Calicivirus Infection and Mouth Sores in Cats

What is Calicivirus Infection and Mouth Sores in Cats?

Calicivirus infection in cats is a highly contagious viral disease that primarily affectsthe upper respiratory tract and sometimes the joints, causing sores in the oral mucosa. The causative agent, Feline Calicivirus (FCV), is an RNA virus belonging to the Picornaviridae family and is one of the most common respiratory pathogens in cats. The most characteristic feature of FCV is the formation of painful ulcers and aphthous ulcers inside the mouth. These sores can develop on the tongue, buccal mucosa, palate, or inner lip. The virus also causes typical upper respiratory signs such as rhinorrhea, sneezing, fever, loss of appetite, and weakness. However, compared to FHV, nasal congestion is milder, and mouth sores are much more pronounced. Oral lesions make it significantly difficult for cats to eat , resulting in rapid weight loss, dehydration, and malnutrition. Among the most dangerous aspects of FCV is its use.

While calicivirus infection can be mild in some cats, some virus variants can cause much more severe clinical conditions. Highly pathogenic variants, particularly those known as "virulent systemic calicivirus" (VS-FCV), can cause serious complications such as fever, facial and leg edema, skin lesions, jaundice, coagulation disorders, and multiple organ involvement. While rare, this variant can be fatal. One of the key characteristics of FCV is its resistance to environmental conditions; because it can remain active on surfaces for several days, the risk of transmission is quite high. Therefore, cats living in the same household, as well as communal living spaces such as shelters or pet shops, are the most at-risk areas for the rapid spread of the disease.

The virus may not clear completely after causing acute symptoms in cats; some cats become carriers and continue to shed the virus at low levels for an extended period. This can create a continuous cycle of infection in community settings. Furthermore, FCV is not limited to the upper respiratory tract and oral mucosa; it can also cause inflammation in the joints, causing lameness, reluctance to move, and pain. This clinical picture is called "limping syndrome" and is particularly common in young cats. With all these characteristics, calicivirus infection is a significant group of infections that both reduces the quality of life in cats and can be life-threatening when it progresses rapidly.

Calicivirus Infection in Cats and Types of Mouth Sores / Clinical Forms

Calicivirus infection can present in different clinical forms, and this clinical diversity stems from the high genetic variability of the virus subtypes. FCV strains can exhibit significantly different characteristics; therefore, the severity of the disease and the type of symptoms are not the same in every cat. The most common form is the classic upper respiratory tract infection . This form presents with sneezing, nasal discharge, watery eyes, and fever, while ulcers in the oral mucosa are the most prominent symptoms. The sores on the tongue are often round, pitted, and yellowish-white; these ulcers cause severe pain and a sudden loss of appetite. The cat will approach the food bowl and sniff, but will turn away without eating due to the pain; this behavior is typical of FCV.

Another clinical form is the oral-ulcerative form , a severe condition characterized by predominantly intraoral involvement. In this form, multiple sores may develop on the tongue, palate, and buccal mucosa; some cats may drool due to pain, develop pronounced bad breath, and experience difficulty swallowing. This form can be particularly severe in kittens and young cats.

Another clinical type of calicivirus infection is "limping syndrome," which involves joints . The virus causes inflammation in the joints, causing lameness, joint pain, reluctance to move, and generalized tenderness. These symptoms can sometimes occur without mouth sores or respiratory symptoms and can be seen in some kittens, especially those who have been recently vaccinated; however, they are usually transient.

The most serious clinical form is virulent systemic calicivirus (VS-FCV) . This variant produces severe systemic symptoms such as high fever, skin ulcers, facial and extremity edema, liver failure, coagulation disorders, jaundice, and multiple organ failure. Mortality is high and progression is rapid. Although VS-FCV is very rare, it can cause significant losses in shelters in outbreaks.

The final clinical type is chronic calicivirus carriage . Some cats may exhibit chronic symptoms lasting months or years after recovering from acute infection due to the inability to completely clear the virus. These cats may develop periodic mouth sores, chronic stomatitis, intermittent sneezing, bad breath, and loss of appetite. In chronic FCV, the constant battle between the immune system and the virus can create chronic inflammation in the mouth, and in some cats, it can progress to chronic gingivostomatitis syndrome, which requires lifelong treatment.

