Mp. France et al., Granulomatous peritonitis and pleuritis in interferon-gamma gene knockout mice naturally infected with mouse hepatitis virus, AUST VET J, 77(9), 1999, pp. 600-604
Objective To investigate a disease outbreak in a colony of laboratory mice
with targeted disruption of the gene for interferon-gamma
Format A case report based on necropsy, histopathology, serology and immuno
histochemistry.
Results Affected mice exhibited depression and variable ascites. Necropsy r
evealed a granulomatous peritonitis and pleuritis with extensive adhesions
although parenchymal lesions were minimal. Serum samples had high concentra
tions of antibody to mouse hepatitis virus and immunohistochemical examinat
ion revealed the presence of mouse hepatitis virus antigen in granuloma mac
rophages. Sere-logical testing for other infectious agents and bacterial cu
lture were negative and wild type mice kept in the same facility remained h
ealthy. Despite the association between the disease and mouse hepatitis vir
us infection, the precise role played by mouse hepatitis virus was not dete
rmined. While the disease is superficially similar to feline infectious per
itonitis (another coronavirus-induced serositis), differences exist between
the histopathological findings in these two conditions.
Conclusion This unusual disease process illustrates how new diagnostic chal
lenges can arise in novel mouse genotypes created through molecular genetic
s. Furthermore, the association between the disease and mouse hepatitis vir
us illustrates the importance of maintaining laboratory animals under speci
fic-pathogen free conditions.