60. Diseases of cats caused by coronaviruses.

Question 1

Info and epidemiology?

Answer 1

Feline coronaviruses (FECoV, FIPV)

• Feline enteric coronavirus (FECoV)
• Feline infectious peritonitis virus (FIPV) ➝ peritonitis, vasculitis, serositis
• Host species: cat, other Felidae

Epidemiology

• 2 serotypes

I. 80-90%, difficult to isolate

II. 10-20%, easier to isolate, recombinant CCoV (neutralised by CCoV antibodies

• Both serotypes have 2 pathogens ➝ FIPV: 5%, FECV: 95%
• CCoV, TGEV, SARS and other HCoV may infect and cause seropositivity in cats and they shed these viruses

Question 2

Pathogenesis?

Answer 2

Pathogenesis

• PO/nasal , replication: (primary tonsils) airways and intestines (ileum, colon) , viremia
• 95% elimination
• 5% mutant virus (monocyte, macrophage)
• cell-attached viremia
• ( Virus + AB + Complement -> immune complex; release of vasoactive molecules)
• Outcome of infection
• 5-10 % FIP
• Start shedding virus after 2nd day ʹ after shedding most become seronegative at different times
• 58%: shedding for 1 month
• 95%: shedding stops within 9 months
• 13% carrier for the rest of its life
• 4% full resistance to infection
• Seropositive animals
• 5-12% FIP within 4-8 weeks
• Rarely few months/years
• Immune complexes
• Through Ig Fc receptors
• Apoptosis of activated Tc (virokins)
• Type III hypersensitivity (immune- complex) strong Ab response -> effusive wet FIP
• Type -effusive (DRY) FIP
• Lymphocytopaenia, hyper-gammaglobulinaemia, IC deposition, C3 activation

Question 3

Clinical signs?

Answer 3

Clinical signs

• Young cat (Enteral): Uneven litter, Diarrhoea
• (between 5-7 weeks), Vomiting, Sneezing, nasal discharge
• Every cat (FIP): weight loss, recurrent fever, anorexia, lazier (dyspnoe)
• Large undulating belly
• Sudden increase of the abdominal volume
• Eye: cloudy iris, color change, haemorrhages
• Dry FIP: shaking, CNS signs

Question 4

Diagnosis?

Answer 4

Diagnosis

• • Laboratory
• • ELISA/VN high titers (over 1:400 but it can be FECoV)
• • Albumin/globulin ratio in effusion and blood = < 0.4 (normal is > 0.8)
• • Alpha-1-acid glycoprotein (APP) measurement with nephelometer
• • RT-PCR from macrophages
• • Rivalta test
• • 5 ml distilled water + 1 drop 98% acetic acid and mix in tube
• • Layer 1 drop of effusion on top
• • Positive = shape of drop does not change, drop does not sink or sinks but slowly without changing shape (86% reliability)
• • Negative: the drop disperses completely (97% reliability)
    *

Question 5

Treatment?

Answer 5

Treatment

• If the cat survives it wasnt FIP( DDx cardiomyopathia non-infectious hepatosis, tumors)
• Immunosuppression + antibiotics
• Remove fluid from thorax
• Example:
• Ampicillin 10-20mg/kg every 8 hours
• Thalidomide (B) 50ʹ100 mg/day
• Prednisone 2-4 mg/kg (B, T) every 24 hours
• Cyclophosphamide 2.5 mg /kg, 4x a week
• Interferon (human) start with:104ʹ106IU/kg, later: 1ʹ50 IU/kg per day
• (after 3-7 weeks effectivity decreases because of an antibody response against it)
• Side effects after parenteral application (oral milder)
• Recombinant cat interferon (rFeIFN):106IU/kg every 4 hours

Question 6

Vaccine?

Answer 6

Vaccine

• Local protection with attenuated temperature-sensitive mutant - May protect from FECoV infection
• Induction of Tc response
• Subunit and DNA vaccines (Not S!!!!)

Question 7

Pathology?

Answer 7

Pathology

• Kidney
• Abdominal fluid
• Non-purulent inflammation in brain (accumulation of cytotoxic T-cells)