Orthopoxvirus variola infection of Cynomys ludovicianus (North American black tailed prairie dog)

Abstract

Since the eradication of Smallpox, researchers have attempted to study Orthopoxvirus pathogenesis and immunity in animal models in order to correlate results human smallpox. A solely human pathogen, Orthopoxvirus variola fails to produce authentic smallpox illness in any other animal species tested to date. In 2003, an outbreak in the USA of Orthopoxvirus monkeypox, revealed the susceptibility of the North American black-tailed prairie dog (Cynomys ludovicianus) to infection and fulminate disease. Prairie dogs infected with Orthopoxvirus monkeypox present with a clinical scenario similar to ordinary smallpox, including prodrome, rash, and high mortality. This study examines if Black-tailed prairie dogs can become infected with O. variola and serve as a surrogate model for the study of human smallpox disease. Substantive evidence of infection is found in immunological seroconversion of animals to either intranasal or intradermal challenges with O. variola, but in the absence of overt illness.

Keywords: Animal model; Immunity; Infection; Orthopoxvirus; Prairie dog; Smallpox; Variola.

Fig. 1

Summary of clinical pathogenesis and stages of illness of smallpox in humans, and monkeypox in humans, prairie dogs and rhesus maquaces.

Fig. 2

Photos of inoculation sites day 7 post inoculation (a) intranasally and (b) intradermally.

Fig. 3

Weights of animals (in grams) post challenge, measured every 3 days.

Fig. 4

ELISA of anti-Orthopoxvirus antibody in animal sera. Values are reported as post challenge (day 21) minus pre challenge (day 0) absorbance at 450 nm.