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The pox in the North American backyard: Volepox virus pathogenesis in California mice (Peromyscus californicus)
Nadia F Gallardo-Romero1, Clifton P Drew, Sonja L Weiss
1Poxvirus and Rabies Branch, Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America. hfa5@cdc.gov
Abstract:
Volepox virus (VPXV) was first isolated in 1985 from a hind foot scab of an otherwise healthy California vole (Microtus californicus). Subsequent surveys in San Mateo County, CA, revealed serological evidence suggesting that VPXV is endemic to this area, and a second viral isolate from a Pinyon mouse (Peromyscus truei) was collected in 1988. Since then, few studies have been conducted regarding the ecology, pathology, and pathogenicity of VPXV, and its prevalence and role as a potential zoonotic agent remain unknown. To increase our understanding of VPXV disease progression, we challenged 24 California mice (Peromyscus californicus) intranasally with 1.6 × 10(3) PFU of purified VPXV. By day five post infection (pi) we observed decreased activity level, conjunctivitis, ruffled hair, skin lesions, facial edema, and crusty noses. A mortality rate of 54% was noted by day eight pi. In addition, internal organ necrosis and hemorrhages were observed during necropsy of deceased or euthanized animals. Viral loads in tissues (brain, gonad, kidney, liver, lung, spleen, submandibular lymph node, and adrenal gland), bodily secretions (saliva, and tears), and excretions (urine, and/or feces) were evaluated and compared using real time-PCR and tissue culture. Viral loads measured as high as 2 × 10(9) PFU/mL in some organs. Our results suggest that VPXV can cause extreme morbidity and mortality within rodent populations sympatric with the known VPXV reservoirs.
Insights
Volepox virus (VPXV) causes severe disease in California mice, leading to high mortality and widespread viral infection. This study highlights VPXV
Area of Science:
- Virology
- Pathology
- Ecology
Background:
- Volepox virus (VPXV) was first isolated in 1985, with limited subsequent research on its ecology, pathology, and zoonotic potential.
- VPXV is suspected to be endemic in California voles (Microtus californicus) and Pinyon mice (Peromyscus truei).
Purpose of the Study:
- To investigate the disease progression, pathogenicity, and viral dissemination of Volepox virus (VPXV) in a laboratory setting.
- To assess the impact of VPXV infection on California mice (Peromyscus californicus).
Main Methods:
- Intranasal inoculation of 24 California mice with purified VPXV (1.6 × 10(3) PFU).
- Clinical observation for signs of disease, mortality assessment up to day eight post-infection (pi).
- Necropsy and histopathological examination of internal organs.
- Quantification of viral loads in various tissues, secretions, and excretions using real-time PCR and tissue culture.
Main Results:
- VPXV infection induced significant clinical signs by day five pi, including decreased activity, conjunctivitis, ruffled fur, skin lesions, facial edema, and nasal crusting.
- A high mortality rate of 54% was observed by day eight pi.
- Necropsy revealed internal organ necrosis and hemorrhages; viral loads reached up to 2 × 10(9) PFU/mL in certain tissues.
Conclusions:
- VPXV infection leads to severe morbidity and mortality in susceptible rodent populations.
- The virus disseminates widely throughout the body, affecting multiple organs, secretions, and excretions.
- Further research is warranted to understand the ecological role and zoonotic implications of VPXV.
