Simian varicella in old world monkeys

Abstract

Simian varicella virus (SVV) causes a natural erythematous disease in Old World monkeys and is responsible for simian varicella epizootics that occur sporadically in facilities housing nonhuman primates. This review summarizes the biology of SVV and simian varicella as a veterinary disease of nonhuman primates. SVV is closely related to varicella-zoster virus, the causative agent of human varicella and herpes zoster. Clinical signs of simian varicella include fever, vesicular skin rash, and hepatitis. Simian varicella may range from a mild infection to a severe and life-threatening disease, and epizootics may have high morbidity and mortality rates. SVV establishes a lifelong latent infection in neural ganglia of animals in which the primary disease resolves, and the virus may reactivate later in life to cause a secondary disease corresponding to herpes zoster. Prompt diagnosis is important for control and prevention of epizootics. Antiviral treatment for simian varicella may be effective if administered early in the course of infection.

Figure 1.

SVV-infected Vero cells and the SVV genome. (A) Light microscopy of SVV cytopathic effect in a Vero cell monolayer (magnification, ×20). (B) Electron microscopy of a SVV-infected Vero cell. Note the SVV nucleocapsids (NC) within the cell nucleus (N) and degraded virions within cell vacuoles (V). Reprinted with kind permission by Springer Science and Business Media. (C) The 124.7-kb SVV genome includes a long (L) component with a unique long region (UL) bracketed by 64-bp repeat sequences (open rectangles) and a short (S) component composed of a unique short (US) sequence bracketed by 7.5-kb internal and terminal inverted repeats (IRS and TRS, respectively). The invertable terminal repeat element (TRE) at the left end of the genome is indicated.

Figure 2.

Pathogenesis and clinical course of simian varicella.

Figure 3.

Simian varicella skin rash. (A) Typical skin vesicles observed in a monkey with uncomplicated simian varicella. Reprinted with permission from Blackwell Publishing. (B) Hemorrhagic skin rash in a monkey with severe varicella. Photograph provided by the Washington National Primate Research Center.

Figure 3.

Simian varicella skin rash. (A) Typical skin vesicles observed in a monkey with uncomplicated simian varicella. Reprinted with permission from Blackwell Publishing. (B) Hemorrhagic skin rash in a monkey with severe varicella. Photograph provided by the Washington National Primate Research Center.