Feline calicivirus
Encyclopedia
Feline calicivirus is a virus
of the family Caliciviridae
that causes disease in cat
s. It is one of the two important viral causes of respiratory infection in cats, the other being feline herpesvirus
. FCV can be isolated from about 50 percent of cats with upper respiratory infection. Cheetah
s are the other species of the family Felidae
known to become infected naturally.
(the degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host). Being an RNA virus
, FCV has a high elasticity of its genome
which makes it more adaptable to environmental pressures. This not only makes the development of vaccines more difficult, but allows for the development of more virulent
strains. In persistently infected cats, it has been shown that the gene
for the major structural protein of the viral capsid
(the outer protein coat of a mature virus) evolves through immune-mediated positive selection
and allows the virus to escape detection by the immune system
.
A form of FCV has been found to cause a particularly severe systemic disease in cats, similar to rabbit hemorrhagic disease (which is also caused by a calicivirus). This virus has been called virulent systemic feline calicivirus (VS-FCV) or FCV-associated virulent systemic disease (VSD). The disease is caused by direct viral invasion of epithelium
and endothelium
and secondary host immune response. It seems that strains of VS-FCV have risen independently of one another since first being described, meaning that not all cases of VS-FCV have spread from a single case. Most of the outbreaks of VS-FCV have been reported in the United States
. It was originally described in 1998 in Northern California
.
The prevalence
of FCV varies depending on the environment. In private households, FCV is present in about 10 percent of cats (either in active or carrier state), while the prevalence in shelters or catteries is 25 to 40 percent.
FCV replicates in the oral and respiratory tissues and is secreted in saliva
, feces
, urine
, and respiratory secretions. It can be transmitted through the air, orally, and on fomite
s. Infected cats usually shed the virus for two weeks. Following this period, infected cats never shed the virus again or become latently infected and shed the virus continuously or intermittently. Coinfection
with either feline herpesvirus
or feline immunodeficiency virus
causes a more severe disease.
, nasal discharge, sneezing, and ulceration of the mouth (stomatitis
). Pneumonia
may develop with secondary bacteria
l infections. In addition to stomatitis, some cats may develop a polyarthritis
, both probably immune-mediated through immune complex
deposition. Stomatitis and polyarthritis can develop without any upper respiratory infection symptoms, but fever and loss of appetite may occur. Less commonly, glomerulonephritis
can develop in chronic cases secondary to immune complex deposition. The great variability of symptoms in individual cases of FCV is related to the relative virulence of different strains of the virus.
VS-FCV can cause a rapid epidemic
with a mortality rate of up to 67 percent. Initial symptoms include discharge from the eyes and nose, ulceration in the mouth, anorexia, and lethargy, and occur in the first one to five days. Later symptoms include fever, edema
of the limbs and face, jaundice
, and multiple organ dysfunction syndrome
.
Diagnosis of FCV is difficult without specific tests because the symptoms are similar to other feline respiratory diseases, especially feline viral rhinotracheitis
. The presence of stomatitis may indicate FCV. Specific tests include virus culture
, polymerase chain reaction
(PCR), and immunohistochemical stain
ing.
s are used for secondary bacterial infections and immune modulators, such as Lymphocyte T-Cell Immune Modulator
has been used for immune support. Nursing care and rehydration are used for dehydrated and anorexic
cats. Corticosteroid
s or azathioprine
may be used for polyarthritis. Stomatitis
is very difficult to treat. Antibiotics, corticosteroids, and tooth extractions all have been used with varying success. Cats on corticosteroids must be monitored carefully for worsening of any upper respiratory infection.
Natural immunity from maternal antibodies lasts in the kitten from three to nine weeks. After that, kittens are susceptible to FCV. Previous infection does not guarantee lifelong immunity, since an antigenically dissimilar FCV (such as VS-FCV) can cause infection. However, usually after the age of three years FCV infections are mild or asymptomatic. FCV vaccination
will not always prevent disease but will reduce the severity. FCV vaccines come in two types, inactivated (ATCvet code: ) and attenuated (live, but not virulent; in various combination vaccines). They have been shown to be effective for at least three years. Attenuated FCV vaccine has been shown to possibly cause mild upper respiratory infection. Inactivated vaccine does not, but it causes more local inflammation and possibly predisposes the cat to vaccine-associated sarcoma
. The only vaccine licensed for prevention of VS-FCV is CaliciVax, manufactured by Fort Dodge Animal Health, a division of Wyeth
. It also contains a strain of the traditional FCV virus. Since VS-FCV has arisen from variant strains of FCV, it is not certain that a vaccine for one virulent strain will protect against all virulent strains.
