[BLOG] Feline upper respiratory diseases: 24 things you need to know concerning Feline Herpes Virus (aka FHV-1)

Each time I visit one of our shelter partner, we obviously spend some time discussing the challenges they face on a daily basis. Obviously, infectious diseases are big. Obviously, feline upper respiratory diseases are one of these. If you remember our previous post on this topic, it’s in fact a syndrome: an association of clinical signs that can be cause by different pathogens, acting alone or as a group. Today, let’s focus on one of these bad guys: the feline herpes-virus, aka FHV-1.

Fact #1: FHV-1 is an alpha-herpesvirus of cats. There is only one serotype (=a strain that can be be distinguished by serology) occurring worldwide. Different isolates exist, but they vary very little in their composition or in the signs that they produce.

Fact #2: FHV-1 is specific to the feline species. It has no zoonotic potential and cannot therefore contaminate humans.

Fact #3: Among clinically infected cats, prevalence rates for FHV-1 have ranged from 11% to 39%. This is one of the most common causes of feline upper respiratory tract disease.

Fact #4: Among cats without clinical signs, shedding rates of 0.4 to 1.75% have been reported. This means that cats might not exhibit ANY clinical signs, but still shed the virus and contaminate others.

Fact #5: The viruses are mainly shed in ocular, nasal and oral secretions and spread is largely by contact with an infected cat.

Fact #6: FHV-1 is relatively fragile outside the host and is highly susceptible to the effect of common disinfectant.

Fact #7: In some situations, particularly within a cattery, indirect transmission may also occur. Indeed, these viruses can survive 18 hours at 15ºC in a damp environment and up to 12 hours in a dry environment.

Fact #8: Cats do not appear to be able to produce an infectious aerosol for these agents during normal respiration

Fact #9: However, sneezing cats may propel viral-bearing macrodroplets up to 1 to 2m. Droplet transmission is probably important in shelters with group-housing where cats can sneeze in close proximity to one another

Fact #10: In shelters with facing cage banks, a distance of more than 2m is required to prevent droplet transmission.

Fact #11: Contaminated secretions may be present on cages, on feeding and cleaning ustensils and on personnel. Proper sanitation/hygiene is paramount.

Fact #12: 80-100% recovered cats become latently infected carriers. When a cat is infected, it is generally infected for life.

Fact #13: Viral reactivation is more likely after stress (for example going into a boarding or rescue). Once reactivation occurs, depending on factor such as hygiene precautions infection can spread rapidly, especially in shelter environments.

Fact #14: The stress of parturition and lactation can also precipitate viral shedding

Fact #15: Shedding does not occur immediately after the stress; a lag period of approximately 1 week occurs, followed by a shedding episode of from 1 to 2 weeks.

Fact #16: Viral shedding can be detected as early as 24 hours after infection and generally persists 1-3 weeks.

Fact #17: Viral replication is normally restricted to areas of lower body temperature, such as the respiratory tract. That’s why FHV-1 generally causes a severe upper respiratory disease.

Fact #18: Generalized disease can however be seen in debilitated animals or in neonatal kittens less than 3 weeks of age since they cannot thermoregulate.

Fact #19: Early signs include depression, marked sneezing, inappetence and pyrexia followed rapidly by serous ocular and nasal discharge. These initial clinical signs may be accompanied by excessive salivation with drooling. Conjunctivitis and eventually herpetic ocular ulcers typically develops. Oral ulcerations can occur but are rare.

Fact #20: Mortality with FHV-1 is generally low, except in very young kittens or immunosuppressed cats because of the generalized disease.

Fact #21: Abortion can be observed in pregnant queens but is most likely due to the severe systemic effects of the illness rather than a direct effect of the virus itself.

Fact #22: In most cases, antibacterial treatment may not be required. Good nursing care is essential.

Fact #23: Many cats will eat less because of an impaired sense of smell or ulcers in the oral cavity, and thus they should be encouraged to eat by offering highly palatable diets. Nasal discharge should be wiped away with saline.

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