When virus is shed again, some cats will also develop mild recrudescence of clinical signs. Additionally, persistent FHV infection can cause ocular problems see below. In most cases, a specific diagnosis of FHV infection will not be required. If a specific diagnosis is required, ocular or oral swabs can be submitted to a veterinary laboratory where the virus can be grown in culture or, more commonly, detected by PCR a molecular technique for detecting the genetic material of the virus.
Evidence of the virus may also be present in biopsies and can be useful for the diagnosis of FHV-associated dermatitis skin infection.
FHV infections are frequently complicated by secondary bacterial infections, so supportive treatment with antibiotics is usually required. Good nursing care is critical and cats may need to be hospitalised for intravenous fluid therapy and nutritional support in severe cases.
Steam inhalation or nebulisation may help in cases of severe nasal congestion and as the cat will not be able to smell food well, using tinned or sachet foods that are gently warmed will help.
Unlike FCV, with FHV infection certain anti-viral drugs are available and can be very helpful in managing the clinical manifestations of disease. In colonies of cats, any cat showing clinical signs should be isolated if at all possible, and strict hygiene should be ensured with disinfection, and use of separate feeding bowls, litter trays, implements etc, careful washing of hands, use of separate or disposable apron etc.
Vaccination for FHV is important for all cats. Two or three injections are recommended in kittens, starting at around 8 weeks of age. Cats should receive a booster at a year of age, and after that should receive further booster vaccines every 1—3 years. Vaccination does not necessarily prevent infection with FHV but will greatly reduce the severity of clinical disease.
Unlike FCV, there is effectively only one strain of FHV, so vaccination is not complicated by the existence of different strains. All our advice is freely accessible to everyone, wherever you are in the world.
However, as a charity, we need your support to enable us to keep delivering high quality and up to date information for everyone. Therefore survival rates among affected cats are expected to be high presuming antibacterial, hydration, and nutritional support can be provided. In multiple-cat households the problem of acute viral URD in kittens does not stop despite successful management of individual cat infections, implementation of a comprehensive vaccination program, and a seropositive adult population.
One-hundred percent of kittens that recover from acute FHV-1 infection are expected to become chronic carrier cats. Healthy appearing carriers maintained in the population serve as reservoirs and can spread virulent virus to susceptible kittens, as well as adult cats , through direct cat-to-cat contact or fomite contamination.
Therefore, the persistence of viral URD within a population depends on the ability of these viruses to sustain themselves in adult carrier cats.
FCV carrier cats, therefore, pose a substantial threat to susceptible kittens in multiple-cat population. On the other hand, the FHV-1 carrier cats have a truly latent infection.
Viral shedding is not continuous, but can occur subsequent to physiological stress e. Although the virus is consistently recovered from tonsils of affected carriers, tonsillectomy does not eliminate virus excretion. Obviously, other sites of persistence in the oropharynx must exist.
The occurrence of repeat outbreaks of feline viral upper respiratory disease within a multiple cat household, particularly when kitten morbidity is high, supports the hypothesis that one or more chronic carrier cats live within the population. Diagnosis of the chronic carrier cat can be quite difficult even when virus isolation is attempted.
Clinical signs in affected cats are variable to nonexistent. When present, however, they may provide important clues regarding the presence of a chronic carrier within a given population.
Characteristically, the sneezing and nasal discharge respond, usually completely, to empiric antibiotic treatment. However, resolution of clinical signs is only effective during the time of treatment. Within 3 days following discontinuation of the antibiotic, clinical signs typically re-occur. In addition to paroxysmal sneezing and nasal discharge, stomatitis, chronic gingivitis, gingival ulceration, and periodontal disease with premature loss of teeth will be evident. Radiographs may reveal secondary frontal sinusitis.
Recrudescent FHV-1 infections in adult cats manifest in a variety of ways: herpesvirus keratitis, corneal ulceration, and symblepharon in severe cases. Sneezing and nasal discharge is relatively uncommon. The author has proposed that feline vestibular syndrome is, in fact, yet another manifestation of feline herpesvirus-1 recrudescence. Unfortunately, even the most comprehensive vaccination program will not guarantee protection against persistent virus infections occurring within a household.
Objectively, management of chronic feline viral URD within a household or cattery, must be directed at effective control: strategic vaccination programs, strict environmental regulation, minimizing exposure, and, when possible, identification and isolation of carrier cats. Although parenterally vaccinated cats do develop significant, sometimes referred to as "protective," circulating antibody levels, immune carrier cats are commonplace.
Use of intranasal vaccination, if available, has been shown to mitigate the risk of outbreaks within a closed household and for reducing kitten losses associated with enzootic viral URD. Several drugs have been used in an attempt to manage clinical signs of chronic, intermittent upper respiratory disease attributed to a chronic FCV or FHV-1 carrier state. For example, any broad spectrum antibiotic will control the clinical signs but, as described above, the response is typically limited to the time the cat is receiving the drug.
Amoxicillin-clavulanate, metronidazole, and doxycycline have been recommended. Immunomodulation has been attempted using human recombinant interferon 30 I. In our experience, little to no discernable response has been detected. A new recombinant feline-origin omega interferon Virbagen Omega is being studied at this time Administration of l-lysine a non-prescription amino acid available in 'health food stores' , mg administered orally, with food, once daily, for an indefinite period, has been recommended to prevent the consequences of viral recrudescence in FHV-1 carrier cats.
