| Feline herpesvirus | |
|---|---|
Virus classification | |
| (unranked): | Virus |
| Realm: | Duplodnaviria |
| Kingdom: | Heunggongvirae |
| Phylum: | Peploviricota |
| Class: | Herviviricetes |
| Order: | Herpesvirales |
| Family: | Orthoherpesviridae |
| Genus: | Varicellovirus |
| Species: | Varicellovirus felidalpha1 |
| Synonyms[2] | |
| |
Feline viral rhinotracheitis (FVR) is an upper respiratory or pulmonary infection ofcats caused byFeline herpesvirus, also calledFeline herpesvirus 1 (FeHV-1), of the familyHerpesviridae. It is also commonly referred to asfeline influenza,feline coryza, andfeline pneumonia but, as these terms describe other very distinct collections of respiratory symptoms, they are misnomers for the condition.Viral respiratory diseases in cats can be serious, especially incatteries andkennels. Causing one-half of the respiratory diseases in cats,[3] FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease isfeline calicivirus.
FVR is very contagious and can cause severe disease, including death frompneumonia in young kittens. It may causeflat-chested kitten syndrome, but most evidence for this is anecdotal. All members of the familyFelidae are susceptible to FVR; in fact, FHV-1 has caused a fatalencephalitis inlions inGermany.[4]
FHV-1 was first isolated from cats in 1958 in theUnited States.[5]
FVR is transmitted through direct contact only.[6] It replicates in the nasal andnasopharyngeal tissues and thetonsils.Viremia (the presence of the virus in the blood) is rare. Thevirus is shed in saliva and eye and nasal secretions, and can also be spread byfomites. FVR has a two- to five-dayincubation period.[3] The virus is shed for one to three weeks postinfection.[4] Latently infected cats (carriers) will shed FHV-1 intermittently for life, with the virus persisting within thetrigeminal ganglion. Stress and use ofcorticosteroids precipitateshedding. Most disinfectants, antiseptics and detergents are effective against the virus.[6]
Initial signs of FVR includecoughing,sneezing, nasal discharge,conjunctivitis, and sometimes fever (up to 106 °F (41 °C)) 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.[4] Frontalsinusitis andempyema can also result.
FHV-1 also has a predilection forcorneal epithelium, resulting incorneal ulcers, often pinpoint ordendritic in shape. Other ocular signs of FHV-1 infection include conjunctivitis,keratitis,keratoconjunctivitis sicca (decreased tear production), andcorneal sequestra.[7] Infection of thenasolacrimal duct can result in chronicepiphora (excess tearing). Ulcerative skin disease can also result from FHV-1 infection.[8] FHV-1 can also cause abortion in pregnant queens, usually at the sixth week ofgestation,[3] 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 ofciliary clearance ofmucus and bacteria, and predispose these cats to chronic bacterial infections.[9]
Diagnosis of FVR is usually by clinical signs, especially corneal ulceration. Definitive diagnosis can be done by directimmunofluorescence orvirus 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 analysis of cells from the tonsils, nasal tissue, ornictitating membrane (third eyelid) may showinclusion bodies (a collection of viral particles) within thenucleus of infected cells.[10]
Polyprenyl immunostimulant is the only currently-approved treatment in the US for feline rhinotracheitis caused by herpesvirus.[11] Effectiveness was demonstrated in a clinical study with cats experimentally infected with feline herpesvirus: 20 cats were treated with polyprenyl immunostimulant and 20 received a placebo. The study established that the severity of the disease was lower in the group treated with polyprenyl.[12] Safety was demonstrated in 390 personally-owned cats from 2 days to 16 years of age, residing in 10 states.[12]
Antibiotics are commonly used to prevent secondary bacterial infection. There are no specificantiviral drugs in common use at this time for FVR, although one study has shown thatganciclovir,PMEDAP, andcidofovir hold promise for treatment.[13] More recent research has indicated that systemicfamciclovir is effective at treating this infection in cats without the side effects reported with other anti-viral agents.[14] More severe cases may require supportive care such asintravenous fluid therapy,oxygen therapy, or even afeeding tube. Conjunctivitis and corneal ulcers are treated with topical antibiotics for secondary bacterial infection.Lysine is commonly used as a treatment; however, in a 2015systematic review, the authors investigated all clinical trials with cats as well asin vitro studies and concluded that lysine supplementation is likely not effective for the treatment or prevention of feline herpesvirus 1 infection.[15]
There is avaccine for FHV-1 available (ATCvet code:QI06AA08 (WHO), plus various combination vaccines), but although it limits or weakens the severity of theviral shedding, it does not prevent infection with FVR.[16] Studies have shown a duration of immunity of this vaccine to be at least three years.[17] The use ofserology to demonstrate circulatingantibodies to FHV-1 has been shown to have a positive predictive value for indicating protection from this disease.[18] The combination vaccine, Purevax RC, against feline viral rhinotracheitis and feline calicivirus was authorised for medical use in the European Union in February 2005.[19][20]
Most householddisinfectants 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 anaerosol.[16]
Felid herpesvirus 1 Felid herpesvirus 1 [FJ478159=NC_013590] (FeHV-1) (Feline rhinotracheitis virus)
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