Feline infectious peritonitis

Question 1

What causes FIP?

Answer 1

A fatal combination of:

• a feline specific coronavirus (this is a feline specific disease)
• ineffective/inappropriate immune response

Question 2

Discuss feline enteric coronavirus (FECV)?

Answer 2

Common virus in all cat populations

Transmitted via faecal –> oral route

Prevalence increases in multi cat households (Cat shelters, breeding colonies, less likley in single cat households)

Highly contagious

Survives:

• 1-2 days at room temperature
• up to 7 weeks in dry environment
• Inactivated by most disinfectants

Question 3

Discuss disinfection of FECV?

Answer 3

Not something that persists in the environment very well. Opportunity of infection comes from a cat that is shedding the virus but normal disinfectants should prevent this.

Question 4

What are the presenting signs of feline coronavirus?

Answer 4

Typical signs of feline coronavirus infection

• Asymptomatic?
• Enteritis
  
  • mild self limiting vomiting and/or diarrhoea
  • can persist for weeks to months as chronic low grade GI signs
• Mild upper respiratory tract signs? (way of differentiating from cat flu is respiratory signs fairly mild with GI signs on top)

Question 5

Discuss feline coronavirus facts and figures?

Answer 5

Coronavirus specific antibodies are present in up to

• 90% of cats in catteries*
• 50% of cats in single cat households*

Viral shedding can occur for 7-18 mths post infection**

• intermittent or persistent
• higher levels of coronavirus shed by kittens

Approx 1/3 rd of antibody +ve cats shed virus**

• Only 5-12 % of infected cats go on to develop the fatal clinical syndrome of FIP

Take home message: Coronavirus causes FIP but not in all cats!!

Question 7

Does signalment help with FIP diagnosis?

Answer 7

A disease of younger cats?

• cats < 3 years of age
• most prevalent from 4-16 months?
• but can occur in cats of any age….
• 2ry peak in cats>10 yrs

A disease of multicathouseholds?

• increased exposure to virus?

stress related

• recent rehoming or neutering?
• concurrent illness?
• shelter cats?

A disease of pedigree cats?

genetic susceptibility?

• Abyssinian, BSHs, Birmans, Burmese
• litter mates at ­ risk

Question 8

What is indicative of FIP in this pic?

Answer 8

Kitten with URT signs mucopurelent occular discharge and nasal discharge

Question 9

Discuss the angelic kitten phenomenon associated with FIP?

Answer 9

The trouble with it is it effects young kittens creating angelic kittens because they are ill and not being the little mad things kittens usually are so appear quiet and snuggly but they actually are ill.

Question 10

Discuss the categories of wet and dry FIP?

Answer 10

We used to think of categories with FIP:

“Wet FIP”= cats which develop ascites and/or pleural fluid associated with vasculitis

“Dry FIP” = cats that develop granulomatous lesions in multiple organs but often no effusion

We now appreciate there are probably in between stages as well or one might progress to the other.

Question 11

Discuss the ‘wet’ FIP presenting signs?

Answer 11

• Abdominal distension due to ascites
  
  • modified transudate/exudate (non septic)
• Pleural effusion causing
  
  • tachypnoea
  • dyspnoea (restrictive breathing pattern)
  • muffled heart and lung sounds
• Many cats with “wet” (effusive) FIP will also have the clinical signs of “dry” FIP and vice versa

Question 12

What is a restrictive breathing pattern?

Answer 12

Shallow and rapid resp pattern in auscultation it sounds like muffle heart and lung sounds.

Question 13

What is a modified transudate/exudate?

Answer 13

Modified transudates are a type of effusion whose cell count and protein content are intermediate between a transudate and an exudate. In some cases, modified transudates may represent a transitional stage before the development of an exudate (as with uroabdomen, which begins as a modified transudate but develops into a chemical exudative peritonitis over time). Modified transudates arise as a result of disruptions to the endothelium or imbalances in the Starling forces. Common causes include:

• Increased vascular hydrostatic pressure resulting from inappropriate activation of the renin-angiotensin-aldosterone system (RAAS) in portal hypertension or congestive heart failure.
• Vasculitis, caused by feline infectious peritonitis virus (FIPV) or neoplasia. (Further discussion of the effusion encountered with FIP.)
• Strangulation of abdominal or thoracic organs may lead to the production of a modified transudate (which will develop into an exudate if untreated). This may occur with lung lobe torsion, torsion of the spleen or of a liver lobe or if part of the liver becomes strangulated within a diaphragmatic rupture.
• Chylous effusions are sometimes considered to be a type of modified transudate.

Question 14

What are the presenting signs for Dry FIP?