Quarantine
is best for control of FCV in catteries
and kennels. However, FCV is very contagious and latently infected cats will continue to shed virus, so complete control is difficult. An outbreak of VS-FCV at a humane society
in Missouri
in 2007 led to the euthanasia
of the entire cat population (almost 200 cats) in order to contain it. FCV may survive several days to weeks in a dry environment and longer in a cooler, wet environment. Quaternary ammonium compound
s are not thought to be completely effective, but a 1:32 dilution of household bleach
used with a detergent and sufficient contact time does seem to kill the virus.
in humans, FCV has been used as a surrogate for it in research. For instance, studies have been done on the survival of FCV in foodstuffs, the effectiveness of handwashing on FCV removal, and the use of ozone
gas to inactivate FCV found in hotel rooms, cruise ship cabins, and healthcare facilities. It is also used in general Caliciviridae research due to its being one of the few of that group of viruses that grows well in vitro
.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
of the family Caliciviridae
Caliciviridae
The Caliciviridae family are a family of viruses, members of Class IV of the Baltimore scheme. They are positive-sense, single stranded RNA which is non-segmented. The caliciviruses have been found in a number of organisms such as humans, cattle, pigs, cats, chickens, reptiles, dolphins and...
that causes disease in cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s. It is one of the two important viral causes of respiratory infection in cats, the other being feline herpesvirus
Feline viral rhinotracheitis
Feline viral rhinotracheitis is an upper respiratory infection of cats caused by feline herpesvirus 1, of the family Herpesviridae. It is also known as feline influenza and feline coryza. Viral respiratory diseases in cats can be serious, especially in catteries and kennels...
. FCV can be isolated from about 50 percent of cats with upper respiratory infection. Cheetah
Cheetah
The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...
s are the other species of the family Felidae
Felidae
Felidae is the biological family of the cats; a member of this family is called a felid. Felids are the strictest carnivores of the thirteen terrestrial families in the order Carnivora, although the three families of marine mammals comprising the superfamily pinnipedia are as carnivorous as the...
known to become infected naturally.
Viral structure and pathogenesis
There are different strains of FCV that vary in virulenceVirulence
Virulence is by MeSH definition the degree of pathogenicity within a group or species of parasites as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenicity of an organism - its ability to cause disease - is determined by its...
(the degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host). Being an RNA virus
RNA virus
An RNA virus is a virus that has RNA as its genetic material. This nucleic acid is usually single-stranded RNA but may be double-stranded RNA...
, FCV has a high elasticity of its genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
which makes it more adaptable to environmental pressures. This not only makes the development of vaccines more difficult, but allows for the development of more virulent
Virulence
Virulence is by MeSH definition the degree of pathogenicity within a group or species of parasites as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenicity of an organism - its ability to cause disease - is determined by its...
strains. In persistently infected cats, it has been shown that the gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
for the major structural protein of the viral capsid
Capsid
A capsid is the protein shell of a virus. It consists of several oligomeric structural subunits made of protein called protomers. The observable 3-dimensional morphological subunits, which may or may not correspond to individual proteins, are called capsomeres. The capsid encloses the genetic...
(the outer protein coat of a mature virus) evolves through immune-mediated positive selection
Directional selection
In population genetics, directional selection is a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction...
and allows the virus to escape detection by the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
.
A form of FCV has been found to cause a particularly severe systemic disease in cats, similar to rabbit hemorrhagic disease (which is also caused by a calicivirus). This virus has been called virulent systemic feline calicivirus (VS-FCV) or FCV-associated virulent systemic disease (VSD). The disease is caused by direct viral invasion of epithelium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
and endothelium
Endothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
and secondary host immune response. It seems that strains of VS-FCV have risen independently of one another since first being described, meaning that not all cases of VS-FCV have spread from a single case. Most of the outbreaks of VS-FCV have been reported in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. It was originally described in 1998 in Northern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
.
The prevalence
Prevalence
In epidemiology, the prevalence of a health-related state in a statistical population is defined as the total number of cases of the risk factor in the population at a given time, or the total number of cases in the population, divided by the number of individuals in the population...
of FCV varies depending on the environment. In private households, FCV is present in about 10 percent of cats (either in active or carrier state), while the prevalence in shelters or catteries is 25 to 40 percent.
