Using direct immunofluorescence to detect coronaviruses in peritoneal in peritoneal and pleural effusions

Abstract

Twenty‐one cases of feline infectious peritonitis (FIP) were diagnosed using a direct immunofluorescence test on cytocentrifuged pleural and peritoneal effusions from cats sampled in vivo (11 cases) and at necropsy (10 cases). A commercial fluorescent polyclonal antiserum of feline origin reacting with FIPV and cross reacting with transmissible gastroenteritis virus and canine coronavirus was used. Eleven cats with ascites of a different origin were used as negative controls. The direct immunofluorescence test was 97 per cent reliable (31 cases of 32) and can be used in routine diagnosis.

Feline infectious peritonitis

“…In a study by Parodi et al [141], an immunofluorescence assay detecting intracellular FCoV antigen in cells within effusion was used; however, the number of cats enrolled in that study was limited. Hirschberger et al [84] detected FCoV antigen in 34 of 34 samples from cats with FIP-induced effusions.…”

Risk factors for feline infectious peritonitis in Australian cats

“…4 A positive histological diagnosis is characterised by fibrinous-granulomatous serositis, granulomatous-necrotising vasculitis and granulomatous inflammatory lesions in multiple organs. 2 Definitive diagnosis of FIP involves detection of FCoV antigen within macrophages using direct immunofluorescence (DIF) or immunohistochemistry (IHC) [7][8] and these two tests are now considered the gold standard. 4 Like IHC, DIF is highly specific (~100%) 7-11 but its sensitivity is variably reported from 95% 8,10 to as low as 57% 11 compared with histology, previously considered the gold standard.…”

In Vivo Diagnosis of Feline Infectious Peritonitis by Comparison of Protein Content, Cytology, and Direct Immunofluorescence Test on Peritoneal and Pleural Effusions

“…These cats had a yellowish, dense, and fibrinous effusion in the abdomen (63%) or in the chest (22%) or in both the cavities (15%) and had typical DIF-positive FIP lesions. 2,9,15 In the other 31 cats, the effusions were due to diseases other than FIP. Neither macroscopic and histologic typical lesions or anti-FCoV DIF-positive cells were found.…”

“…9,11-13 Although FCoV RNA has been demonstrated in the plasma of healthy cats in FECV-endemic catteries, 6 FCoVs detected from areas other than the intestinal lumen should be interpreted as FIPV, particularly if the viruses are detected in lesions 15 or effusions. 2 In this study, the results obtained using 3 different diagnostic methods (anti-FCoV direct immunofluorescence test, cytology, and protein analysis) for 110 cats with effusions over a 5-year period were compared to determine the utility of these methods for diagnosing FIP from analysis of the effusion alone. Cats with clinically detectable effusion were examined (Table 1), although in some cases clinical and laboratory data (serum chemistry, ultrasonography, macroscopic appearance of the effusion) suggested diseases other than FIP.…”

“…2 The slides were fixed and dehydrated in acetone : methanol (3:1) for 20 minutes and incubated for 30 minutes at 37 C in a moist chamber with 100 l of a feline polyclonal fluorescein-conjugated antiserum d detecting FCoV biotypes I and II and cross-reacting with TGEV and CCV. After washing 4 times for 10 minutes each with a 25% solution of carbonate buffer (pH 9), the slides were mounted in buffered glycerol and examined using a fluorescent microscope at 250-400ϫ magnification.…”