once more advanced signs become apparent such as organ failure, persistent high fever, fluid accumulation or eye problems then diagnosis may require physical examination by a vet along with blood tests and antibody tests.

Early detection will enable prompt recognition of proposed treatments when available making it important to be aware of all possible symptoms associated with FIP.


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