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Virology > Feline Herpes and Calicivirus > Flashcards

Feline Herpes and Calicivirus Flashcards

1
Q

What is the structure of of Feline Herpes Virus-1 (FHV-1)? How sturdy as

A
  • Enveloped, double-stranded (ds)-DNA virus
  • Relatively fragile and can survive for up to 18h in a damp environment, less in dry conditions
  • Highly susceptible to common disinfectants
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2
Q

How many serotypes are there for FHV?

A

1, field strains are relatively homogenous

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3
Q

What causes the majority of URIs in cats?

A
  • FHV-1
  • Feline calicivirus
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4
Q

What age do cats normally get FHV-1?

A
  • Most infected between 8-12 weeks old
  • Primary infection CAN occur in older kittens and adults
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5
Q

What anatomical structures does FHV-1 infect

A
  • Nasal mucosal lining (& nasal turbinates)
  • Tonsil/pharyngeal
  • Conjunctiva
  • Cornea
  • Rarely, epidermis, mainly on the face
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6
Q

What are the clinical signs of a FHV-1 infection

A
  • URI
  • ocular disease
  • rarely - facial dermatitis
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7
Q

How is FHV-1 shed?

A
  • ocular/nasal secretions
  • saliva
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8
Q

What is the incubation period for FHV-1?

A

2-5 days

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9
Q

How long does a FHV-1 infection last?

A
  • Clinical signs usually resolve in 2 - 3 weeks
    • some develop chronic diseases
  • Secondary bacterial disease may occur
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10
Q

What symptoms are common with conjunctivitis?

A
  • Hyperemia
  • Chemosis
  • Epiphora
  • blepharospasm
  • bacterial co-infection may occur
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11
Q

What is the concern with corneal ulcers?

A
  • superficial corneal ulcer can progress to:
    • stromal corneal ulcer
    • descemetocele
    • perforation
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12
Q

What is the hallmark of FHV-1?

A
  • Ability to establish latent infection
    • Virus lies dormant within a cell following acute disease
  • Pathogenesis:
    • Acute primary infection of alpha-herpesvirus ⇢ latency (sensory nerve ⇢ trigeminal nerve ganglion) ⇢ Reactivation (stress/spontaneous)
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13
Q

How common are latent FHV-1 infections?

A
  • 82% of infected cats
  • Not all experience virus reactivation
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14
Q

What can reactivate a FHV-1 infection?

A
  • Stressful conditions or steroid adminiastration
    • steroid: 69% shedding in 2-7 days
    • Rehousing: 18% shedding
    • Spontaneous 29% within 8 months (stressor unknown)
  • Stressors:
    • corticosteroid
    • co-infection
    • parturition/lactation
    • change of housing, etc
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15
Q

What is the major source of environmental contamination with FHV-1

A
  • Acutely infected cats (primary infection)
  • Latently infected cats experiencing reactivation
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16
Q

What impacts does chronic FHV-1 cause?

A
  • Scarring of nasal turbinates from FHV-1 (or FCV) and secondary bacterial infection ⇢ chronic rhinitis
  • Scarring of ocular tissue ⇢ chronic ocular disease
17
Q

How is FHV-1 transmitted? what contributes to its contagiousness?

A
  • Direct contact
    • Bodily fluids > aerosol
  • Relatively fragile outside the host, but HIGHLY contagious
  • Young cats predisposed (maternal immunity wanes)
  • Majority of cats are chronic shedders (weeks or longer) even after clinical signs have resolved
    • majority become latently infectant and can have recurrent disease
  • Short immunity - reinfection can occur
18
Q

How is FHV-1 diagnosed?

A
  • Usually based on hx and clinical signs
    • young kitten showing URI and ocular signs
    • rapidly spread among cats
  • Diagnostics: for severe or chronic cases
    • Virus detection by isolation or PCR
      • Ocular, nasal, and/or oropharyngeal swabs
    • Positive can be incidental - virus reactivation without clinical signs, recently vaccinated cats
    • False negative: intermittent virus shedding, inadequate handling of samples, lab errors, etc
  • presence of virus and clinical signs are poorly correlated
    • use caution when interpreting diagnostic tests
19
Q

What is the FHV-1 vaccination? What effects does it have?

A
  • Core vaccine (Feline panleukopenia, FHV-1, FCV, rabies, and FeLV)
  • Attenuated live (+/- adjuvanted) and inactivated vaccines given parentally
  • Attenuated live intranasal vaccine: faster onset of protection within 4 - 6 days
  • Vaccinations can decrease virus shedding and clinical signs but does not necessarily prevent infection, latency or reactivation
  • Relatively efficacious to all field strains but disease still can occur due to inadequate vaccination, high virus challenge dose, immunocompetence status, etc
  • Prevention and control of FHV-1 requires vaccination + management
20
Q

How is a FHV-1 infection treated?

A
  • Self-limiting - Supportive therapy
  • Severe signs may require antiviral drug treatment
    • No licensed antiviral dugs specifically for FHV-1
    • Human herpes antiviral drugs for oral use (nucleoside analogues - ie famciclovir) - controlled studies required
    • Ophthalmic herpes antiviral dug for humans (cidofovir, trifluridine, idoxuridine, vidarabine) Efficacy is not well known
  • L-lysine- thought to compete with arginine, an AA essential for FHV-1 replication, however conflicting reports on the effectiveness. May increase disease severity and viral shedding
21
Q

What is the Family and Genus of Feline Calicivirus?

