A review of feline infectious peritonitis virus infection

Abstract

Feline infectious peritonitis (FIP) is an infectious disease characterized by non-specific laboratory changes and clinical signs. Clinical symptoms include anorexia, jaundice, fever, and weight loss. Moreover, some lesions are found in the digestive and respiratory systems. FIP, whose virulence varies, cannot be distinguished using several diagnostic methods. Moreover, feline coronaviruses (FCoVs) can be classified into two serotypes based on differences in their amino acid sequences, spike (S) protein sequences, and antibody (Ab) neutralization. There are two pathotypes, namely those caused by FCoV, which are often referred to as feline enteric coronavirus and FIP virus (FIPV). Furthermore, FIPV infection can be caused by sub-neutralizing levels of anti-FIPV S Abs. Therefore, a supporting diagnosis is needed to confirm FIP because there are no specific symptoms. This review aimed to provide updated information on FIP, including epizootiology, clinical and pathological characteristics, pathogenesis, hematology, clinicopathological and imaging features, pathological features, experimental infection, treatment and prevention, infection and immunity, animal and public health considerations.

Keywords: clinical; feline coronavirus; feline infectious peritonitis virus; infectious disease.

Figure-1

(a–f) Gross lesions in feline infectious peritonitis (FIP). Wet FIP is represented by serofibrinous and granulomatous serositis and granulomatous lesions in the liver (arrows). (b–f): Cats with dry FIP. Enlargement of mesenteric lymph nodes due to granulomatous inflammation. Jejunum with multiple granulomas in the serosa. Jejunum with small subserous granulomatous lesions in the veins (phlebitis and/or periphlebitis; arrows). Kidney with granulomatous and periphlebitis of the capsular vein (arrow). (f): Brain with multifocal granulomatous phlebitis and periphlebitis of the cortical leptomeningeal vein (arrow) [25].

Figure-2

(a) Ultrasound image of ascites. (b) Radiograph of a large amount of effusion in the abdominal cavity. (c) Presence of necrotic foci in the kidneys. (d) Ascites and enlarged lymph nodes. (e) Interstitial nephritis is characterized by inflammatory cell infiltration, including macrophages, lymphocytes, neutrophils, and plasma. (f) Presence of macrophages in the kidney using immunohistochemical staining [21].

Figure-3

Feline small intestine with extensive thickening of the intestinal wall characterized by dense, white, irregularly proliferating tissue that extends through the intestinal wall [26].

Figure-4

Abdominal effusion from a feline infectious peritonitis cat. Non-degenerated neutrophils with vacuolated hyperbasophilic cytoplasm (dashed arrow), two mesothelial cells (thick arrow), and scattered erythrocytes (thin arrow) embedded in a granular proteinaceous eosinophilic background [26].

Figure-5

Cat lung organ with severe, acute, diffuse fibrinous pleuritis accompanied by scattered inflammatory cells [22].

Figure-6

Feline liver pyogranulomatous hepatitis with intracellular positivity [22].

Figure-7

Kidney organs of feline infectious peritonitis cats experiencing granulomatous nephritis with positive presence of intracellular and extracellular granules [22].

Figure-8

The kitten’s stomach is very distended and accompanied by effusive feline infectious peritonitis. There is also an enlarged scrotum due to inflammation of the tunica [16].

Figure-9

Feline infectious peritonitis-related retinal hemorrhage and detachment [29].

Figure-10

Histopathologic slice of the eye. Mononuclear infiltration in the choroid and exudative retinal detachment are visible as fluid in the subretinal gap separating the retina from the choroid [29].

Figure-11

Histopathological and immunohistochemical characterization of feline infectious peritonitis lesions. (a) Fibrous exudation with diffuse serosal inflammation. (b) Renal granuloma development (type B lesion). (c) Numerous red cells or monocytes/macrophages in the same inflammatory region, as seen in (a). (d) Numerous monocytes/macrophages (red cells) within the same granuloma, as shown in (b). (e) Plasma cells and a multinucleated giant cell (upper right corner) within a type A lesion in the liver (cat no. 6). (f) Inflammatory cells (presumably macrophages) containing feline coronavirus (FCoV) antigen (red cells) within an intestinal granuloma. FCoV-positive granules are also present extracellularly. Stainings: (a, b, and e): hematoxylin-eosin, (c and d): lectin immunohistochemistry, and (f): FCoV immunohistochemistry. Magnifications: (a–d): 100×, (e): 400×, and (f): 200× [30].

Figure-12

(a-f) Feline infectious peritonitis in the lungs of cats [28].

Figure-13

Feline infectious peritonitis in a 12-year-old female cat: a longitudinal ultrasound image of the abdomen (case 9). (a) Between the calipers, a slightly thickened section of the parietal peritoneum is visible (2.6 mm). (b) The hyperechoic mesentery presents an uneven and nodular appearance (between calipers: 1.2 cm). Furthermore, an anechoic peritoneal effusion (asterisk) is observed [48].