Feline Infectious Peritonitis
edt September 13, 2015
The Feline Infectious Peritonitis guidelines were first published in the Journal of Feline Medicine and Surgery (2009) 11, 594-604; the present update has been authorised by Diane Addie and edited by Karin Möstl.
The feline infectious peritonitis guidelines that the present article is updating were published in J Feline Med Surg 2009; 11: 594-604 and updated in J Feline Med Surg 2013; 15: 536; this update has been compiled by Diane Addie.
There have been too many major recent developments in the field of FCoV and FIP to sum up in a small paragraph, so a full updated ABCD FIP guideline will be published in the near future.
FIP diagnosis: amongst the most interesting of the developments is the advent of a commercially available RT-PCR test which distinguishes mutations on the spike of type I FCoVs which are associated with the development of systemic spread of the virus.1 There is a question of this test not being as sensitive as conventional FCoV RT-PCR, not only because it does not detect type II FCoVs, but also because the spike protein is the protein most subject to evolutionary immune pressure, and so the spike gene is the most variable of the coronavirus genes, and so primers may not bind, giving a false negative result.
It is the view of ABCD that RT-PCR is a preferred method of FIP confirmation in effusions, over immunofluorescence of macrophages, which is less widely available and more prone to human error.
In a comparison of commercially available FCoV antibody tests, sixteen uses of FCoV antibody tests were presented: sensitivity was deemed extremely important because many uses of FCoV antibody tests involve excluding FIP diagnosis or FCoV infection.2 An in-house ELISA test fared best both in terms of sensitivity and specificity and quantity of sample required (only 5 microlitres). The most sensitive rapid immunomigration (RIM) tests were identified. RIM tests fared best in rapidity of result, which is useful when screening a healthy cat, but they may give false negative results if used to support FIP diagnosis on effusion samples, due to binding of virus to antibody, rendering the antibody unavailable for the test antigen.3
For treatment polyprenyl immunostimulant (PPI, Sass & Sass) is only for use in non-effusive FIP, with no efficacy in effusive FIP. One study of 3 non-effusive FIP cases published reported survival of 14 months for one cat and over 2 years for 2 cats.4 (EBM grade IV) However, a conference abstract report of 58 cats showed only 22 % survival at 6 months and 1 cat at a year.5 (EBM grade III) A placebo controlled study is required.
Gil et al6 showed that in FeLV/FIV infected cats feline interferon omega therapy showed a tendency to reduce FCoV shedding (EBM grade III).
Chloroquine inhibits FCoV replication in vitro and has anti-inflammatory effects in vivo.7 However, survival times were only around 30 days at best and it increased alanine aminotransferase: so ABCD does not recommend its use until further studies have demonstrated significant benefit.
A placebo-controlled double blind trial on propentofylline showed no efficacy.8 (EBM grade I)
1 Porter E, Tasker S, Day MJ, Harley R, Kipar A, Siddell SG, et al. Amino acid changes in the spike protein of feline coronavirus correlate with systemic spread of virus from the intestine and not with feline infectious peritonitis. Vet Res 2014; 45: 49.
2 Addie DD, le Poder S, Burr P, Decaro N, Graham E, Hofmann-Lehmann R, et al. Utility of feline coronavirus antibody tests. J Feline Med Surg 2015; 17 (2): 152-162.
3 Meli ML, Burr P, Decaro N, Graham E, Jarrett O, Lutz H, et al. Samples with high virus load cause a trend toward lower signal in feline coronavirus antibody tests. J Feline Med Surg 2013; 15(4): 295-299.
4 Legendre AM and Bartges JW. Effect of Polyprenyl Immunostimulant on the survival times of three cats with the dry form of feline infectious peritonitis. J Feline Med Surg 2009; 11(8): 624-626.
5 Legendre AM. Polyprenyl Immunostimulant presentation to AAHA abstract, 2013.
6 Gil S, Leal RO, Duarte A, McGahie D, Sepúlveda N, Siborro I, et al. Relevance of feline interferon omega for clinical improvement and reduction of concurrent viral excretion in retrovirus infected cats from a rescue shelter. Res Vet Sci 2013; 94(3): 753-763.
7 Takano T, Katoh Y, Doki T and Hohdatsu T. Effect of chloroquine on feline infectious peritonitis virus infection in vitro and in vivo. Antiviral Res 2013; 99(2): 100-107.
8 Fischer Y, Ritz S, Weber K, Sauter-Louis C and Hartmann K. Randomized, placebo controlled study of the effect of propentofylline on survival time and quality of life of cats with feline infectious peritonitis. J Vet Intern Med 2011; 25(6): 1270-1276.
