A retrospective study of the neuropathology and diagnosis of naturally occurring feline infectious peritonitis

Abstract

Feline infectious peritonitis (FIP) is one of the most important viral diseases of cats worldwide. Our study describes the neuropathology and the diagnostic features of 26 cases of FIP in domestic cats. The average age of affected individuals was 11.8 mo, and there was no sex or breed predisposition. Clinical neurologic signs were noted in 22 cases, and rabies was clinically suspected in 11 cases. Twenty cats had lesions in multiple organs, and 6 cats had lesions only in the brain. Gross neuropathologic changes occurred in 15 cases and consisted of hydrocephalus (10 cases), cerebellar herniation through the foramen magnum (6 cases), cerebral swelling with flattening of gyri (2 cases), and accumulation of fibrin within ventricles (2 cases) or leptomeninges (1 case). Histologically, 3 main distinct distributions of neuropathologic changes were observed, namely periventricular encephalitis (12 cases), rhombencephalitis (8 cases), and diffuse leptomeningitis with superficial encephalitis (6 cases). Fresh tissue samples were submitted for fluorescent antibody testing (FAT) after autopsy in 17 cases, and positive results were found in only 7 cases. Immunohistochemistry (IHC) for feline coronavirus confirmed the diagnosis in all 26 cases. IHC appears to be a more sensitive and reliable test for confirmation of FIP than is FAT.

Immunohistochemical studies on meningoencephalitis in feline infectious peritonitis (FIP)

“…1 to 3. These findings were in conformity with those in a recent report on FIP meningoencephalitis [15]. On the other hand, viral antigen was not detected in the brain of Case No.…”

“…FECV infection is asymptomatic or exclusively causes mild gastrointestinal clinical symptons, while FIPV causes fatal symptoms such as fever, anorexia, weight loss, abdominal distention and neurological symptoms in young cats [2,13]. The clinical symptoms differ depending on the form and organ distribution of the lesion, and in cases with lesions in central nervous system, neurological symptoms such as depression, ataxia and seizures appear in 85% of cases [15]. It was assumed that FIPV originating from FECV acquired its monocyte-or macrophage-tropism responsible for viral dissemination and developed specific FIP lesions due to vasculitis [17,18].The FIP lesions are characterized by localized or disseminated fibrinous, pyogranulomatous, or granulomatous inflammation with protein-rich effusion in the body cavities [9,10].…”

“…Lesions in the central nervous system (CNS) are frequently observed mainly in the leptomeninges, ventricles, choroid plexus and sometimes neuroparenchyma [5,12,16]. Although histopathological features of FIP lesions in the CNS have been well documented [6,14,15], the association between inflammatory cell types and the distribution of viral antigens remains to be clarified. The present study describes the inflammatory cell types and viral antigen distribution in the brain lesions of 4 cats diagnosed as FIP.…”

“…Pathological diagnosis of FIP is mainly performed by immunofluorescence (IF) using fresh tissues or immunohistochemistry on formalin-fixed paraffin sections [7]. Immunohistochemistry was believed to be more specific than IF [15], while some previous reports also raised questions about its specificity [4]. The antibody used in this study, FIPV3-70, is known to react with the nucleocapsid antigen of FIPV and is considered a valuable diagnostic tool for FIP [8].…”

The SARS-CoV-2 spike protein alters barrier function in 2D static and 3D microfluidic in vitro models of the human blood–brain barrier

“…nervous system resulting in neurological diseases 19 . Other coronaviruses have been shown to be neurotropic, causing encephalitis in felines 20 , porcine 21 and murine 22 . Additionally, SARS-CoV-1, the most closely related coronavirus, has been shown to infect the brain stem of both human and animals 23 and the first case of meningitis/encephalitis has been reported in a patient associated with SARS-CoV-2 24 .…”