FCV replicates in the oral and respiratory tissues and is secreted in saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
, feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
, urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
, and respiratory secretions. It can be transmitted through the air, orally, and on fomite
Fomite
A fomite is any inanimate object or substance capable of carrying infectious organisms and hence transferring them from one individual to another. A fomite can be anything...
s. Infected cats usually shed the virus for two weeks. Following this period, infected cats never shed the virus again or become latently infected and shed the virus continuously or intermittently. Coinfection
Coinfection
In parasitology, coinfection is the term used to describe the simultaneous infection of a host by multiple pathogen species. In virology, coinfection can also refer to the simultaneous infection of a single cell by two or more virus particles...
with either feline herpesvirus
Feline viral rhinotracheitis
Feline viral rhinotracheitis is an upper respiratory infection of cats caused by feline herpesvirus 1, of the family Herpesviridae. It is also known as feline influenza and feline coryza. Viral respiratory diseases in cats can be serious, especially in catteries and kennels...
or feline immunodeficiency virus
Feline immunodeficiency virus
Feline immunodeficiency virus is a lentivirus that affects domesticated housecats worldwide and is the causative agent of feline AIDS. From 2.5% up to 4.4% of cats worldwide are infected with FIV...
causes a more severe disease.
Symptoms
Symptoms in cats infected with FCV may develop acutely, chronically, or not at all. Latent (hidden and not obvious at the moment, but which may develop further in the future) or subclinical infections often become symptomatic when the cat is stressed, such as at the time of adoption. Acute symptoms of FCV include fever, conjunctivitisConjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...
, nasal discharge, sneezing, and ulceration of the mouth (stomatitis
Stomatitis
Stomatitis is an inflammation of the mucous lining of any of the structures in the mouth, which may involve the cheeks, gums, tongue, lips, throat, and roof or floor of the mouth...
). Pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
may develop with secondary bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
l infections. In addition to stomatitis, some cats may develop a polyarthritis
Polyarthritis
Polyarthritis is any type of arthritis which involves 5 or more joints simultaneously. It is usually associated with autoimmune conditions.Polyarthritis may be experienced at any age and is not gender specific.-Causes:...
, both probably immune-mediated through immune complex
Immune complex
An immune complex is formed from the integral binding of an antibody to a soluble antigen. The bound antigen acting as a specific epitope, bound to an antibody is referred to as a singular immune complex....
deposition. Stomatitis and polyarthritis can develop without any upper respiratory infection symptoms, but fever and loss of appetite may occur. Less commonly, glomerulonephritis
Glomerulonephritis
Glomerulonephritis, also known as glomerular nephritis, abbreviated GN, is a renal disease characterized by inflammation of the glomeruli, or small blood vessels in the kidneys...
can develop in chronic cases secondary to immune complex deposition. The great variability of symptoms in individual cases of FCV is related to the relative virulence of different strains of the virus.
VS-FCV can cause a rapid epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
with a mortality rate of up to 67 percent. Initial symptoms include discharge from the eyes and nose, ulceration in the mouth, anorexia, and lethargy, and occur in the first one to five days. Later symptoms include fever, edema
Edema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
of the limbs and face, jaundice
Jaundice
Jaundice is a yellowish pigmentation of the skin, the conjunctival membranes over the sclerae , and other mucous membranes caused by hyperbilirubinemia . This hyperbilirubinemia subsequently causes increased levels of bilirubin in the extracellular fluid...
, and multiple organ dysfunction syndrome
Multiple organ dysfunction syndrome
Multiple organ dysfunction syndrome ', previously known as multiple organ failure or multisystem organ failure , is altered organ function in an acutely ill patient requiring medical intervention to achieve homeostasis...
.
Diagnosis of FCV is difficult without specific tests because the symptoms are similar to other feline respiratory diseases, especially feline viral rhinotracheitis
Feline viral rhinotracheitis
Feline viral rhinotracheitis is an upper respiratory infection of cats caused by feline herpesvirus 1, of the family Herpesviridae. It is also known as feline influenza and feline coryza. Viral respiratory diseases in cats can be serious, especially in catteries and kennels...
. The presence of stomatitis may indicate FCV. Specific tests include virus culture
Microbiological culture
A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture media under controlled laboratory conditions. Microbial cultures are used to determine the type of organism, its abundance in the sample being tested,...
, polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....
(PCR), and immunohistochemical stain
Immunohistochemistry
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...
ing.
