Isolation of poxvirus from an African Rodent

Area of Science:

• Virology
• Zoonotic Diseases
• Comparative Pathology

Background:

• Poxviruses, including smallpox (variola) virus, pose significant public health threats.
• Understanding the diversity of poxviruses in animal reservoirs is crucial for disease surveillance and control.
• Previous studies have identified various animal poxviruses with varying degrees of similarity to human pathogens.

Purpose of the Study:

• To characterize a newly isolated poxvirus from a wild gerbil in Africa.
• To compare the biological and pathological properties of this isolate with known poxviruses, particularly variola and vaccinia subgroups.
• To investigate the potential role of this gerbil poxvirus in the epidemiology of human smallpox.

Main Methods:

• Isolation and characterization of the poxvirus from a wild gerbil (Tatera kempii).
• Electron microscopy for viral morphology assessment.
• Serological testing for cross-reactivity with known poxviruses.
• In vitro studies including pock morphology on chorioallantoic membrane, ceiling temperature determination, and cytopathic effect in tissue culture.
• In vivo studies involving inoculation into mice and rhesus monkeys.

Main Results:

• A poxvirus was isolated from a gerbil during a human smallpox epidemic.
• Electron microscopy and serology indicated the virus belongs to the vaccinia subgroup.
• The isolate exhibited distinct characteristics differentiating it from ectromelia, rabbitpox, vaccinia, monkeypox, and cowpox viruses.
• Notably, it shared features with variola minor virus, including a ceiling temperature of 38°C and failure to grow in rabbit skin.
• In rhesus monkeys, the virus caused fever without eruption but induced seroconversion and protection against monkeypox virus challenge.

Conclusions:

• The gerbil poxvirus isolate represents a distinct member of the poxvirus family with unique biological properties.
• Its similarities to variola minor virus and its ability to induce protective immunity against monkeypox virus highlight its epidemiological significance.
• The findings support the hypothesis that inapparent infections in animal reservoirs, like gerbils, may contribute to the long-term survival of variola virus, alongside human-to-human transmission.