Calicivirus Infection and Causes of Mouth Sores in Cats

The primary cause of feline calicivirus infection and mouth sores in cats is Feline Calicivirus (FCV), which causes tissue damage by intense viral replication in the upper respiratory tract, particularly the oral mucosa. FCV infection is most often transmitted through direct contact; the saliva, eye and nasal discharges of infected cats, shared food and water bowls, toys, and carriers are the most important carriers of the virus. Even brief contact with the saliva or secretions of an infected cat is often sufficient for a cat to become ill. FCV is more resistant in the external environment than herpesvirus and can survive on some surfaces for up to several days, making the risk of transmission quite high.

The tissue tropism of the virus plays a decisive role in the development of oral ulcers. FCV replicates intensively, particularly in the epithelial cells of the oral mucosa; this replication causes cell damage, inflammation, and surface tissue shedding. This results in round, painful ulcers on the tongue, palate, and buccal mucosa. These ulcers significantly impede the cat's ability to eat and are the primary cause of anorexia.

Cats with weakened immune systems, especially kittens, older cats, FIV/FeLV-positive cats, and cats with chronic illnesses, are more vulnerable to FCV. In these cats, the virus progresses much more rapidly, and mouth sores can be more extensive, more painful, and last longer. Stress, malnutrition, crowded living environments like shelters, and poor hygiene are also significant factors contributing to the spread of FCV.

Another important factor contributing to calicivirus infection is viral mutation and strain diversity . Numerous variants of FCV exist, and these variants can lead to different clinical presentations. Some strains cause mild respiratory symptoms, while others produce multiple ulcers in the mouth. More aggressive variants can cause a virulent, systemic form of FCV, leading to multiorgan involvement. This genetic diversity makes it difficult to predict disease severity and causes each FCV case to present with different clinical manifestations.

Transmission from mother cats to kittens is also a significant factor. Kittens infected before or shortly after birth are prone to both mouth sores and severe respiratory distress. Because kittens' immune systems are not fully developed, the disease can worsen much more rapidly. Furthermore, some cats become carriers long after recovering from acute infection; these cats continue to shed the virus into the environment without showing any symptoms, creating a continuous cycle of infection, especially in shelters and multi-cat households.

Breeds Prone to Calicivirus Infection and Mouth Sores in Cats

The table below shows the cat breeds in which the disease is more pronounced and may progress more clinically. Format: Breed | Description | Susceptibility Level .

Race	Explanation	Level of Predisposition
Persian (Persian Cat)	Because of their anatomically narrow nasal structures and immune sensitivity, FCV-induced mouth sores and respiratory symptoms are more pronounced.	A lot
Exotic Shorthair	Mouth sores and respiratory symptoms may be more severe due to the Persian-like facial structure and stress sensitivity.	A lot
Sphynx	Its hairless structure increases sensitivity to environmental changes; FCV symptoms may be more intense when there is immune suppression.	Middle
British Shorthair	It carries a moderate risk; oral lesions may be more pronounced, especially when exposed to FCV during the puppy stage.	Middle
Scottish Fold	Due to genetic immune sensitivity, susceptibility to viral infections may increase; mouth sores may be common.	Middle
Maine Coon	Although generally more resistant, FCV mouth sores and lameness syndrome may develop in puppies and stressed individuals.	Little
Domestic Short Hair (Street Cat)	The frequency and severity of infection are evident due to unprotected living conditions, stress and high exposure to sources of contamination.	A lot

Symptoms of Calicivirus Infection and Mouth Sores in Cats

The symptoms of calicivirus infection and mouth sores in cats vary depending on the tissue affected by the virus; ulcers, particularly those in the oral mucosa, are the most defining signs of the disease. The earliest clinical signs observed in a cat infected with FCV are sneezing and nasal discharge . In the early days of the disease, the discharge is usually clear and watery, but over time, it can become mucopurulent (yellow-green, thick, and foul-smelling), often a sign of an accompanying bacterial infection. Sneezing spells can quickly intensify, and the cat may have to use its mouth to breathe, providing an important clue to the severity of the obstruction.