Treatment and prevention
There is no specific treatment for FCV. AntibioticAntibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
s are used for secondary bacterial infections and immune modulators, such as Lymphocyte T-Cell Immune Modulator
Lymphocyte T-Cell Immune Modulator
Lymphocyte T-Cell Immune Modulator is an immune regulating polypeptide manufactured by T-Cyte Therapeutics and distributed by . Lymphocyte T-Cell Immune Modulator is a potent regulator of CD-4 lymphocyte production and function. It has been shown to increase lymphocyte numbers and Interleukin-2 ...
has been used for immune support. Nursing care and rehydration are used for dehydrated and anorexic
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...
cats. Corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s or azathioprine
Azathioprine
Azathioprine is a purine analogue immunosuppressive drug. It is used to prevent organ rejection following organ transplantation and to treat a vast array of autoimmune diseases, including rheumatoid arthritis, pemphigus, inflammatory bowel disease , multiple sclerosis, autoimmune hepatitis, atopic...
may be used for polyarthritis. Stomatitis
Stomatitis
Stomatitis is an inflammation of the mucous lining of any of the structures in the mouth, which may involve the cheeks, gums, tongue, lips, throat, and roof or floor of the mouth...
is very difficult to treat. Antibiotics, corticosteroids, and tooth extractions all have been used with varying success. Cats on corticosteroids must be monitored carefully for worsening of any upper respiratory infection.
Natural immunity from maternal antibodies lasts in the kitten from three to nine weeks. After that, kittens are susceptible to FCV. Previous infection does not guarantee lifelong immunity, since an antigenically dissimilar FCV (such as VS-FCV) can cause infection. However, usually after the age of three years FCV infections are mild or asymptomatic. FCV vaccination
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
will not always prevent disease but will reduce the severity. FCV vaccines come in two types, inactivated (ATCvet code: ) and attenuated (live, but not virulent; in various combination vaccines). They have been shown to be effective for at least three years. Attenuated FCV vaccine has been shown to possibly cause mild upper respiratory infection. Inactivated vaccine does not, but it causes more local inflammation and possibly predisposes the cat to vaccine-associated sarcoma
Vaccine-associated sarcoma
A vaccine-associated sarcoma is a type of malignant tumor found in cats that has been linked to certain vaccines. VAS has become a concern for veterinarians and cat owners alike and has resulted in changes in recommended vaccine protocols...
. The only vaccine licensed for prevention of VS-FCV is CaliciVax, manufactured by Fort Dodge Animal Health, a division of Wyeth
Wyeth
Wyeth, formerly one of the companies owned by American Home Products Corporation , was a pharmaceutical company. The company was based in Madison, New Jersey, USA...
. It also contains a strain of the traditional FCV virus. Since VS-FCV has arisen from variant strains of FCV, it is not certain that a vaccine for one virulent strain will protect against all virulent strains.
Quarantine
Quarantine
Quarantine is compulsory isolation, typically to contain the spread of something considered dangerous, often but not always disease. The word comes from the Italian quarantena, meaning forty-day period....
is best for control of FCV in catteries
Cattery
There are two types of cattery, boarding cattery and breeding cattery.A boarding cattery is where cats are housed temporarily when they can't stay at their owners' home...
and kennels. However, FCV is very contagious and latently infected cats will continue to shed virus, so complete control is difficult. An outbreak of VS-FCV at a humane society
Humane Society
A humane society may be a group that aims to stop human or animal suffering due to cruelty or other reasons, although in many countries, it is now used mostly for societies for the prevention of cruelty to animals...
in Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
in 2007 led to the euthanasia
Animal euthanasia
Animal euthanasia is the act of putting to death painlessly or allowing to die, as by withholding extreme medical measures, an animal suffering from an incurable, especially a painful, disease or condition. Euthanasia methods are designed to cause minimal pain and distress...
of the entire cat population (almost 200 cats) in order to contain it. FCV may survive several days to weeks in a dry environment and longer in a cooler, wet environment. Quaternary ammonium compound
Quaternary ammonium cation
Quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure NR4+, R being an alkyl group or an aryl group. Unlike the ammonium ion and the primary, secondary, or tertiary ammonium cations, the quaternary ammonium cations are permanently charged,...
s are not thought to be completely effective, but a 1:32 dilution of household bleach
Bleach
Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...
used with a detergent and sufficient contact time does seem to kill the virus.
Use in research
Because of the similarity of FCV to Norovirus, a common cause of gastroenteritisGastroenteritis
Gastroenteritis is marked by severe inflammation of the gastrointestinal tract involving both the stomach and small intestine resulting in acute diarrhea and vomiting. It can be transferred by contact with contaminated food and water...
in humans, FCV has been used as a surrogate for it in research. For instance, studies have been done on the survival of FCV in foodstuffs, the effectiveness of handwashing on FCV removal, and the use of ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
gas to inactivate FCV found in hotel rooms, cruise ship cabins, and healthcare facilities. It is also used in general Caliciviridae research due to its being one of the few of that group of viruses that grows well in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...
.