Feline Coronavirus (FCoV) is a common viral infection found in cat populations globally. It belongs to the Alphacoronavirus suis species, which includes coronaviruses affecting canines and swine. FCoV infections are frequently mild or asymptomatic. Despite its prevalence, FCoV does not infect humans.
Forms of Feline Coronavirus
Feline Coronavirus exists in two main forms. The most common is Feline Enteric Coronavirus (FECV), which primarily infects intestinal cells. FECV infections are generally benign, often causing no symptoms or only mild, temporary gastrointestinal upset. Most infected cats clear the virus, but some may become persistent carriers, shedding it in their feces.
In a smaller percentage of cases, typically 3-10% of infected cats, FECV can undergo a genetic mutation. This mutation transforms FECV into Feline Infectious Peritonitis Virus (FIPV), which causes Feline Infectious Peritonitis (FIP). FIPV differs from FECV by gaining the ability to infect and replicate within macrophages, immune cells, leading to widespread systemic inflammation.
FIP manifests in two primary forms: effusive (wet) FIP and non-effusive (dry) FIP. Wet FIP, accounting for 60-70% of cases, is characterized by fluid accumulation in body cavities. Dry FIP involves granuloma formation in various organs like the liver, kidneys, brain, or eyes without significant fluid buildup.
How Feline Coronavirus Spreads and What to Look For
Feline Coronavirus primarily spreads through the fecal-oral route. Cats become infected by ingesting virus-contaminated feces, often through shared litter boxes, grooming, or contact with contaminated objects and environments. Multi-cat environments, such as catteries or shelters, have higher transmission rates. Infected cats, even those without symptoms, can shed the virus in their feces for weeks to months, and some become indefinite carriers. Kittens tend to shed higher levels of the virus than adult cats.
Clinical signs of FCoV infection vary. Cats infected with FECV are often asymptomatic or may experience mild, temporary diarrhea and vomiting. These gastrointestinal signs are typically self-limiting and resolve without treatment.
In contrast, FIP presents with a range of severe, progressive symptoms. Initial signs can include persistent fever unresponsive to antibiotics, lethargy, decreased appetite, and weight loss or muscle wasting. For cats with effusive (wet) FIP, fluid accumulation in the abdomen can lead to a swollen belly, while fluid in the chest cavity may cause labored breathing.
Cats with non-effusive (dry) FIP may show signs related to organ inflammation, such as neurological issues (incoordination, seizures), ocular lesions (uveitis), or granulomas in internal organs. Jaundice (yellowish skin and eyes) can also be present in both forms.
Identifying and Addressing Feline Coronavirus
Diagnosing FCoV infection is not always straightforward, as many cats are asymptomatic or have mild, self-resolving symptoms. Diagnosing Feline Infectious Peritonitis (FIP) is complex due to its varied and non-specific clinical signs, often requiring multiple diagnostic tools. Veterinarians may use blood tests to look for abnormalities like elevated globulin levels, a low albumin-to-globulin ratio (less than 0.6), and elevated total serum protein. These findings are suggestive but not definitive, as other conditions can cause similar blood changes.
Diagnostic imaging, like ultrasound or X-rays, can help detect fluid accumulation typical of wet FIP or identify organ enlargement and granulomatous changes in dry FIP. If fluid is present, a sample can be collected and analyzed. FIP fluid is often yellowish, mucinous, with high protein and low cellularity. A Rivalta test, a simple in-house test, can differentiate fluid types; an exudate suggests FIP.
Specific tests like Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) can detect FCoV RNA in tissue, fluid, or cerebrospinal fluid samples, which supports an FIP diagnosis, especially with high viral loads. However, RT-PCR on fecal samples only indicates FCoV shedding and does not confirm FIP. A definitive FIP diagnosis often relies on immunohistochemistry, detecting FCoV antigen in tissue biopsies.
Historically, FIP was considered almost uniformly fatal once clinical signs developed. However, the treatment landscape for FIP has evolved with antiviral therapies. Nucleoside analogs like GS-441524 and its prodrug remdesivir inhibit viral replication, showing promise in treating FIP.
While not all treatments are universally approved or available, these antiviral drugs have demonstrated high success rates, with recovery rates often exceeding 80-90%. Oral GS-441524 is commonly used, with treatment courses often lasting around 84 days. Treatment decisions should be made in consultation with a veterinarian, who can guide on available options and protocols.
Preventing Feline Coronavirus and Prognosis
Preventing the spread of Feline Coronavirus, especially in multi-cat environments, relies on strict hygiene practices. Frequent cleaning and disinfection of litter boxes are important, ideally daily, with weekly disinfection. Providing an adequate number of litter boxes (one more than the number of cats) can reduce viral load. Reducing stress in multi-cat households, ensuring separate food and water bowls, and cleaning long-haired cats’ hind ends can also help minimize fecal contamination. FCoV is fragile and can be inactivated by most commercial disinfectants, though it can survive indoors for up to seven weeks under dry conditions.
A FCoV vaccine is available, administered intranasally. However, its efficacy is limited. It is recommended only for high-risk populations, such as breeding catteries or multi-cat facilities, and for FCoV antibody-negative kittens at least 16 weeks old. The vaccine does not prevent FIP and is not universally recommended by veterinary associations. Limiting exposure to stray cats and responsible cat ownership also contribute to prevention.
The prognosis for cats infected with the enteric form of Feline Coronavirus (FECV) is excellent. Most cats remain asymptomatic or experience mild, self-limiting gastrointestinal signs, recovering fully without treatment. For cats that develop Feline Infectious Peritonitis (FIP), the prognosis was historically grim, being progressive and almost always fatal. However, with the advent of new antiviral treatments, the outlook has improved. While FIP remains a serious condition, these emerging therapies offer hope for remission and improved survival rates, shifting FIP from a uniformly fatal disease to one that can be managed.