An outbreak of pox disease in Carnivora of the family Felidae occurred in the Moscow Zoo. Two forms of the disease were found: (1) fatal, fulminant pulmonary without skin lesions and (2) dermal with rash. The severity of the dermal form varied from subclinical to lethal. The pulmonary form was characterized by pneumonia and exudative pleuritis, and large concentrations of virus were observed in the lungs and exudate. In addition to Carnivora of the family Felidae, two giant anteaters had a severe form of the disease (dermal with hemorrhages) and died. The agent of the outbreak appeared to be very closely related to cowpox virus; however, pocks developed at a lower temperature than do those that result from infection with cowpox virus. Strains isolated from sick animals were identical to the virus previously isolated from an outbreak of pox among elephants and okapi. The most probable sources of infection were rats that were fed to some of the animals. During the outbreak, a female attendant at the zoo became infected.

A new poxvirus was isolated in 1974 from the kidney of a wild big gerbil (Rhombomys opimus) caught in Turkmenia, where these gerbils are wide-spread. The virus resembles cowpox virus and is markedly different from the virus of infectious ectromelia, the best-known poxvirus of rodents. The new virus is apparently identical to other poxvirus isolates made from white rats and Felidae in the Moscow Zoo. Experimental inoculation of the natural hosts--big gerbils and yellow susliks (Citellus fulvus)--produced a severe infection with a high mortality rate. Trnasmission of virus to uninoculated cage mates was shown to occur. Virus persisted in convalescent animals and was present in urine 3 weeks after inoculation and in kidney and testis for at least 5 weeks after inoculation. The role of rodents as natural hosts of poxviruses is discussed.

Monkeypox virus cloning and isolation of the so-called ‘white’ clones from white pocks which this virus forms on the chorioallantoic membrane (CAM) were carried out. The isolated clones were stable and differed considerably from the parental strain. By their properties, they were identical to whitepox viruses formerly isolated from wildlife monkeys and rodents in Equatorial Africa. Besides stable ‘white’ clones, a number of virus cultures in the process of cloning were obtained which differed in quantitative content of virions, forming on CAM white pocks and pocks with hemorrhages. It appeared that the properties of the viral population as a whole (reaction type on rabbit skin, hemagglutination activity, etc.) depended on the rate of virions produced with different characteristics.

The clinical picture of a smallpox-like generalized infection in a gorilla which became sick on the 14th day fter its arrival at the Moscow Zoo is described. The causative agent of the disease was isolated and found to be a virus of the herpes group with properties resembling those of varicella-zoster virus. The evidence presented calls for a careful attitude toward reports on the pox nature of vesicular diseases in monkeys in cases which have not been confirmed virologically.

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