Feline Coronavirus

Information/Facts
Infection
Clinical Signs
Diagnosis
Treatment
Prognosis
Prevention
caronavirus(pp)                                 cat in brush(qq)                                     colour carona(rr)

Information/Facts
FCoV is a virus that is grouped into the Coronaviridae family. Being part of this family of viruses, characteristics that are prominent to FCoV include having an envelope, and containing a positive, single stranded RNA genome.  Coronaviruses are larger than most RNA viruses, and are named because they appear to resemble a crown when viewed under electron microscopy.  Upon release from the viral nucleocapsid after entry in to the host cell, the viral RNA uses the host mechanisms to translate and transcribe the RNA to build and assemble new viral units. (19, 20)


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anxious(tt)

FCoV is a common viral infection in cats that has varying degrees of virulence.  These range from the highly virulent Feline Infectious Peritonitis virus (FIPV) to strains that cause an enteric disease (FECV), to asymptomatic infections.   The virus that causes FIP is a mutant strain of FECV. The virus starts by infecting the epithelium of the intestine and local lymph nodes. After detection and targeting by the cat’s immune system, infected cells are engulfed by macrophages, but are not destroyed like they should be. This results in the spread of the virus throughout the body. Development of the FIP disease can take on 2 forms, wet and dry, and involve multiple body systems, which makes diagnosis difficult.  (3, 21, 22, 23, 24)
                                                                                                                                    
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Infection
 

A majority of cats that become infected with FCoV recover, but a few become carriers of the virus, and of those, a small number develop the lethal disease FIP due to a mutation in the virus which can occur anywhere from weeks to years after the initial infection.   (21)

 litter humour(uu)

FCoV-infected cats have the virus present in bodily fluids (blood, feces, saliva, and milk), and transmission is mainly by the oral route, or less frequently, by inhalation of aerosolized viral particles; both these methods require close contact. Cats can also be infected if exposed to contaminated surfaces that include, but are not exclusive to, clothing, bedding, toys, or feeding and watering dishes.  In litter boxes, research shows that FCoV can survive and be infective anywhere from several days to 7 weeks in dried fecal matter. This can produce problems in clearing the virus and preventing transmission in multicat homes, catteries, or to homes looking to replace an individual that has passed on.   (21, 22, 25)

                                                                                       FCoV cyclel(vv)

The FIP disease is acquired when a mutant variation of FCoV is unmanageable by the immune system. This results in the cat being classified as a “carrier” because they are persistently infected with no clinical signs, but are able to shed large amounts of FCoV in their feces.  Shedding of the virus is elevated for the first 2-4weeks following infection with FIP disease, but is followed by a cessation of shedding along with the absence of clinical signs until the cat is stressed at a future date (weeks, months, or years later).   (32, 26, 27)

                                                                                            wet form(ww)

The wet form, also know as the effusive form, is so called because there is an accumulation of fluid within either the chest or abdominal cavity. It has been suggested that the cause of the wet form is a result of antigen-antibody complexes that form and are deposited in and severely damage blood vessels, along with an insufficient cell-mediated response to clear the complexes.  The dry form, also known as the non-effusive form, has minimal to no fluid accumulation, but infects organs where it is deposited (brain and central nervous system, liver, and kidneys). It is suggested that the dry form is due to a more effective cell-mediated immunity.   (22, 28, 29)   

Although FCoV is a common viral infection among cats, the disease of FIP is most serous amongst the young (<2yrs) and old (>10yrs) cats or to cats with  a compromised immune system (due to poor body condition, concurrent infection or increased stress all which increase susceptibility to the disease).    (23)
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Clinical Signs

Clinical signs that are used for FCoV infection, or to determine if a cat has FIP, are varied due to the number of body systems that can be involved. Signs are also considered to be non-specific, as many infections and diseases have similar symptoms (fever, loss of appetite, and weight loss). Initial signs range from mild upper respiratory signs similar to the flu with sneezing, watery eyes and nose, to mild intestinal problems with diarrhea.  As certain organ systems are affected, signs closely related to those organs can become more noticeable.

For example, the wet form with increase amounts of fluid in body cavities results in the animal developing breathing difficulties or an appearance of being bloated or distended.

asites and fluid(xx)                          uveitis dryform(yy)

Signs of the dry form of FIP include poor body and coat condition, yellow dis-coloured mucous membranes, neurological signs, and dry eyes which may also have increased brown discolouration of the iris.  (21, 23, 29)
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Diagnosis
There are numerous tests that can be run on blood or feces to determine the presence of FCoV (ELISA, indirect immunofluorescence assay, virus-neutralization, and PCR) in the cat, and some are able to quantify the antibodies (HAI serum dilutions); however these tests do not aid in a diagnosis of FIP despite a positive test for the virus, or for high number of antibodies.   (21)

fip cytology(zz)

Due to the lack of tests that specifically diagnose the disease of FIP, veterinarians have relied on a variety of tests for different aspects of the disease which can include blood work analysis, other body fluid analysis, radiographic imaging, and biopsies of organs possibly affected.   (23)

Recently at the University of Glasgow, Dr. Addie has developed a four part test which she claims to be able to diagnose FIP disease with 90% accuracy.  The parts of the test include a FCoV antibody titre, an albumin:globulin ratio on collected effusion or plasma, an alpha 1 – acid glycoprotein level, and finally either cytology or hematology.   (29)

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Treatment

At this time there is no cure for cats infected with the mutant variant of FCoV that cause the disease FIP.  This unfortunately means that a diagnosis of FIP will eventually have a fatal outcome.  Cats with confirmed FIP are often given supportive care to ease the pain of the immune response and inflammatory reaction of this disease, and should be fed a balanced diet that provides the necessary nutrition.

A pharmalogical combination of steroids, antibiotics, appetite stimulants and targeted cellular death has been attempted with mixed results, but there is hope for the future with drug combinations that includes antivirals. (21)

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Prognosis

Prognosis is very poor for cats with confirmed FIP as the virus affects multiple systems, which results in recovery being rare.

Cats with clinical signs of the wet form of FIP usually survive only for a few days to weeks but do not survive more than eight months; cats with clinical signs of the dry form usually only survive a few weeks but can potentially survive over a year.  (21, 23)

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Prevention

A vaccine offers protection from the coronavirus, which in turn decreases the chance of a cat developing FIP. Lowering risk factors such as overcrowding, maintaining an appropriate level of nutrition and sanitation, and testing before the introduction of new members will aid in lowering the prevalence of FIP. Consultation with your vet to discuss your own circumstances will help provide the best protection for your cat.   (21, 23)

One vaccine is current available, but has had mixed reviews on efficacy of protection.  The vaccine is generally not recommended and is suggested only for individuals that have never been exposed to FCoV and in an environment where the virus is considered to be prevalent. The modified live vaccine is administered intranasally to cats 16 weeks of age or older.    (3)

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