44. Feline calicivirus infections.

Question 1

Causative agent?

Answer 1

Causative agent:

• Feline calicivirus (FCV), Vesivirus (can culture!)
• Susceptibility: domestic cat & other felids (i.e. cheetah), marine mammals, (dog)
• Mother cats can infect kittens with grooming (saliva spread)
• Resistance: survival in the environment for weeks (shelters); bleach 1:32 inactivates, resistant to
• detergents
• One serotype, but antigenic variants (maybe vax not effective towards all strains, esp highly
• pathogenic)
• Significant variance in virulence ʹ since 1998 highly pathogenic strains

Question 2

Occurrence, epizootiology?

Answer 2

Occurrence, epizootiology

• Present worldwide: more frequent in shelters and breeding catteries
• Shedding with excretions (ocular, nasal, oral): transmission by direct contact (indirect, airborne, low significance)
• Long-term carrier and continuously shedder cats (virus strain dependent)

‣ Persisting infections in the tonsils and nasopharyngeal mucosa

‣ Carry for minimum 30 days ➝ approximately 50% on Day 75

‣ Some cats are lifelong carriers and shedders

‣ FIV infection facilitates shedding

‣ Low, intermediate and high titre shedders ➝ recognition

‣ 20-30% of cats are carriers, vaccination does not influence

Question 3

Pathogenesis?

Answer 3

Pathogenesis

1. Oronasal infection ➝ pharynx ➝ viraemia ➝ lungs, mouth, throat, joint synovial membranes, pads, visceral organs

(very virulent strains)

2. Shedding in saliva, may be present in faeces and urine
3. Oral mucosa, pads ➝ blisters, epithel necrosis ➝ erosions, neutrophil infiltration
4. Lungs: alveolitis, exudative pneumonia, proliferative interstitial pneumonia
5. Joints: acute synovitis, thickened synovial membrane, liquid accumulation

Question 4

Clinical signs?

Answer 4

Clinical signs

• Differences in virulence & tissue-tropism: diverse clinical manifestations
• Viremia: on day 3-4; first fever , mild depression; second fever , lesions/signs
• (Vesicles) erosions: oral cavity- mainly on the margin of the tongue, lops, nose, pads, rarely skin,
• healing w/in 2-3 weeks
• Mild conjunctival & resp signs: sneezing, lacrimation (clear), nasal discharge, rarely pneumonia,
• dyspnoea, salivation, wet fur
• Lameness & fever (limping syndrome)
• Can be independent from the oral & resp signs
• May be immunocomplex mediated
• Associated with depression & pneumonia
• Usually complete recovery w/in 24-48h
• Has been observed after immunisation with live attenuated vaccine
• Virulent systemic FCV strains (VS-FCV) ʹ severe systemic syndrome
• Vasculitis, face & pad (50%), fever (90%), resp signs (50%), icterus (20%), nose & intestinal
• bleeding (30-40%), up to 60% lethality
• More severe in adults; in vaccinated cats too
• Chronic stomatitis: lymphoplastic gingivitis t=stomatitis complex, LPSG ʹ most of the patients
• are FCV shedders, but other factors(i.e. FIV, individual) may contribute ->anorexia
• (etiology unclear ʹ mostly FCV but some other conditions too)

Question 5

Pathology, histopathology?

Answer 5

Pathology, histopathology

• Erosions in the oral cavity, at the margin of the tongue
• Very virulent strains:
• vasculitis,
• enlarged liver,
• pneumonia,
• pancreatitis,
• pericarditis

Question 6

Diagnosis?

Answer 6

Diagnosis:

• clinical signs (+/-),
• oral, pharyngeal, tonsil swab:
• ELISA, IF , RT-PCR; virus isolation,(serology)

Question 7

Differential diagnosis?

Answer 7

Differential diagnosis

1. Feline rhinotracheitis: severe upper rep lesions, ocular lesions(keratitis)
2. Bordatella bronichiseptica: coughing, pneumonia
3. Chlamydophila felis: conjunctivitis, pneumonia
4. Lameness, arthritis: FLV, FFoV

Question 8

Treatment?

Answer 8

Treatment

• Supportive treatment, enteral nutrition, parenteral fluid, ABs, hyperimmune sera
• Ribavirin in vitro efficient, in vivo toxic ʹ so cannot use
• High titre neutralising Abs after recover from natural infection
• Maternal Abs protect for a few weeks, may persist for 10-14 weeks
• Attenuated & inactivated vaccines, usually bivalent (FCV, FHV) ʹ calici and herpes
• Live vaccines: cat can shed the virus and show clinicalsigns
• Residual virulence, shedding of attenuated strain
• Commercial vaccines: F9 & 225 strains ʹ relatively broad spectrum of protection
• Primary vaccination: 9-12 (& 16) weeks of age
• Vaccination may protect for 10-12 months ʹ yearly repetitions are necessary
• Vaccination may protect from signs, but not infection & becoming carrier
• Hygiene, management: closed farming, ID of shedders