The most characteristic symptom of FCV is oral ulcers . These ulcers are most commonly seen on the upper surface of the tongue, but can also appear on the palate, buccal mucosa, and inside the lips. These ulcers are round, hollow, yellowish-white, and quite painful. The most obvious behavioral indicators of these ulcers include the cat going to the food bowl and sniffing it, then walking away without eating, refusing to feed, and exhibiting avoidance behavior when presented with food. Increased salivation due to intense pain in the mouth, bad breath , carrying the cat with its mouth half open , and difficulty swallowing are common symptoms.

Respiratory symptoms also accompany the condition. Cough , mild fever , loss of appetite , weakness , tearing , conjunctivitis , and occasionally eye discharge may be observed. While the intense eye damage seen in FHV is less pronounced in FCV, some strains can cause inflammation and temporary clouding of the eye surface. In some cats, the eyes remain half-closed and sensitivity to light is increased.

In more severe strains of calicivirus—especially virulent systemic variants—symptoms can be even more dramatic. These variants may include swelling of the face and legs, subcutaneous edema, rapid fever, lethargy, sudden loss of appetite, ulcers on the skin outside the mouth, jaundice, shortness of breath, and bleeding disorders. Because these variants progress rapidly, they can lead to serious complications within a few days.

Some cats develop limping syndrome (lameness) due to joint involvement from FCV. In this condition, the cat may refuse to walk, drag its legs, make noises when taking steps, or remain completely immobile. Lameness is usually temporary, but it can be painful and, when accompanied by mouth sores, can seriously compromise the cat's overall condition.

In cats with prolonged or chronic FCV infection, symptoms recur intermittently. These cats may experience periodic symptoms such as chronic stomatitis, gingivitis, bad breath, persistent drooling, frequent sneezing, and nasal discharge. In the chronic form, the inflammation inside the mouth can be so severe that chronic pain and malnutrition develop, affecting the cat's overall quality of life.

The diversity of symptoms associated with calicivirus infection is a result of genetic variations in the virus and variations in cats' immune responses. Therefore, not every case of FCV presents the same way; some cats may present with mild upper respiratory symptoms, while others may present with multiple ulcers and severe systemic symptoms.

Diagnosis of Calicivirus Infection and Mouth Sores in Cats

Diagnosis of calicivirus infection and oral ulcers is made using clinical examination findings, detailed history, laboratory tests, and, when necessary, advanced imaging methods. Round ulcers on the tongue , one of the most distinctive features of the disease, are a significant finding that strengthens the suspicion of FCV when examined by a veterinarian. Therefore, a careful oral examination is a key step in diagnosis. The typical morphology of the ulcers—round, pitted, and yellowish-white—is highly characteristic of FCV.

PCR testing is one of the most reliable methods for confirming a diagnosis. PCR testing, performed on samples obtained from nasal swabs, oropharyngeal swabs, oral swabs, or eye discharge, detects the genetic material of FCV with high sensitivity. PCR not only confirms Calicivirus but also helps distinguish the presence of other agents, such as FHV or Chlamydia felis, that may cause similar symptoms. In multi-cat environments, PCR testing is particularly essential for outbreak management.

Blood tests are used to assess the systemic effects of the disease. A complete blood count (CBC) indicates the level of the immune response , the presence of a possible bacterial infection, and the body's inflammatory burden. White blood cell counts are elevated in severe cases of FCV or may decrease in immunocompromised states. A biochemistry panel is important to assess liver and kidney function, especially in cases of virulent systemic FCV.

Sedation may be required during the oral examination to assess the degree of pain and extent of oral ulcers. A more detailed oral examination can be performed under sedation, particularly when stomatitis and gingivostomatitis are suspected. The severity of oral inflammation, the extent of ulcers, and the degree of gingival involvement are important criteria for diagnosis.

In cases of severe respiratory symptoms, a chest X-ray may be obtained to evaluate the possibility of secondary infection or pneumonia. This imaging helps identify changes in bronchial or interstitial patterns, areas of condensation, and inflammatory structures within the lungs.

In some cases, particularly in cats with chronic mouth sores , culture and antibiogram testing may be performed. This test detects bacterial pathogens accompanying the ulcers, not FCV, and is critical for proper antibiotic selection. Furthermore, this study plays a supporting role in distinguishing between bacterial or viral inflammation and the cause of the bad breath and increased drooling common in calicivirus infections.

