A Silent Enzootic of an Orthopoxvirus in Ghana, West Africa: Evidence for Multi-Species Involvement in the Absence of Widespread Human Disease

Mary G Reynolds,J Jeffrey Root,Inger K Damon,Cody Clemmons,Kevin Karem,Richard Suu-Ire,Jason Abel,Anna Likos,Victoria A Olson,Darin S Carroll,Mubarak O Kwasi,Joel M Montgomery,Christine Hughes,Russell Regnery,Zach Braden,Jack Galley

doi:10.4269/ajtmh.2010.09-0716

Abstract

Human monkeypox has never been reported in Ghana, but rodents captured in forested areas of southern Ghana were the source of the monkeypox virus introduced into the United States in 2003. Subsequent to the outbreak in the United States, 204 animals were collected from two commercial trapping sites in Ghana. Animal tissues were examined for the presence of orthopoxvirus (OPXV) DNA using a real-time polymerase chain reaction, and sera were assayed for antibodies against OPXV. Animals from five genera (Cricetomys, Graphiurus, Funiscirus, and Heliosciurus) had antibodies against OPXV, and three genera (Cricetomys, Graphiurus, and Xerus) had evidence of OPXV DNA in tissues. Additionally, 172 persons living near the trapping sites were interviewed regarding risk factors for OPXV exposure, and their sera were analyzed. Fifty-three percent had IgG against OPXV; none had IgM. Our findings suggest that several species of forest-dwelling rodents from Ghana are susceptible to naturally occurring OPXV infection, and that persons living near forests may have low-level or indirect exposure to OPXV-infected animals, possibly resulting in sub-clinical infections.

Highlights

IntroductionThe first case of human monkeypox (MPX) was identified in 1970 in the Basankusu District of the Democratic Republic of the Congo (former Zaire) during the intensification phase of the smallpox eradication campaign.[1] In that same year, five additional MPX cases were reported in west Africa, four in Liberia and one in Sierra Leone.[2,3] during the subsequent 13 years, only 11 of the 155 MPX cases identified in Africa were reported from west Africa countries (Côte d’Ivoire, Liberia, Nigeria, Sierra Leone);[4] most cases occurred in the Democratic Republic of the Congo
The first case of human monkeypox (MPX) was identified in 1970 in the Basankusu District of the Democratic Republic of the Congo during the intensification phase of the smallpox eradication campaign.[1]
During the subsequent 13 years, only 11 of the 155 MPX cases identified in Africa were reported from west Africa countries (Côte d’Ivoire, Liberia, Nigeria, Sierra Leone);[4] most cases occurred in the Democratic Republic of the Congo

Summary

Introduction

The first case of human monkeypox (MPX) was identified in 1970 in the Basankusu District of the Democratic Republic of the Congo (former Zaire) during the intensification phase of the smallpox eradication campaign.[1] In that same year, five additional MPX cases were reported in west Africa, four in Liberia and one in Sierra Leone.[2,3] during the subsequent 13 years, only 11 of the 155 MPX cases identified in Africa were reported from west Africa countries (Côte d’Ivoire, Liberia, Nigeria, Sierra Leone);[4] most cases occurred in the Democratic Republic of the Congo. The natural cycle of MPX within its native range is poorly understood, as is the route of transmission to humans in the tropical forest setting. The only MPX virus isolated from a wild-caught mammal was obtained from a single moribund rope squirrel (Funisciurus anerythrus) collected during an outbreak investigation in Zaire.[5] Primary human (and nonhuman primate) infections are hypothesized to result from contact with an infected sylvan animal, this reservoir host species is currently unknown

Methods

Results

Conclusion