Answer 14

• Mild intermittent fever- waxes and wanes
• Poor appetite
• Weight loss/stunted growth
• Depression (which can sometimes be confused for angelic kitten syndrome)
• Anaemia
  
  • mild, non regenerative
  • if more severe might be 2ry to IMHA?
• Jaundice?
• Abdominal palpation might reveal
  
  • enlarged mesenteric LNs
  • irregular and enlarged kidneys/liver
  • intestinal mass lesions
• Ocular signs of FIP
  
  • uveitis (keraticprecipitates, anisocoria, blepharospasm)
  • chorioretinitis (perivascular cuffing)
  • retinal detachment (sudden blindness)
  • hyphaema, hypopyon
• Neurological signs (variable)
  
  • dull, abnormal mental state
  • can overlap with severe lethargy?
  • ataxia, nystagmus
  • seizures

Question 15

Discuss presenting signs for FIP?

Answer 15

• Sometimes there are very few useful findings on physical examination and the history can be very vague…..
• These cats have often been seen a few times before it’s clear something significant is going on.
• Waxing and waning disease especially with fever can mimic infections which seem initially to respond to treatment with antibiotics.
• This is the same as a range of immune mediated diseases.
• Dry form can be more challenging as no obvious effusion

Question 16

FIP mimics which other diseases?

Answer 16

DDx: include lymphocytic cholangitis, lymphoma

Question 17

Describe this US exam of FIP?

Answer 17

Question 18

Why do cats develop clinical FIP?

Answer 18

“The internal mutation theory”

• A cat is infected with FECV (feline enteric coronavirus)
• phase of rapid replication occurs in enterocytes
• A mutation occurs allowing virus (FIPV feline infectious peritonitis virus) to replicate in macrophages
• sustainable replication in macrophages then triggers a fatal systemic disease
• characteristic histopathology lesions are useful markers for the disease:
  
  • vasculitis affecting serosalsurfaces
    
    • causes pleural, peritoneal & pericardial fluid
  • pyogranulomatous or granulomatous lesions in multiple organs
    
    • lymph nodes, liver, kidney, GI tract often affected

Question 19

In a nutshell why do cats develop clinical FIP?

Answer 19

We don’t know everything but in a nut shell… Contributing factors in pathogenesis of FIP include

• viral genetics
• host immunity
  
  • VN Ab (virus neutralising antibody) should be protective in viral infections
    
    • in FIP humoral Ab may contribute to pathogenesis via the mechanism of Ab mediated enhancement
  • more positive role for cell mediated immunity but…
    
    • weak CMI-wet FIP?
  • intermediate CMI (cell mediated immunity)-dry FIP?
• litter mates are at risk due to genetic and environmental factors

Question 21

How to diagnose FIP?

Answer 21

Can be difficult as it mimics other things and it is a high stakes condition to report back to the breeder

Question 22

Discuss FIP diagnosis?

Appropriate clinical suspicion? Findings on haematology?

Answer 22

FIP: diagnosis

Appropriate clinical suspicion based on

• signalment
• clinical history
• physical examination

AND appropriate clinical suspicion based on

• findings on haematology
  
  • lymphopenia + neutrophilia (variable, common stress leucogram in cats)
  • mild-moderate non regenerative anaemia
  • changes associated with 2ry IMHA
    
    • regenerative anaemia

Question 23

Discuss findings on Biochemistry for FIP?

Answer 23

Findings on serum biochemistry

• hyperproteinaemia (50-70% cats)
  
  • high globulins (gamma globulins)
    
    • polyclonal or monoclonal on SPE (serum protein electropheresis)
• low albumin:globulinratio
  
  • low albumin (not low enough to explain the ascites though)
    
    • due to renal and /or GI loss, loss in fluid associated with vasculitis, reduced production by liver
  • <0.4= FIP likely, >0.8 = FIP unlikely
• high bilirubin
  
  • quite common in “wet” FIP
• high serum alpha-1 acid glycoprotein
  
  • non specific acute phase protein but can be helpful in some cases

Question 24

Discuss FIP diagnosis from fluid analysis?

Answer 24

fluid analysis (pleural or peritoneal)

• clear yellow viscous fluid
  
  • high protein (>35g/l)
  • albumin:globulin<0.4-suggests FIP, >0.8-unlikely FIP
  • cell content can be low but very variable
    
    • non degenerate neutrophils and macrophages
• rare cases where fluid is chylous

Question 25

Have a look at this fluid analysis?

Answer 25

Question 26

How can we diagnose FIP in diagnostic imaging?

Answer 26

Diagnostic imaging

• peritoneal, pleural and/or pericardial fluid
• enlarged mesenteric lymph nodes
• irregular kidneys, may be enlarged
• intestinal wall lesions

Question 27

What must we remember about diagnosing FIP?

Answer 27

• We cannot rely on “one single diagnostic test”- this is often the case in small animal medicine.
• Cumulative evidence is important when trying to make a diagnosis of FIP

Question 28

Discuss this radiograph of FIP?

Answer 28

If you can’t see the cardiac outline clearly on a DV view of the thorax- pleural fluid is likely to be the cause.

Question 29

Discuss this radiograph and US of cat with FIP?

Answer 29

Fairly typical radiograph of FIP kitten.

Loss of serosal detail in abdo so ascitic.