In cats with eye symptoms, an ophthalmologic examination and fluorescein staining test may be performed. This test can evaluate corneal surface damage, ulcers, scratches, or viral keratitis associated with oral ulcers.

Correct diagnosis is the most critical step in determining the clinical form of FCV and shaping the treatment plan, as not every case of Calicivirus is equally severe and the clinical treatment approach varies depending on the form of the cat.

Treatment of Calicivirus Infection and Mouth Sores in Cats

Treatment of calicivirus infection and oral ulcers in cats is primarily based on supportive care , pain control , treatment of secondary infections , and immune strengthening , as no specific antiviral medication is available to completely eradicate the virus. The treatment protocol is tailored to the severity of the cat's clinical signs, the extent of oral ulcers, nutritional status, the degree of respiratory symptoms, and the presence of other comorbidities.

Because mouth sores are the most prominent symptom of FCV, oral pain management is the most critical aspect of treatment. Oral ulcers are extremely painful, and cats often refuse to eat. Because this condition can lead to rapid weight loss, dehydration, and metabolic imbalances, veterinarians generally provide pain control with appropriate analgesics. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used in certain cases, but due to the sensitivity of cats' liver and kidneys, careful dosing is essential. Pain management is the primary priority in treatment, as feeding disorders will persist even after mouth sores heal unless pain control is achieved.

Topical treatments can also be applied to control mouth sores. Antiseptic oral solutions, chlorhexidine-based mouthwashes, or mucosal soothing preparations recommended by your veterinarian can reduce inflammation in the mouth. However, when using these products, alcohol-free formulas that will not cause a burning sensation in the cat's mouth should be preferred. In some cases, veterinarians may recommend topical mucosal healing agents to accelerate the healing of ulcers.

Secondary bacterial infections are common in calicivirus infections. Open wounds in the mouth, in particular, become entry points for bacteria, and bacterial stomatitis can develop. In these cases, your veterinarian will prescribe broad-spectrum antibiotics; while antibiotic treatment doesn't eliminate the viral pathogen, it does significantly reduce purulent discharge, bad breath, and bacterial inflammation, speeding up the healing process.

Nutritional support is another key element of treatment. For cats unable to eat due to oral sores, strongly flavored wet food, pureed food, or high-calorie supplements should be used. In more advanced cases, if the cat is not eating at all, your veterinarian may recommend syringe feeding or a temporary feeding tube (esophagostomy tube) . This method can be lifesaving, especially in severe stomatitis or ulcerative cases. Because no treatment protocol can be successful without continued nutrition, reducing oral pain and supporting nutrition should be implemented simultaneously.

Nasal cleansing and humidification are crucial for cats with respiratory symptoms. Cleaning the corners of the nose with warm saline, using a vaporizer, and keeping the cat in a warm environment can all help soothe the airways. These practices not only help the cat breathe more easily but also make it easier to detect food odors.

In some severe cases of calicivirus infection, antiviral medications may be used as a support. Interferon preparations, in particular, help the immune system fight the virus; however, their effectiveness varies and they are not necessary in every case. The treatment protocol is always individualized based on the clinical presentation.

In cases of severe disease, serum therapy is administered. Because dehydration and electrolyte imbalances significantly slow healing, fluid support, vitamin supplements, and, if necessary, oxygen therapy may be administered in the clinical setting. In cases of joint involvement, "limping syndrome," anti-inflammatory therapy and bed rest are the primary treatment.

One of the most important elements of treatment is Stress management can exacerbate oral sores and respiratory symptoms caused by FCV, so the cat should be kept in a quiet room, sudden changes should be avoided, and a quiet environment should be provided.

Calicivirus Infection and Mouth Sores in Cats: Complications and Prognosis

Calicivirus infection and mouth sores can lead to a wide range of complications in cats; the severity of these complications varies depending on the virus strain, the cat's immune status, any comorbidities, and the rapidity of treatment during the acute phase. One of the most common complications is the development of chronic stomatitis and gingivostomatitis . This condition results from intense and persistent inflammation of the oral mucosa due to the constant conflict between the immune system and the virus. Cats experiencing chronic stomatitis may experience easy oral bleeding, pronounced gum recession, and persistent bad breath and drooling. These cats often require long-term treatment, oral hygiene practices, and, in some cases, advanced treatments, including complete tooth extraction.