Veterinary clinics should be closed to new feline patients until the outbreak is under control. Recovered cats will shed virus for weeks to months, although they may not be contagious to in-contact cats. Feline herpesvirus-1 belongs to the Varicellovirus genus of the Herpesviridae family and is an alphaherpesvirus. The herpesvirus family is a large and diverse group of enveloped DNA viruses that infect humans and animals. They are noted for their ability to produce latent infections, particularly in neural cells.
FHV isolates worldwide belong to a single serotype. Isolates have recently been divided into four groups based on genetic analysis, although the relationship between the classifications and variations in virulence is unknown. As an enveloped virus, FHV is very fragile in the environment, surviving only about 18 hours under moist conditions. It is also highly susceptible to most common disinfectants. FHV is shed in secretions from the oropharynx, conjunctiva and nose.
As for FCV, transmission is mainly from direct contact and via fomites. In latency, the virus persists in a nonreplicating state in various tissues, such as the trigeminal ganglion, optic nerves, cornea, tonsils, etc. Reactivation of shedding commonly occurs after a stressor e. FHV shedding starts days after the stressor, and lasts up to 2 weeks.
FHV is commonly associated with corneal ulceration and keratitis. Dendritic ulcers are generally considered pathognomonic for FHV infection. FHV has also been associated with other ocular diseases, including anterior uveitis, corneal sequestration, and eosinophilic keratitis. Severe pharyngitis may be seen as the only clinical sign in some cats infected with FHV. As for FCV, treatment is primarily supportive and symptomatic. However, a few specific antiviral drugs, both topical and oral, have been used in treatment of FHV.
Nucleoside analogs selectively inhibit replication of herpesviruses by interfering with DNA synthesis. Topical antivirals include trifluridine and idoxuridine. Other topical antivirals, such as 0. Oral antiviral drugs are often associated with unacceptable adverse effects in cats. Famciclovir, the prodrug for penciclovir, has been recommended for patients with severe clinical signs Some data on pharmacokinetics has been published, but information on safety and efficacy are only anecdotal.
Lysine is an amino acid that antagonizes the availability of arginine, an essential amino acid for viral protein synthesis. Oral administration of large doses of lysine to cats appears to be safe and can reduce the severity of conjunctivitis in primary FHV infections as well as reduce ocular viral shedding. Lactoferrin is an iron-binding protein found in milk and in neutrophil granules with antimicrobial and immunomodulating effects. Bovine lactoferrin has been shown to inhibit FHV replication in vitro by preventing viral adsorption to the cell surface.
Clinical trials of topical lactoferrin for FHV keratitis have not been reported. Interferons have diverse immunological and antiviral functions. Human recombinant interferon-alpha has been shown to be effective against FHV in cell culture and has been associated with reduced clinical disease but not FHV shedding when used at low daily oral doses.
Investigation into stability of diluted interferon solutions and the best dispensing methods is needed. Controlled trials are needed to determine the efficacy of interferons in cats with recrudescent infections. Ulcerative and crusting facial and nasal dermatitis associated with FHV has been called an emerging dermatosis in the cat but case reports in the literature date to the s. FHV has also been implicated as a cause of facial ulcers in cheetahs. Persistent lesions, often resembling eosinophilic granulomas or allergic dermatitis, are most typically found on the nose, but also on haired areas of the face.
Other skin diseases that may be confused with FHV ulcerative dermatitis include bacterial dermatitis and dermatophytosis. Patients with this manifestation of FHV infection may have immunosuppression from administration of corticosteroids, stressors such as overcrowding, or concurrent diseases such as retrovirus infection. Affected cats may have a history of upper respiratory tract disease.
Histopathology reveals a marked ulcerative eosinophilic infiltrate. Intranuclear viral inclusion bodies in the epithelium may be overlooked by pathologists. Treatment recommendations include human recombinant interferon-alpha doses ranging from IU daily PO to 1.
The most reliable assay is virus isolation using oropharyngeal also nasal and conjunctival swabs. Careful sampling and handling of swabs is necessary, particularly for FHV as it is more fragile. Proper transport media and submission procedures should be followed as recommended by the diagnostic laboratory. Fluorescent antibody testing of cytology slides can be associated with false-positive results due to nonspecific background fluorescence and application of fluorescein to the eye before sampling.
PCR technology is rapid, sensitive and becoming widely available. However, test sensitivity varies greatly from lab to lab, depending on the specific technique employed as well as other factors. PCR may be particularly useful for detection of FHV in vaccinated cats, or during recrudescence of clinical signs. False positive results can be obtained with PCR if samples are contaminated during collection or during analysis.
Interpretation of test results should always be made in the context of the patient, for both FCV and FHV can be isolated from many cats without clinical signs. Negative test results can be obtained in truly infected cats for a variety of reasons. Janet Foley at the University of California, Davis jefoley ucdavis. Vaccination can, however, reduce the severity of disease and shorten the duration of shedding. The best protection may be from modified live virus vaccines. Intranasal vaccines provide rapid immunity, even in the face of maternal antibodies, and can be useful for control of outbreaks in multi-cat environments such as shelters and catteries.
Currently available FCV vaccines do not provide broad cross protection against field isolates. Several authorities have proposed incorporating more field strains into vaccines. Practitioners should carefully evaluate which patients are actually at risk of VS-FCV before administering the vaccine, especially since it is an adjuvanted product. Beaumont, S. Maggs, et al. Effects of bovine lactoferrin on in vitro replication of feline herpesvirus.
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