Dilated loops of intestine/generalised dilation which caries on into the colon this is not consistent with obsrtruction

Chunky irregular meseneteric LN

Question 30

Discuss this US of FIP kidneys?

Answer 30

• Irregular margins loss of cortico medullary definition, patchy changes created by sterile abcesses in them causing this heterogenous appearance
• d/d for this type of appearance would be renal lymphoma

Question 31

If we have a high index of clinical suspicion based on all our findings, can we confirm our suspicion with specific tests for virus?

Answer 31

Feline CoV serology indicates exposure only

• very high titres support a presumptive diagnosis if very high clinical suspicion
• rising titres not useful unlike other diseases
• can run titres on fluid samples as well as blood but same reservations apply

feline CoV RealTime PCR (tissue, fluid…not blood)

• cannot differentiate between FIPV and “normal” coronavirus (FECV) but if virus is present in any fluid sample this supports a diagnosis
• faecal samples used to identify chronic viral shedders
  
  • ?role if trying to eliminate infection from catteries/breeding colonies

Can’t differentiate frim pathogenic FIPV and FECV which just gives mild diarrhoea on these tests alone

Question 32

Discuss FIP diagnosis?

Answer 32

FIP:

Diagnosis If we have a high index of clinical suspicion based on all our findings, can we confirm our suspicion with specific tests for virus?

• immunofluorescence to detect FCoV antigen in macrophages
  
  • samples to use: effusion if possible, CSF if neuro signs
• +ve staining is consistent with FIP
• useful test to confirm a strong clinical suspicion
• false negatives if low cellularity in effusions

Why is this important?

• To become pathogenic with respect to FIP FCoV must undergo sustained replication in macrophages –> this triggers a fatal systemic disease.

Question 33

Is there a definitive diagnosis for FIP?

Answer 33

Histopathology (invasive) to look for typical lesions

• Tissue sample most definitive way of proof of disease
• perivascular pyogranulomatous or granulomatous lesions in multiple organs
  
  • macrophages and neutrophils +/-lymphocytes and plasma cells
  • there are other possible causes…
  • request immunostaining to look for FCoVantigen in tissue macrophages in any suspicious cases
• vasculitis
• Post mortem diagnosis: the gross appearance of FIP is quite typical but always submit samples for confirmation

Question 34

How should FIP be managed?

Answer 34

Supportive care (because there is no effective treatment)

• Anti inflammatory
  
  • prednisolone 0.5mg/kg bid
    
    • no evidence to support use of higher immunosuppressive dose
    • might improve quality of life for a while –> increase in appetite?
• appetite stimulants
  
  • mirtazapine
• vitamin B12 (cobalamin)?
• s/c fluids at home?
  
  • would you consider a feeding tube to provide water and nutrition?
    
    • welfare discussions/ethical issues if the disease is incurable?
    • would improve quality of life?
• anti oxidants?
  
  • s-adenosylmethionine
• Feline interferon omega
  
  • immune modulator
    
    • 1 st reports of use 10 + yrsago
    • still no convincing evidence for improved survival
• Euthanasia is an important option we must discuss with owners on welfare grounds.

Question 36

Discuss FIP prevention?

Answer 36

No vaccine currently available in the UK

• controversial
• FIP is a type of immune disease-could vaccination increase the risk?
• even natural infection with FECV doesn’t give immunity, why would a vaccine work?

Reduce transmission of coronavirus

• litter trays or outdoors?
• food and water bowls separate to trays
• reduce numbers of cats
• reduce stress
• identify shedders? Rehome to single/indoor cat househoulds

Early weaning of kittens?

• isolate queen 2 weeks pre term
• MDA (maternally derived antibodies) reduces at 5-6 weeks

welfare?

Question 37

Why is there so much conflicting information about FIP?

Answer 37

• Variable disease with a variable course
  
  • Studies have looked at different populations of cats in different countries
• Diagnosis can (but does not always have to) be challenging
• Survival times poor but variable which leads to confusion over claims for success with treatment
• A confirmed diagnosis has traditionally needed histopathology –often at post mortem
  
  • this final definitive diagnosis is sometimes missing

Question 38

Is the cat with FIP we have had in the clinic a risk to other cats?

Answer 38

Normal nursing and hygiene precautions are usually adequate

• keep in individual kennel
• avoid direct contact with other patients
• often only limited shed of FECV by this stage

To develop FIP cats have usually got additional risk factors and have been exposed to high loads of FECV

Suspected FIP cats do not need to be kept in isolation unlike cats with Feline infectious enteritis

Question 39

Discuss ex lap and FIP?

Answer 39

Exploratory surgery inevitably does happen in some FIP cases where the diagnosis has been missed in other ways or the disease is mimicking a surgical disease- always collect biopsies at least and then a diagnosis can be made ie make the best of a bad situation.

Question 40

Useful links for FIP?

Answer 40

http: //www.icatcare.org/advice/cat-health/feline- infectious-peritonitis-fip
http: //www.sheltermedicine.com/library/resources/f eline-infectious-peritonitis-feline-coronavirus-fip- fcov