The virulent systemic form (VS-FCV), seen in severe variants of calicivirus, is one of the most dangerous complications. In this form, the virus is not limited to the mouth and respiratory tract; it can affect the liver, kidneys, skin, muscles, and vascular endothelium, causing multi-organ damage. Symptoms include high fever, jaundice, subcutaneous hemorrhages, coagulation disorders, edema on the face and legs, skin ulcers, and sudden collapse. VS-FCV has a very high mortality rate and can become life-threatening within a few days if prompt intervention is not provided.

Oral ulcers can lead to complications related to malnutrition. Cats that go without food for extended periods are at increased risk of developing fatty liver disease (hepatic lipidosis) . This condition occurs more rapidly in overweight cats and requires immediate veterinary attention. Dehydration and electrolyte imbalances are also common secondary complications in cats with oral ulcers.

Some FCV infections cause joint involvement . This is characterized by a "limping syndrome," particularly seen in kittens, in which cats struggle to walk, limp, or experience pain when taking steps for several days. This complication is often temporary, but in some cats, it can lead to chronic joint tenderness.

In chronic calicivirus carriers, mucosal inflammation in the nose and mouth can develop into long-term symptoms such as chronic respiratory problems , intermittent sneezing, and persistent nasal discharge. In such cats, the anatomy of the nasal passages can deteriorate over time, leading to the development of chronic rhinitis.

The prognosis varies depending on the clinical form of the disease. Mild, classic upper respiratory tract infections resolve in most cats with appropriate care; however, in cats with prominent oral ulcers, recovery may be prolonged and nutritional support may be necessary. Diseases such as chronic stomatitis, virulent systemic FCV, and coexisting FIV/FeLV negatively impact the prognosis. With appropriate treatment and home care, many cats can maintain a good quality of life, but relapses are common.

Calicivirus Infection and Mouth Sores in Cats: Home Care and Prevention

Home care during the period of Calicivirus infection and mouth sores in cats is one of the most important factors determining the success of treatment. FCV significantly complicates a cat's daily life, particularly due to the pain it causes in the oral mucosa, loss of appetite, and increased drooling. Therefore, maintaining a healthy home environment, ensuring the cat can breathe easily, implementing a gentle feeding program to prevent irritation of the mouth sores, and minimizing stress are critical. The first step is to ensure the cat's environment is warm, calm, and free of drafts . A cat with upper respiratory symptoms is more sensitive to cold drafts; therefore, the room temperature should be maintained, and stress factors such as noise, intense activity, and contact with other animals should be minimized.

Mouth sores can make it difficult for cats to eat; this can lead to rapid weight loss and lethargy. A key component of home care is providing soft, flavorful food . Canned, pureed, or recovery food is more readily consumed by cats. Gently warming the food can enhance the aroma, stimulate the cat's sense of smell, and increase their desire to eat. If the cat refuses to eat, syringe feeding or water-based supplements can be administered under veterinary guidance; however, these procedures should be gentle and stress-free.

Because mouth sores complicate oral hygiene , oral care should be meticulously implemented at home. Alcohol-free, veterinarian-approved antiseptic mouthwashes or gels can reduce inflammation and control bacterial loads within the mouth. However, because the mouth is extremely sensitive, harsh procedures should be avoided; cleanings should be brief and gentle. Rubbing a finger or hard object inside a cat's mouth can further irritate the sores; therefore, cleaning products should be used only for limited periods and in controlled amounts.

In cases accompanied by respiratory symptoms , nasal irrigation and humidification should be performed. While calicivirus is usually associated with mouth sores, nasal discharge and congestion are also prominent in some cats. Cleaning the nasal passages with warm saline, loosening and removing dried discharge, and installing a vaporizer in the environment provide significant relief for the cat. Humid air reduces nasal congestion by loosening mucus and positively impacts the cat's eating behavior.

One of the most important components of home care is isolation and hygiene protocols. Because calicivirus can survive on surfaces for some time, avoiding shared containers, changing bedding and toys frequently, cleaning the litter box daily, and washing hands after contact significantly reduce transmission. If there are other cats in the home, the infected cat should be kept in a separate room, if possible, and should not come into contact with other cats until it has fully recovered.