9 Addie D, Bélak S, Boucraut-Baralon C, Egberink H, Frymus T, Gruffydd-Jones T, et al. Feline infectious peritonitis. ABCD guidelines on prevention and management. J Feline Med Surg 2009; 11: 594-604.
Feline coronaviruses (FCoV) belong to the family Coronaviridae, subfamily Coronavirinae of the Order Nidovirales (de Vries et al, 1997). Coronaviruses are large (>120 nm), roughly spherical, enveloped, positive-sense single-stranded RNA viruses (Lai and Holmes, 2001). The name is derived from the Latin corona, meaning crown, wreath or halo, and refers to the fringe of bulbous surface projections - the peplomers - reminiscent of the solar corona (Fig. 1). This morphology is created by the viral spike (S) peplomers, which are proteins that populate the surface of the virus and determine host tropism.
With a genome of 27 to 32 kb, encoding a ~750-kDa replicase polyprotein, four structural proteins (S for spike, M for matrix, N for nucleocapsid, and E for envelope; Figs. 2, 3) and up to five accessory non-structural proteins, coronaviruses are the largest RNA viruses known to date (Brown and Brierly, 1995; de Vries et al, 1997). - A biologically important characteristic of these viruses is their capability to undergo recombination (Lai, 1996; Lai and Holmes, 2001).
Together with the canine coronavirus and transmissible gastroenteritis virus of pigs, FCoVs belong to the group I coronaviruses, defined by antigenic and genomic properties.
Feline coronaviruses have been assigned to two types, which are defined by antigenic and genomic properties. Type 1 virus is the most prevalent FCoV (Hohdatsu et al, 1992; Addie et al, 2003; Vennema, 1999; Kummrow et al, 2005; Shiba et al, 2007); the less common type 2 viruses are recombinants between type 1 FCoVs and canine coronavirus (CCV; Fig.4) that have repeatedly and independently arisen in the field (Herrewegh et al, 1998). Most studies have been conducted on type 2 viruses which can be easily propagated in cell culture (Pedersen et al, 1984). Importantly both virus types can induce FIP.
Previously, FCoV strains have also been allocated to two “biotypes”: feline enteric coronavirus and feline infectious peritonitis virus (FIPV; Pedersen, 1987). However, since all FCoV may induce systemic infections, as demonstrated by RT-PCR studies, this terminology should be avoided.
Feline coronaviruses can survive for up to seven weeks in a dry environment (Scott, 1988) and can therefore be transmitted indirectly e.g. via litter trays, shoes, hands and clothes. Indirect transmission may also occur at cat shows. However, FCoV is readily inactivated by most household detergents and disinfectants.
Ascites is the most conspicuous clinical manifestation of the effusive form (Fig. 11; Holzworth, 1963, Wolfe & Griesemer 1966). Thoracic and pericardial effusions may occur in combination with or separate from abdominal effusion (Figs. 5, 6). In cases where effusion is restricted to the thorax, the cats usually present with dyspnoea. Serositis can involve the tunica vaginalis of the testes, leading to scrotal enlargement.
The non-effusive, "dry" form of FIP is often a diagnostic challenge. Pyrexia, anorexia and lethargy may be the only signs, particularly in the early stages. More characteristic signs will depend on the organs or tissues involved in the vasculitis and pyogranulomatous lesions. Abdominal organs are a common site for lesions (Fig. 12). Renal involvement may lead to renomegaly detectable on palpation. Mural lesions in the colon or ileo-caeco-colic junction occasionally occur and may be associated with chronic diarrhoea and vomiting. There may also be palpable enlargement of the mesenteric lymph nodes, which may be misinterpreted as neoplasia (Kipar et al, 1999). - A diffuse pyogranulomatous pneumonia is seen in some cases leading to severe dyspnoea (Trulove et al, 1992).
Ocular involvement is common, leading to changes in iris colour, dyscoria or anisocoria secondary to iritis, sudden loss of vision and hyphaema. Keratic precipitates can be seen (Figs. 13, 14) and may appear as “mutton fat” deposits on the ventral corneal endothelium (Davidson, 2006). The iris may show swelling, a nodular surface, and aqueous flare may be detected. On ophthalmoscopic examination chorioretinitis, fluffy perivascular cuffing (representing retinal vasculitis), dull perivascular puffy areas (pyogranulomatous chorioretinitis), linear retinal detachment and fluid blistering under the retina may be seen (Fig. 15).
Neurological signs are reported in ≥10% of cases (Rohrer et al, 1993). They reflect focal, multifocal, or diffuse involvement of the brain, the spinal cord and meninges. The most commonly reported signs are ataxia, hyperaesthesia, nystagmus, seizures, behavioural changes and cranial nerve defects (Kline et al, 1994; Timman et al, 2008).
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