UK DIAGNOSTIC LAB NEWS


FELINE INFECTIOUS PERITONITIS (FIP): NO KITTEN AROUND WITH THIS CORONAVIRUS!


Cleon G. Hendricks, DVM, MPH


Assistant Pathologist, Veterinary Pathology Murray State University Breathitt Veterinary Center


History A 19-week-old purebred, castrated male, Siberian Russian cat was obtained from a breeding facility in early March. Following an unspecified period of diarrhea that was not responsive to treatment, the kitten was presented to the primary care veterinari- an with notable icterus and anorexia. Te following day, the kitten had moderate pyrexia (104-105°F) that resolved over the following 24 hours. Over- night, the patient was tachypenic, with pleural and peritoneal effusion. Centesis of the fluid from both sites revealed yellow to rust color fluid. Te kitten is noted to be FeLV negative and is up to date on vaccinations.


Gross Examination


Te kitten was in good body condition. Te mucus membranes and subcutaneous tissues were diffusely light yellow. Te abdomen was distended by 40mL of gelatinous, golden yellow to red translucent flu- id (Figure 1). Te liver weighed 100g (4.78% of body weight; adult normal is 3 to 3.5%), and there were myriad 1-3mm diameter white-tan nodules throughout the parenchyma (Figure 1).


Te thorax contained 10mL of straw-colored trans- lucent gelatinous fluid (Figure 1). Te heart weighed 10g (0.48% of body weight; adult normal is 0.3 to 0.45% and less than 20g). Te lungs were firm, mot- tled red to pink, exuded clear fluid on cut section, and contained myriad white-tan nodules similar to those in the liver (Figure 1).


Samples of all major organs were collected, fixed in 10% buffered neutral formalin, routinely processed, and stained with hematoxylin and eosin for histolog- ic examination.


Gross Diagnoses Moderate pleural and peritoneal effusion Moderate multifocal chronic granulomatous hepati- tis and interstitial pneumonia Generalized icterus


Histologic Examination Approximately 15% of the hepatic parenchyma was necrotic. In these areas, hepatocytes were replaced by fibrin, admixed with neutrophils, plasma cells, mac-


14 KVMA News - Diagnostic Rounds


Figure 1. : Image obtained during necropsy. Golden yellow to straw colored, gelatinous fluid occupies both thoracic and abdominal cavities. Myriad white-tan nodules occupy the parenchyma of both liver and lungs.


rophages and edema (Figure 2). Hepatocytes within the periphery of the necrotic area show signs of de- generation (reduction in cell size, angular cytoplasm, and missing nuclei). Mesothelial cells covering the surface of the hepatocytes are plump (reactive). Ap- proximately 40% of the lung parenchyma was ne- crotic and many alveolar septa were expanded by fi- brin mixed with necrotic cellular debris, neutrophils, macrophages, lymphocytes, and plasma cells. Multi- focally, alveoli contained foamy macrophages, ede- ma, and fibrin (Figure 3). Splenic periarterial lym- phoid sheaths and lymphoid follicles within lymph nodes were hypocellular, with fewer lymphocytes than expected (lymphoid depletion). Foci of necrosis and inflammation similar to those within the liver were scattered throughout the spleen (Figure 4) and colon. Multifocally, loops of Henle contain granular to globular basophilic mineral.


Histologic Diagnoses Moderate multifocal acute fibrinosuppurative and histiocytic hepatitis, splenitis, lymphadenitis and colitis Moderate multifocal chronic active fibrinosuppura- tive interstitial pneumonia Diffuse lymphoid depletion


Ancillary Testing Fluorescent antibody testing on the liver was positive for Feline Coronavirus.


Final Diagnosis Feline Infectious Peritonitis/Feline Coronavirus (FIP/FIP), caused by mutated feline corona virus (FCoV)


Discussion First described in 1963, feline infectious peritonitis (FIP) is caused by a mutated form of feline corona-


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