A key step in prevention is a regular vaccination program . The FCV vaccine is highly effective in reducing disease severity and viral shedding. While the vaccine doesn't completely prevent infection, it significantly helps alleviate oral sores and systemic symptoms. When a new cat is brought home, a quarantine period of at least 10–14 days should be observed, and they should not be brought into the same living space with other cats until their health checks are completed.

The success of home care depends largely on stress management . Stress can both suppress the immune system and accelerate viral replication. Therefore, the cat's daily routine should be maintained, sudden environmental changes should be avoided, and loud noises and crowded environments should be limited as much as possible. Additionally, environmental enrichment elements such as hiding places, soft bedding, and window-side observation points increase the cat's psychological comfort.

Throughout the home care process, the cat's appetite, water consumption, oral pain level, amount of salivation, breathing pattern and general activity level should be observed regularly; veterinary intervention should not be delayed in case of any signs of deterioration.

Calicivirus Infection and Mouth Sores in Cats Owner Responsibilities

Caring for a cat with a calicivirus infection and mouth sores requires daily attention, patience, and discipline. The owner's primary responsibility is to closely monitor the cat's clinical signs and actively participate in the recovery process. Any changes observed during this period—decreased appetite, increased drooling, food reluctance, foul breath, nasal discharge, or rapid weight loss—may indicate disease progression and require prompt veterinary intervention.

One of the most important duties of owners is to follow the treatment protocol completely and on time . Veterinarian-prescribed antibiotics, painkillers, antiseptic oral products, eye drops, or antiviral preparations should never be interrupted, and the recommended dosage intervals should be strictly adhered to. Medications can be difficult to administer when the cat is in high pain; therefore, it is crucial for owners to learn the correct administration methods and to be able to administer them without causing stress to the cat.

Feeding monitoring is one of the most critical aspects of an owner's responsibilities. Cats often refuse food due to calicivirus mouth sores; therefore, owners should closely monitor their cats and, aware of the risks of each day they don't eat, consider alternative feeding methods. Soft wet foods, pureed foods, flavorful foods, or high-calorie supplements should be tried regularly, and the cat's preferences should be observed. The cat's water consumption should also be monitored daily; if signs of dehydration appear, veterinary assistance should be sought immediately.

Maintaining hygiene protocols is also the direct responsibility of owners. Because calicivirus can survive on surfaces for short periods, food bowls, water bowls, toys, and bedding should be cleaned and disinfected regularly. The litter box used by the infected cat should also be cleaned daily and kept inaccessible to other cats. If there are other cats in the home, adhering to the quarantine process is the most important step in breaking the chain of transmission.

Another important task for owners is to manage stress . Stress can worsen both ulcer pain and respiratory symptoms. Therefore, the cat's living space should be quiet, orderly, and safe. Stressors such as noisy activities, heavy visitor traffic, the addition of a new pet, or a move should be postponed as much as possible during the illness. Providing the cat with a warm, soft bed, a safe place to hide, and a dimly lit room will also help the cat relax psychologically.

Regular veterinary checkups are also the responsibility of owners. Regular checkups should be performed until mouth sores are completely healed, and the treatment protocol should be adjusted if necessary. For cats with chronic stomatitis, a long-term treatment plan should be developed and adhered to.

Cats infected with calicivirus can experience recurrences, so owners should establish a long-term care routine and monitor their cat's overall health regularly. This approach is most effective for maintaining the cat's quality of life and minimizing the effects of the disease.

Calicivirus Differences in Cats and Dogs

Despite the similarity in name, there is no biological, genetic, or clinical relationship between feline calicivirus infection and viral infections in dogs. Feline calicivirus (FCV) is specific to cats , while canine calicivirus is an enteric virus of low clinical significance, very rare in dogs . FCV belongs to the Vesivirus genus of the Picornaviridae family and primarily targets the upper respiratory tract, oral mucosa, and, in some variants, the joints of cats. Calicivirus-like viruses seen in dogs belong to different species and do not interact with FCV in cats; transmission from cat to dog or dog to cat is not possible.

