Feline viral rhinotracheitis
Encyclopedia
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 caused by feline herpesvirus 1, of the family Herpesviridae
Herpesviridae
The Herpesviridae are a large family of DNA viruses that cause diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word herpein , referring to the latent, recurring infections typical of this group of viruses...
. It is also known as feline influenza and feline coryza. Viral
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...
respiratory diseases in cats can be serious, especially 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 kennel
Kennel
A kennel is the name given to any structure or shelter for dogs. A kennel is a doghouse, run, or other small structure in which a dog is kept...
s. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is feline calicivirus
Feline calicivirus
Feline calicivirus is a virus of the family Caliciviridae that causes disease in cats. 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...
.
FVR is very contagious and can cause severe disease, including death from 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...
in young kittens. All members of the 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...
family are susceptible to FVR; in fact, FHV-1 has caused a fatal encephalitis
Encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...
in lion
Lion
The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...
s in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
Transmission
FVR is transmitted through direct contact only. It replicates in the nasal and nasopharyngealNasopharynx
The nasopharynx is the uppermost part of the pharynx. It extends from the base of the skull to the upper surface of the soft palate; it differs from the oral and laryngeal parts of the pharynx in that its cavity always remains patent .-Lateral:On its lateral wall is the pharyngeal ostium of the...
tissues and the tonsil
Tonsil
Palatine tonsils, occasionally called the faucial tonsils, are the tonsils that can be seen on the left and right sides at the back of the throat....
s. Viremia
Viremia
Viremia is a medical condition where viruses enter the bloodstream and hence have access to the rest of the body. It is similar to bacteremia, a condition where bacteria enter the bloodstream.- Primary versus Secondary :...
(the presence of the virus in the blood) is rare. The virus is shed
Viral shedding
Viral shedding refers to the successful reproduction, expulsion, and host-cell infection caused by virus progeny. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell by several methods.The term is used...
in saliva and eye and nasal secretions, and can also be spread by 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. FVR has a two to five day incubation period
Incubation period
Incubation period is the time elapsed between exposure to a pathogenic organism, a chemical or radiation, and when symptoms and signs are first apparent...
. The virus is shed for one to three weeks postinfection. Latently infected cats (carriers) will shed FHV-1 intermittently for life, with the virus persisting within the trigeminal ganglion. Stress and use of 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 precipitate shedding
Viral shedding
Viral shedding refers to the successful reproduction, expulsion, and host-cell infection caused by virus progeny. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell by several methods.The term is used...
. Most disinfectants, antiseptics and detergents are effective against the virus.
Clinical Signs
Conjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...
, and sometimes fever (up to 106) and loss of appetite. These usually resolve within four to seven days, but secondary bacterial infections can cause the persistence of clinical signs for weeks. Frontal sinusitis
Sinusitis
Sinusitis is inflammation of the paranasal sinuses, which may be due to infection, allergy, or autoimmune issues. Most cases are due to a viral infection and resolve over the course of 10 days...
and empyema
Empyema
Pleural empyema is an accumulation of pus in the pleural cavity. Most pleural empyemas arise from an infection within the lung , often associated with parapneumonic effusions. There are three stages: exudative, fibrinopurulent and organizing. In the exudative stage, the pus accumulates...
can also result.
FHV-1 also has a predilection for cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
l epithelium, resulting in corneal ulcers, often pinpoint or dendritic
Dendrite
Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or soma, of the neuron from which the dendrites project...
in shape. Other ocular signs of FHV-1 infection include conjunctivitis
Conjunctivitis
Conjunctivitis refers to inflammation of the conjunctiva...
, keratitis
Keratitis
Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.-Types:...
, keratoconjunctivitis sicca
Keratoconjunctivitis sicca
Keratoconjunctivitis sicca , also called keratitis sicca, xerophthalmia or dry eye syndrome is an eye disease caused by eye dryness, which, in turn, is caused by either decreased tear production or increased tear film evaporation. It is found in humans and some animals...
(decreased tear production), and corneal sequestra. Infection of the nasolacrimal duct
Nasolacrimal duct
The nasolacrimal duct carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which drains into the inferior nasal meatus...
can result in chronic epiphora
Epiphora (medical)
Epiphora is overflow of tears onto the face. A clinical sign or condition that constitutes insufficient tear film drainage from the eyes in that tears will drain down the face rather than through the nasolacrimal system.-Etiology:...
