This year we decided to create profiles that would help specialists to diagnose, management and monitor feline infectious peritonitis (FIP). In this blog post, we explore how they can be used.

Dry FIP: we offer an extensive blood chemistry profile, including complete blood count, full clinical biochemistry and electrophoresis.

We are updating this essential database with the addition of the measurement of feline alpha(1)-acid glycoprotein (fAGP), an acute-phase protein that is highly useful in suspected FIP – (see also our recent blog post: The return of a great classic: Feline AGP (ALPHA-1 Acid Glycoprotein)) – and the measurement of feline coronavirus antibodies through IIF (indirect immunofluorescence).

The issue with patients with dry FIP is the lack of specificity in many clinical and pathological symptoms of chronic inflammation: the definitive confirmation of these forms would require direct identification of the coronavirus in parenchymal lesions, through immunohistochemistry and/or molecular biology (PCR). These procedures are invasive, because they must use biopsies, and are not always simple to carry out.

The presence of typical blood chemistry/electrophoretic alterations associated with an average/high IIF antibody titre and a high concentration of AGP, would heavily tend to support a clinical suspicion of dry FIP. In particular, in the case of FIP, the complete blood count included in the extensive profile makes it possible to detect non-regenerative normocytic normochromic anaemia, or possibly microcytic anaemia, associated with neutrophilic leukocytosis and/or lymphopaenia.

The biochemical picture may detect alterations in one or more organs, with particularly frequent alterations being those indicative of kidney damage (increased creatinine and urea) and liver damage (increased ALT, ALP and bilirubin), but especially hyperproteinemia, hypoalbuminemia and inverted albumin/globulin ratio.

These latter alterations can be studied more closely with the electrophoresis included in the profile, which in FIP usually shows an increase in alpha2- and gamma-globulins, as well as the calculation of the fAGP, which in FIP is usually very high (usually >1500 ug/mL).

Figure 1. Capillary electrophoresis of serum proteins in a cat with FIP, with hypoalbuminemia and marked polyclonal gammopathy
Figure 1. Capillary electrophoresis of serum proteins in a cat with FIP, with hypoalbuminemia and marked polyclonal gammopathy

Effusive FIP: compared to dry FIP, the effusive forms have the advantage of allowing for a coelomic effusion analysis, which in many cases makes it possible to confirm the diagnosis. In addition to complete blood chemistry and the measurement of fAGP, which make it possible to detect the typical alterations described above, we carry out a simultaneous cytochemical analysis of the coelomic effusion and search for the virus in the sample for PCR.

Effusions of patients with FIP have chemical characteristics (high proteins, albumin/globulin ratio often < 0.8, high LDH with high ratio between LDH and total cells present in the effusion) and cytological characteristics (presence of a non-septic exudate with low cell concentration, proteinaceous base and prevalence of non-degenerate neutrophils) highly suggestive of FIP. A positive fluid PCR 100% confirms the FIP diagnosis (high specificity), even if the sensitivity of the molecular biology is not absolute (sensitivity of around 70-80%). FIP monitoring: in cats with a confirmed FIP diagnosis, we offer a monitoring profile of the treatments carried out through a basic blood chemistry profile and measurement of fAGP. Clinical monitoring must be accompanied by an improvement in the classic blood chemistry alterations of the disease and a reduction in fAGP.

Catteries, colonies and breeding farms: it is known that the coronavirus responsible for FIP derives from feline enteric coronavirus through genetic mutations that make it capable of infecting the macrophages and invading the tissue: the greater the flow and replication of enteric coronavirus among the cats, the more likely it is that cases of fully developed FIP will be observed.

In settings with high potential circulation of feline coronavirus, we have two potential monitoring methods at our disposal.

Serology through IIF helps us understand the level of exposure of the cats present in that setting to previous infections.

In addition, testing for the coronavirus in faeces can help us understand who the eliminatory subjects might be, though it should be remembered that virus elimination through the faeces can be irregular and remittent, even in completely asymptomatic patients.

For proper prevention, it is therefore important to reduce the number of cats in the setting as much as possible and use repeated serological and/or PCR tests on the faeces over time, carried out as “random samples” on each group of animals and with a variable frequency based on the number of cats present (more often, e.g. once a month, if there are many cats, less often if there are fewer cats).

Saverio Paltrinieri, Med. Vet. EBVS European Specialist in Veterinary Clinical Pathology (Dipl. ECVCP); University of Milan
Walter Bertazzolo, Med. Vet. EBVS European Specialist in Veterinary Clinical Pathology (Dipl. ECVCP); Scientific Director of MYLAV