The most prominent clinical features of calicivirus infection in cats include oral ulcers , upper respiratory tract signs , sneezing , nasal discharge , increased drooling , conjunctivitis , and, in some strains , a lameness syndrome (limping syndrome) . The severe variant, VS-FCV, can present with dramatic systemic signs such as multiorgan involvement, high fever, edema, and skin lesions. In contrast, calicivirus-like infections in dogs often produce mild enteric symptoms and are usually limited to short-term diarrhea or vomiting.

There are also significant differences between cats and dogs in terms of immune responses. FCV infection in cats can progress from an acute phase to chronic carrier status, and some cats continue to shed the virus for extended periods, creating a continuous cycle of infection, particularly in multi-cat households. In dogs, calicivirus infections tend not to become chronic, and the duration of viral shedding is quite short.

Although oral ulcers are the most characteristic finding of FCV in cats, such mucosal ulcerations in dogs are not caused by calicivirus. When oral ulcers are observed in dogs, they are often associated with immune system disorders, foreign bodies, stomatitis complexes, or other viral pathogens (e.g., distemper).

Transmission routes are also a key difference between the species. In cats, FCV spreads rapidly through saliva, nasal and eye discharge, and can survive on surfaces for days. Similar infections with enteric calicivirus in dogs are transmitted via feces , remain viable for a shorter period, and are generally of limited clinical significance. Furthermore, vaccines developed for both species only protect against the virus within their own species; the feline calicivirus vaccine does not protect dogs , and the canine enteric calicivirus vaccine has no effect on cats.

All these differences indicate that FCV in cats is a respiratory and oral mucosal infection that is completely specific to the cat species, has serious clinical effects, and is characterized by mouth sores; whereas calicivirus-like infections in dogs are viral agents of different species, milder, and of limited importance.

Frequently Asked Questions (FAQ)

What exactly is a Calicivirus infection in cats?

Calicivirus infection in cats is a highly contagious viral disease that affects the upper respiratory tract and particularly the oral mucosa; the virus produces symptoms such as painful ulcers in the mouth, pitted lesions on the tongue, increased salivation, difficulty swallowing, loss of appetite, sneezing, nasal discharge and occasionally lameness, and some variants can be severe enough to cause multi-organ involvement.

How do cats get calicivirus?

Calicivirus is most commonly transmitted to cats through infected cats' saliva, eye and nose discharge, sneeze droplets, shared food and water bowls, toys, and carriers; because the virus can survive on some surfaces for days, failure to practice hygiene after contact accelerates transmission.

What is the difference between a Calicivirus infection and FHV?

While Calicivirus infection predominantly causes mouth sores, tongue ulcers, and sometimes lameness, Feline Herpesvirus (FHV) is an infection with more pronounced eye and respiratory symptoms; Calicivirus generally causes milder nasal congestion, but oral ulcers are much more severe than with FHV.

Why do mouth sores occur in calicivirus infection?

Calicivirus produces intense viral replication in the epithelial cells of the oral mucosa; this replication causes cell destruction, inflammation, and surface tissue loss, resulting in painful ulcers on the tongue, palate, and buccal mucosa, which severely inhibit the cat's ability to eat.

Why is calicivirus infection more severe in kittens?

Because kittens' immune systems are not fully developed, Calicivirus infection progresses very quickly; mouth sores deepen, nasal discharge intensifies, malnutrition develops rapidly, and complications such as dehydration and pneumonia make the disease much more dangerous.

What are the earliest symptoms of a calicivirus infection?

The earliest signs of a calicivirus infection are sneezing, a slight fever, a runny nose, decreased appetite, and small lesions that start as dots inside the mouth; these lesions can quickly develop into ulcers, causing the cat to refuse to eat altogether.

What is the typical appearance of calicivirus mouth sores?

Calicivirus mouth sores usually appear as round, pitted, yellowish-white, sharply demarcated, very painful ulcers on the upper surface of the tongue or the buccal mucosa; the cat approaches the food bowl and smells it, then turns away from the food due to the pain.

What causes increased salivation in a calicivirus infection?

Because oral ulcers cause intense pain and irritation in the mucosa, the cat has difficulty closing its mouth and its swallowing reflex is weakened; as a result, saliva accumulation increases, the consistency of the saliva becomes darker and the cat constantly drools.

What to do when calicivirus causes loss of appetite in a cat?