(excess tearing). Ulcerative skin disease can also result from FHV-1 infection. FHV-1 can also cause abortion in pregnant queens, usually at the sixth week of gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
, although this may be due to systemic effects of the infection rather than the virus directly.
In chronic nasal and sinus disease of cats, FHV-1 may play more of an initiating role than an ongoing cause. Infection at an early age may permanently damage nasal and sinus tissue, causing a disruption of cilia
Cilium
A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the much larger cell body....
ry clearance of mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
and bacteria, and predispose these cats to chronic bacterial infections.
Diagnosis
Diagnosis of FVR is usually by clinical signs, especially corneal ulceration. Definitive diagnosis can be done by direct immunofluorescenceImmunofluorescence
Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on biological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, and therefore allows...
or virus isolation. However, many healthy cats are subclinical carriers of feline herpes virus, so a positive test for FHV-1 does not necessarily indicate that signs of an upper respiratory tract infection are due to FVR. Early in the course of the disease, histological
Histology
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...
analysis of cells from the tonsils, nasal tissue, or nictitating membrane
Nictitating membrane
The nictitating membrane is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have a full nictitating membrane; in many mammals, there is a small...
(third eyelid) may show inclusion bodies
Inclusion bodies
Inclusion bodies are nuclear or cytoplasmic aggregates of stainable substances, usually proteins. They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins...
(a collection of viral particles) within the nucleus
Cell nucleus
In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these...
of infected cells.
Treatment and prevention
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 commonly used to prevent secondary bacterial infection. There are no specific antiviral drug
Antiviral drug
Antiviral drugs are a class of medication used specifically for treating viral infections. Like antibiotics for bacteria, specific antivirals are used for specific viruses...
s in common use at this time for FVR, although one study has shown that ganciclovir
Ganciclovir
Ganciclovir INN is an antiviral medication used to treat or prevent cytomegalovirus infections.Ganciclovir sodium is marketed under the trade names Cytovene and Cymevene . Ganciclovir for ocular use is marketed under the trade name Vitrasert...
, PMEDAP, and cidofovir
Cidofovir
Cidofovir is an injectable antiviral medication for the treatment of cytomegalovirus retinitis in patients with AIDS. It suppresses CMV replication by selective inhibition of viral DNA polymerase and therefore prevention of viral replication and transcription...
hold promise for treatment. More recent research has indicated that systemic famciclovir is effective at treating this infection in cats without the side effects reported with other anti-viral agents. More severe cases may require supportive care such as intravenous fluid therapy
Intravenous therapy
Intravenous therapy or IV therapy is the infusion of liquid substances directly into a vein. The word intravenous simply means "within a vein". Therapies administered intravenously are often called specialty pharmaceuticals...
, oxygen therapy
Oxygen therapy
Oxygen therapy is the administration of oxygen as a medical intervention, which can be for a variety of purposes in both chronic and acute patient care...
, or even a feeding tube
Feeding tube
A feeding tube is a medical device used to provide nutrition to patients who cannot obtain nutrition by swallowing. The state of being fed by a feeding tube is called gavage, enteral feeding or tube feeding...
. Conjunctivitis and corneal ulcers are treated with topical antibiotics for secondary bacterial infection. L-lysine
Lysine
Lysine is an α-amino acid with the chemical formula HO2CCH4NH2. It is an essential amino acid, which means that the human body cannot synthesize it. Its codons are AAA and AAG....
has been recommended anecdotally to suppress viral replication. A more recent study supports the use of L-lysine for treatment of ocular signs of FHV-1 infection.
There is a vaccine
Vaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
for FHV-1 available (ATCvet code: , plus various combination vaccines), but although it limits the severity of the disease and may reduce viral shedding
Viral shedding
Viral shedding refers to the successful reproduction, expulsion, and host-cell infection caused by virus progeny. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruses may begin to leave the cell by several methods.The term is used...
, it does not prevent infection with FVR. Studies have shown a duration of immunity of this vaccine to be at least three years. The use of serology
Serology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...
to demonstrate circulating antibodies
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
to FHV-1 has been shown to have a positive predictive value for indicating protection from this disease. Most household disinfectants
Disinfection
Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially nonresistant bacterial spores; it is less effective than sterilisation, which is an extreme physical...
will inactivate FHV-1. The virus can survive up to 18 hours in a damp environment, but less in a dry environment and only shortly as an aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
.