What is the Feline Coronavirus (FCoV)?
Did you know that cats can get the Coronavirus?
Due to the current situation with COVID19, I thought I would discuss coronavirus in cats. Coronaviruses make up a large group of viruses divided into four families. Coronavirus infections manifest very differently in each species. Humans cannot be infected with FCoV as it’s a different strain of coronavirus than COVID19. Based on current research, COVID19 has not been shown to be transmitted from humans to pets. FCoV is an enveloped, single-stranded RNA virus that is common throughout the world in domestic cats with 40% of household cats and up to 90% of cats in catteries testing positive for coronavirus antibodies.
Symptoms and Transmission of the Feline Coronavirus
The FCoV is a highly prevalent viral infection worldwide and infections often go unnoticed. The coronavirus is typically transmitted via the fecal-oral route. Approximately one third of infected cats shed viral material in their feces for a couple months after infection. A small percentage of asymptomatic cats become carriers and will continually shed the virus throughout their life. Transmission can also occur if a cat is exposed to clothing or other objects that have recently come in contact with the virus. Typically, the virus survives in the environment for 24-36 hours, however, there is evidence that it can survive much longer in cold temperatures. Cats housed with several others, such as at boarding facilities or shelters have an increased risk of exposure.
Infected cats are usually asymptomatic or develop mild, self-limiting respiratory and gastrointestinal symptoms, such as nasal and ocular discharge, vomiting and diarrhea.
What Happens When the Feline Coronavirus Mutates?
A small percentage of cats with FCoV develop a fatal condition called feline infectious peritonitis (FIP). The development of FIP from FCoV is not well understood, however, the disease occurs more frequently in cats less than 2 years of age. There are different theories about how FCoV mutates into the virulent FIP. One theory postulates that FCoV replicates within enterocytes (cells that line the small and large intestines) and eventually a mutation occurs in a certain region of the genome that allows it to replicate within macrophages (type of blood cell). Another theory suggests that FCoV and FIP are caused by two different strains which suggests that development of FIP depends upon the strain that the cat is infected with and the cat’s immune response. Replication of the virus within macrophages is the critical step in developing FIP. If the cat is unable to clear all infected macrophages, the resulting immune response is fatal.
Clinical Symptoms of FIP Include...
- fever
- weight loss
- anorexia
- lethargy
- depression
- diarrhea
- distended fluid-filled abdomen
- labored breathing
- icteric (yellowish) mucous membranes from liver disease
- changes in behavior
How is FIP Diagnosed?
FIP is difficult to diagnose because there is currently no single diagnostic test available that is able to differentiate between antibodies produced against the FCoV and FIP. Most cats have been exposed to the FCoV therefore identifying the presence of FCoV antibodies is not diagnostic. In fact, a blood test performed on FIP+ cats may come back negative for coronavirus antibodies because of a reduction of detectable antibody concentrations. In addition, diagnostic test results that commonly occur in FIP+ cat are also indicative of other pathologies, such as liver and kidney disease.
FIP can manifest in a “wet” or “dry” form. Distinguishing between the two forms is important to determine the best diagnostic approach. Cats who develop the “wet” form may accumulate fluid in their chest and/or abdominal cavity. In these cases, a fluid sample can be taken and evaluated. The fluid has a characteristic protein content that is sticky and straw-colored. The “dry” form involves various organs, including the liver and intestines.
A few tests are available to detect the presence of the virus in tissue and/or fluid samples, however, none of these tests can definitively diagnose FIP due to false negative and false positive results. In combination, diagnostic tests can indicate a FIP diagnosis. A diagnosis largely relies on patient history, clinical symptoms, histopathology (tissue sample), a complete blood count, chemistry panel and other supportive diagnostic results, including…
- Immnohistochemical test is able to detect viral proteins in infected white blood cells in a tissue sample.
- Immunofluorescence test detects viral proteins in infected white blood cells in tissue or body fluid samples.
- Polymerase Chain Reaction (PCR) detects viral genetic material in tissue or body fluids.
- FCoV antibody tests
What is the Prognosis for FIP infected cats?
Unfortunately, the prognosis is pretty grim for cats who develop FIP. Currently, there is no cure or lifesaving treatment for FIP. The cat should be provided with supportive care such as fluids and anti-inflammatories. Humane euthanasia may also be elected if the cat’s quality of life has significantly decreased. Kittens are more likely to be infected and contribute to the spread of the virus. Communal living cats are at much higher risk (1-5%) of becoming infected with FCoV compared to 0.3% of all cats.
Although FIP is currently a fatal condition, there is hope for a future treatment. The Journal of the American Veterinary Medical Association (JAVMA) posted an article stating that recent studies of two antiviral drugs (GS-441524 and GC376) have shown promising results for the treatment of FIP. A recent clinical study was performed to evaluate safety and efficacy of the nucleoside analog GS-441524. In this study, 25 out of 31 FIP+ cats responded well to treatment. Researchers said the safety profile was exceptional. Studies of GC376, a viral protease inhibitor, have proven less effective than GS-441524. Young cats receiving GC376 experienced developmental abnormalities of their permanent teeth. However, researchers state that additional clinical trials need to be performed before a final conclusion about each drug can be made.
It is true that there is still no cure, or totally effective prevention. But we understand the virus and the infection much better now. We have new tools that allow us to look at viruses at the molecular level. Any knowledge about the virus and how the host cat responds to it will have influence down the road.
Is FIP Preventable?
If an infected cat is removed from living situations with multiple cats, this can prevent the spread of the virus as well as a possible mutation into a deadly FIP. Unfortunately most cats infected with FCoV are asymptomatic. In addition, the virus can remain dormant in the body for months or years with no signs or symptoms of disease.
There is currently one FIP vaccine available in North America, however, the effectiveness of the vaccine has been variable. Consequently, it is not recommended by the American Association of Feline Practitioners Feline Vaccine Advisory Panel.