Loss of appetite is a very dangerous situation in Calicivirus infection; strongly flavored wet food should be warmed and offered, soft puree-like foods should be preferred, water consumption should be increased, and if the cat does not eat for more than 24 hours, supplemental feeding or serum therapy should be administered upon the recommendation of a veterinarian.

Does calicivirus cause lameness?

Yes, some strains of Calicivirus cause inflammation in the joints, causing a lameness condition called “limping syndrome”; in this form, the cat will have difficulty walking for a few days, will have tenderness in its legs, and may refuse to move.

Does calicivirus infection affect the eyes?

Yes, some strains of FCV can cause conjunctivitis, watery eyes, redness, light sensitivity, and transient corneal surface irritation; however, eye ulcers are less common compared to FHV.

How useful is the PCR test in diagnosing calicivirus infection?

PCR testing is the most reliable method for diagnosing Calicivirus infection; it allows the disease to be distinguished from other respiratory pathogens by directly detecting the RNA of the virus in oral, nasal, or oropharyngeal swab samples.

Is there a treatment that completely eliminates Calicivirus?

No, there is no antiviral treatment that completely eliminates Calicivirus infection; however, the clinical picture can be successfully managed with supportive care, pain control, antibiotics (for secondary infections), antiseptic oral solutions, serum therapy and preparations that support the immune system.

How should a Calicivirus positive cat with mouth sores be fed?

Soft, pureed, strongly flavored, warm wet foods should be preferred; dry food options should be temporarily discontinued as they will irritate oral ulcers, and high-calorie recovery foods should be used if necessary.

How long does it take for calicivirus to spread to other cats in the household?

Calicivirus can be transmitted to cats within hours of contact; because the virus spreads primarily through saliva and nasal discharge, being in the same environment with other cats carries a high risk of transmission.

Will every cat that comes into contact with calicivirus become ill?

Not every cat that comes into contact with the virus becomes ill; cats with strong immune systems may experience mild infection or become subclinical carriers, but kittens and cats with low immunity develop severe clinical signs.

How long does calicivirus survive on surfaces?

Calicivirus is highly resistant to environmental conditions and can survive on some surfaces for several days; therefore, surface hygiene, clean feeding bowls, and regular washing of toys are critical to preventing transmission.

What causes bad breath in a cat that is calicivirus positive?

Oral ulcers, tissue breakdown, bacterial secondary infection and excessive salivation are the main causes of bad breath; this is directly proportional to the severity of oral inflammation.

Can a calicivirus infection be fatal?

While classic Calicivirus infections are usually manageable, the virulent systemic Calicivirus (VS-FCV) variant can be fatal, with severe organ failure, skin ulcers, coagulation disorders, and rapidly progressive deterioration.

Do cats carrying calicivirus always show symptoms?

No, carrier cats do not always show symptoms, but mouth sores and respiratory signs can reappear when stress, immune suppression, illness or environmental changes occur.

Is it okay to take a bath if you have a Calicivirus infection?

Bathing is not recommended as it may aggravate symptoms due to chills and stress; dirty areas should be cleaned locally with a damp cloth if necessary.

Does the calicivirus vaccine prevent the disease completely?

Although the vaccine does not completely prevent the disease, it reduces the severity of the infection, makes mouth sores milder, and significantly limits transmission to other cats by reducing viral shedding.

When should a cat infected with calicivirus be taken for a veterinary checkup?

Veterinary intervention should not be delayed when symptoms such as complete loss of appetite, enlargement of mouth sores, increased drooling, high fever, difficulty breathing, rapid weight loss or lameness are observed.

What problems can calicivirus cause when it becomes chronic?

Chronic Calicivirus infection can lead to long-term problems that reduce the quality of life, such as persistent inflammation in the mouth, gingivostomatitis, persistent bad breath, recurrent ulcer formation, chronic runny nose, frequent sneezing and nutritional disorders.

How does stress affect cats with a calicivirus infection?

Because stress suppresses the immune system, it causes mouth sores to deepen, ulcer healing to be delayed, and viral replication to accelerate; therefore, the sick cat's environment should be calm, safe, and low-stress.

Sources

• Cat Fanciers' Association (CFA)

• The International Cat Association (TICA)

• American Veterinary Medical Association (AVMA)

• Mersin Vetlife Veterinary Clinic – Open on Map: https://share.google/XPP6L1V6c1EnGP3Oc