Herpes Virus Feline – A Research Case Study
Herpes feline (FHV, FHV-1) is a highly contagious virus, a primary factor for high respiratory (URI) or cat influenza infections in cats.
The virus is omnipresent and causes cats worldwide to get sick. See also Higher respiratory (URI, Cat Flu) infections in cats. The overwhelming majority of URI in cats are caused by FHV and feline caliciviruses together.
How Does The FHV Spread?
The feline herpesvirus (FHV) is a virus that mainly causes acute ULIs in cats, although some other disorders have also been associated with it (see below). The virus is easily spread across cats:
Direct contact – through saliva, eye, or nasal secretions.
Snow droplet inhalation.
Bowls and litter trays sharing or food.
A contaminated environment (including bedding and toilets) – with FHV is of less significance than FCV since it is probably only 1–2 days in the environment for the virus to survive.
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Almost all cats will be latent with FHV after infection (the virus persists in nerve cells). Infected cats thus become carriers of the virus for a lifetime. This does not cause problems in many cats and is not a danger to others, so they continue to shed viruses. But some cats repeat the virus on an intermittent basis and this is more prevalent after stress episodes or when the immune system is suppressed (eg, following the use of corticosteroids). Some cats also develop a mild recrudescence of clinical signs when a virus is removed again. Persistent FHV infection may also cause eye problems (see below).
What Are The Clinical Signs Of FHV?
Acute URI is the most common manifestation of FHV infection. A high respiratory infection. Signs typical are conjunctivitis, eye flux, sneezing, nasal release, salivation, pharyngitis, lethargy, inappetence, fever, and coughing sometimes. Signs may last between a few days and weeks and virus shedding usually lasts for about three weeks. In general, FHV clinical diseases are more severe than FCV.
Keratitis – though still fairly rare, conjunctivitis and keratitis (infection and cornea inflammation – the clear frontal portion of the eye) are one manifestation of chronic (long-term) FHV infection seen in many cats. Although keratitis can be caused by a variety of factors, FHV infection creates several small branching corneal ulcers (known as “dendritic keratitis”), which is considered diagnostic of FHV infection.
FHV-related dermatitis – the development of skin inflammation and ulceration is a rare manifestation of chronic (long-term) FHV infection. This is usually seen around the nose and mouth, but other areas like the front legs may be affected. Only seldom is this seen?
What Is The Diagnosis Of FHV Infection?
In most cases, there is no need for a certain diagnosis of FHV infection. A presumed diagnosis of FHV (and/or feline calicivirus – FCV) infection is sufficient for the presence of typical URI signals.
In a veterinary laboratory where the virus is cultured or mostly detected by the PCR, eyepiece or oral swabs can be submitted when a specific diagnosis is required (a molecular technique for detecting the genetic material of the virus). Virus evidence may also occur in biopsy and may be useful for FHV-related dermatitis diagnosis (skin infection).
FHV Infection Treatment and Management
Secondary bacterial infections are common in FHV infections, necessitating antibiotic treatment. In serious cases, cats may need to be admitted to the hospital for intravenous hydration therapy and nutritional support. In cases of severe nasal congestion, steam inhalation or nebulization may aid, and because the cat won’t be able to smell properly, using canned or sachet foods that have been gently warmed will help.
Unlike with FCV, antiviral medications are available for FHV infection and can be very useful in controlling the disease’s clinical symptoms.
Famciclovir, a human anti-herpes virus medicine that has been found to be safe and effective in cats, is a systemic antiviral therapy. It can be taken by mouth and is particularly useful in the treatment of severe acute infections.
Idoxuridine, trifluridine, and cidofovir are all human anti-herpes virus medicines that can be used successfully as topical ocular (eye drop) therapy for FHV-associated conjunctivitis and keratitis. Some of these medications must be administered often (many times per day), and they may be coupled with topical interferon to improve efficacy.
In cats, every cat with clinical signs, if possible, must be isolated and strict hygiene must be ensured by the use of individual food bowls, litter trays, hand-washing tools, separate (or disposable) plaster, etc.
The FHV Vaccination
For all cats, FHV vaccination is important. In kittens, two or three injections beginning at around eight weeks of age are recommended. At age one, cats should be given a booster and afterward, further booster vaccines should be provided every 1-3 years.
Vaccination will not necessarily prevent FHV infection but significantly reduce clinical disease severity. Unlike FCV, only one FHV strain is effective so the existence of different strains does not complicate vaccination.
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