Pyogranulomatous panophthalmitis in a ferret

Background

Ferret systemic coronavirus (FRSCV) disease is an emerging condition in domestic ferrets, which was first reported in 2004. Since then, additional cases have been reported in the United States, Europe, and Japan. Clinical presentation and pathology in FRSCV disease closely resemble that in the noneffusive (dry) form of feline infectious peritonitis (FIP) in domestic cats, which is caused by a group 1 feline coronavirus (FCoV).

Ferrets with systemic coronavirus disease typically display nonspecific clinical signs, including lethargy, vomiting, diarrhea, anorexia, weight loss, and loss of body condition. Physical examination may identify intra-abdominal masses, renomegaly, and splenomegaly. Signs of central nervous system involvement include acute or progressive hind limb paresis, ataxia, seizures opisthotonus, abnormal gait, and proprioceptive deficits. Frequently noted hematologic changes include nonregenerative anemia, elevated globulins, decreased albumin, and thrombocytopenia. Urinalysis abnormalities may include green urine, proteinuria, blood, and rare bilirubin crystals. Significant radiographic signs in ferrets with FRSCV include loss of lumbar musculature, decreased peritoneal detail, presence of mid-abdominal soft tissue masses, and splenomegaly. The majority of ferret cases with systemic coronavirus disease were noted to have ultrasonographic evidence of peritonitis, abdominal lymphadenopathy, splenomegaly, abdominal soft tissue masses, renomegaly, and changes in the renal cortex echogenicity.

Gross lesions observed in FRSCV disease consist of multifocal to coalescing, white to tan, irregular nodules, or plaques ranging from 0.5 to 2 cm diameter dispersed over serosal surfaces. The peritoneum, particularly the intestinal serosa and mesentery, is most commonly affected. Nodules can also be found on the surface or extending into the parenchyma of other organs, especially the liver, kidneys, spleen, and lung. The mesenteric lymph nodes are also involved in most cases.

Histopathologic examination of affected tissues is the gold standard to diagnose FRSCV. Histopathologic lesions are characterized by widespread pyogranulomatous perivasculitis and peritonitis nearly identical to the noneffusive form of FIP. Immunohistochemical analysis using anti-FCoV monoclonal antibody provides a definitive diagnosis by identifying positive staining for group 1 coronavirus antigen in foci of pyogranulomatous inflammation from ferrets with suspected coronavirus disease. Reverse transcriptase polymerase chain reaction (RT-PCR) assays have been developed and have the potential to differentiate genotypes of ferret coronavirus.

Systemic coronavirus disease in ferrets closely resembles FIP in domestic cats, including eye lesions. Ophthalmic manifestations can include anterior uveitis, chorioretinitis, optic neuritis, and retinal detachment.

Objectives

To describe pyogranulomatous panophthalmitis with systemic coronavirus disease in a domestic ferret (Mustela putorius furo).

Procedure

A 15-month-old spayed female ferret was presented with a history of lethargy and weight loss of 2 weeks duration. Upon physical examination, a 2-mm-diameter focal area of opacity was noted in the left cornea. In addition, the ferret was quiet, in poor body condition, and dehydrated. A complete blood count and plasma biochemistry revealed a severe nonregenerative anemia, azotemia, hyperproteinemia, hypoalbuminemia, and mild hyperphosphatemia and hyperchloremia. Urinalysis revealed hyposthenuria. Whole body radiographs showed multifocal thoracic nodular disease, splenomegaly, and renomegaly. Abdominal ultrasonography confirmed bilaterally enlarged kidneys, hypoechoic liver and spleen, and a caudal abdominal hypoechoic mobile nodule.

Results

The ferret was humanely euthanized, and a postmortem examination with subsequent histopathology showed multifocal necrotizing pyogranulomas in the lung, spleen, kidneys, mesenteric lymph nodes, and serosa of the duodenum. Pyogranulomatous panophthalmitis was diagnosed in the left eye. The multisystemic granulomatous lesions were suggestive of FRSCV. The presence of coronavirus in the left eye was confirmed by positive immunohistochemistry. RT-PCR on formalin-fixed, paraffin-embedded tissue from the lung, spleen, and kidney was negative for FRSCV and positive for ferret enteric coronavirus (FRECV).

Author Conclusion

This is the first report of ocular lesions in a ferret with systemic coronavirus disease, suggesting that ferrets presented with similar ocular lesions should also be evaluated for evidence of coronavirus infection.

Inclusions

Five figures, 23 references.

Editor Annotation

FRSCV is an increasingly recognized disease of ferrets, usually affecting young animals, with low morbidity but high mortality approaching 100%. Current research is focusing on determining the relationship of this virus with that of FRECV, a disease characterized by high morbidity, but relatively low mortality. Most ferrets with FRSCV are reported as thin, ill animals with pyogranulomatous lesions, including palpable abdominal masses.

This case is the first report of a ferret with apparent FRSCV and concurrent pyogranulomatous panophthalmitis. FRSCV has often been compared to FIP in cats. Ocular lesions are common in cats with FIP. Of interest is the observation that immunohistochemical staining confirmed coronavirus in multiple tissues including the eye. However, RT-PCR of lung, spleen, and kidney were positive for FRECV and not FRSCV. (AML)