A
  • Family Caliciviridae
  • Genus vesivirus
22
Q

What is the structure of FCV?

A
    • sense ssRNA virus
  • Non-enveloped
  • 38nm particle
23
Q

How many serotypes of FCV are there?

A
  • One serotype
    • diverse field strains w/ varying antigenicity and pathogenicity
24
Q

How stable is FCV?

A
  • Can survive for weeks - months in dry conditions
    • up to 1 month on dry surface at room temperature and longer in colder conditions
  • Resistant to many commonly used disinfectants
    • Effective: 5% bleach (1:32 dilution) peroxygen compounds, glutaraldehydes
    • NOT: quaternary ammonium
25
Q

How is FCV transmitted?

A
  • Direct contact and fomites - primary
  • Highly contagious
  • Most cats are chronic shedders for ~30 days +
    • some shed for months - years w/out clinical sings
  • Short immunity - reinfection can occur
26
Q

What are the types of FCV infections?

A
  • Upper respiratory signs/oral lesions
    • High morbidity, low mortality
    • Very common
  • Systemic, virulent FCV infection
    • High morbidity, high mortality
    • very rare
27
Q

What is the incubation time for URI calicivirus?

A

2-10 days

28
Q

What are the clinical signs of FCV infection?

A
  • Fever
  • Lethargy
  • Any of:
    • Upper respiratory signs: conjunctivitis and rhinitis, usually milder, but can be as severe as FHV-1
    • Oral vesicles and ulceration - gums, tongue, palate, lips, nasal philtrum - hypersalivation
    • Dermatitis - skin and nasal ulceration
    • Acute arthritis: transient lameness is associated with some FCV strains
      • occurs a few days of weeks after the acute oral/respiratory signs
29
Q

What is Lymphoplasmacytic stomatitis?

A
  • Different form stomatitis caused by calicivirus
  • Aka: chronic plasma cell gingivitis and pharyngitis, plasma cell stomatitis, chronic ulceroproliferative faucitis
  • Chronic inflammatory disease:
    • chronic ulceroproliferative lesion around the oral fauces or the oral cavity leading to the pharynx
      • Lesion densely infiltrated with plasma cells and lymphocytes
  • Cause unknown
    • atypical and persistent immune response towards viral, bacterial, or environmental antigen is implicated
30
Q

How is FCV diagnosed?

A
  • Based on hx and clinical sings
  • Dx test: Virus isolation or RT-PCR form oral/nasal secretion swab samples
    • May be useful to identify FCV as a cause for URI in shelters because FCV can persist in the environment
  • Presence of virus and clinical signs are poorly correlated - use caution when interpreting dx tests
31
Q

How is FCV infection treated?

A
  • Self-limiting = supportive care for severe cats
  • No antiviral drugs
32
Q

What type of vaccine in the FCV vaccine? What affects does it have?

A
  • Core vaccine
  • Attenuated or inactivated vaccines given parentally
  • Intranasal attenuated live vaccine
  • One FCV serotype but high antigenic variability among field isolates
    • Vaccine does NOT protect equally against all strains
  • Can decrease virus shedding and clinical signs buts does not necessarily prevent infection or chronic carrier status
33
Q

What is the Virulent systemic calicivirus infection (vs-FCV)?

A
  • Reported in the US and EU since 1998
  • High fatality rate up to 67%
  • Incubation period 1-5 days
  • Rare
    • Almost exclusively outbreaks occur in shelters, rescues or catteries
    • not a disease of household cats
34
Q

When should Vs-FCV be suspected?

A
  • Hx: recent exposure to a multi-cat environment or recent addition of a cat; more than one cat affected; fully vaccinated, otherwise healthy adult cats affected
  • General signs of FCV followed by severe systemic signs:
    • Death in some cats
    • Signs of vasculitis (facial edema and limbs) not explained by other causes
    • Liver necrosis on biopsy or necropsy
    • More severe in adults than kittens
35
Q

How is Vs-FCV diagnosed?

A
  • Serology and virus detection in nasal, conjunctival or oropharyngeal swabs have limited use because:
    • No genetic markers for vs-FCV
    • FCV infection is widespread
  • Necropsy - rule out other causes
  • Gold Standard: IHC on internal organs
36
Q

How is a vs-FCV infection managed?

A
  • Outpatient treatment if possible - avoid viral transmission in clinics
  • Strict isolation if hospitalized
  • Thorough cleansing of environment/clothing/equipment
  • No new cats into the environment until the outbreak is under control
  • Recovered cats may shed the viruses for months
37
Q

is there a vaccine for vs-FCV?

A
  • Core FCV vaccines have limited efficacy against vs-FCV
  • Vs-FCV vaccine - currently not recommended
    • Protects from homologous vs-FCV strain, but there are different field strains of vs-FCV
38
Q

Compare and contrast FCV and FHV-1

A
  • FHV-1:
    • Respiratory signs
    • Conjunctival and corneal lesions
    • Rhinitis with sneezing, bilateral serous nasal discharge
    • Clinical signs can be more more severe:
      • Obstructed nares, matting of eyelids, kittens - open mouth breathing, anorexia, dehydration, pneumonia
    • Dermatitis
    • Can cause oral ulcer
    • Fever, anorexia, lethargy with any if the above signs
  • FCV:
    • Highly variable combination of signs (strain dependent)
      • Respiratory signs
      • Oral and nasal ulcer
      • transient lameness
      • Pneumonia
      • Conjunctivitis
      • Dermatitis
    • Fever, anorexia, lethargy with any of the above signs

Virology (37 decks)

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