Poxviruses

Ectromelia or mousepox is a fatal disease in mice induced by infection with ectromelia virus. The disease is most severe in DBA, C3H, and Balb/c mice, while black strains seem to be relatively resistant and even may harbor latent infections.116,117,118 Prevalence of the overt disease may vary from few to all.119 The virus infects through skin lesions, and after approximately 10 days of incubation, the infection causes edematous skin erosions and hyperplasias pathologically characterized by large eosinophilic cytoplasmatic inclusions in the epithelial cells. Extensive necrosis in the lymphatic organs and the liver are also observed. In mice surviving the infection, diagnosis may be made by serology, while diagnosis of acute infection is based upon polymerase chain reaction, immunohistochemistry, and virus isolation.120 Today, the spontaneous disease is seldom in laboratory mice, although incidents have occurred, but major concern should be applied to biological materials of insecure origin.121,120

In rabbits, several poxviruses are known, i.e., myxoma, fibroma, and rabbit poxviruses. Of major concern is the myxoma virus, the cause of myxomatosis. In laboratory rabbits, this is a severe disease in which edema of the eyelids is the most dominant symptom. It may occur in a peracute version, which kills the rabbits within 1 week, or in an acute version with maybe 2 weeks of survival after edema also has developed around the anal, genital, oral, and nasal openings. Lethargy, hemorrhages, and convulsions occur just prior to death. The disease may be diagnosed by symptoms, but in countries in which the infection is under legal control, the diagnosis should be confirmed by virus isolation. Current screening may be performed by serology. Outbreaks in laboratory colonies are rare, as it mainly spreads through insects, but it should be kept in mind that the disease is endemic in the wild population of lagomorphs in Europe, North and South America, and Australia, even though it is under legal control in many countries.

0 0

Post a comment