A Cross-Sectional Serosurvey of Anti-Orthopoxvirus Antibodies in Central and Western Africa.

Chantal Akoua-Koffi,Lidewij Wiersma,Andreas Nitsche,Arsène Mossoun,Siv Leendertz,Daniel Stern,Stomy Karhemere,Livia Schrick,Fabian Leendertz,Emmanuel Couacy-Hymann,Jean-Jacques Muyembe-Tamfum,Grit Schubert,Dennis Theophil,Maude Pauly,Etile Anoh

doi:10.3390/v9100278

Abstract

Since the eradication of smallpox and the subsequent discontinuation of the worldwide smallpox vaccination program, other Orthopoxviruses beside Variola virus have been increasingly representing a risk to human health. To investigate the extent of natural contact with Orthopoxviruses and possible demographic risk factors for such an exposure, we performed a cross-sectional serosurvey of anti-Orthopoxvirus IgG antibodies in West and Central Africa. To this end, people living in forest regions in Côte d’Ivoire (CIV, n = 737) and the Democratic Republic of the Congo (COD, n = 267) were assigned into groups according to their likely smallpox vaccination status. The overall prevalence of anti-Orthopoxvirus antibodies was 51% in CIV and 60% in COD. High rates of seropositivity among the vaccinated part of the population (80% in CIV; 96% COD) indicated a long-lasting post vaccination immune response. In non-vaccinated participants, seroprevalences of 19% (CIV) and 26% (COD) indicated regular contact with Orthopoxviruses. Multivariate logistic regression revealed that the antibody level in the vaccinated part of the population was higher in COD than in CIV, increased with age and was slightly higher in females than males. In the unvaccinated part of the population none of these factors influenced antibody level significantly. In conclusion, our results confirm expectedly high anti-Orthopoxvirus seroprevalences in previously smallpox-vaccinated people living in CIV and the COD but more unexpectedly imply regular contact with Orthopoxviruses both in Western and Central Africa, even in the absence of recognized outbreaks.

Highlights

The Orthopoxvirus (OPV) genus comprises several viruses pathogenic to humans, like Cowpox virus (CPXV), Vaccinia virus (VACV), Monkeypox virus (MPXV), and Variola virus (VARV) [1]
We found that the anti-OPV seroprevalence in smallpox-vaccinated participants in both other studies employing haemagglutination-inhibition tests describe lower overall seroprevalences in countries was high with 80% and 96% in CIV and COD, respectively
We found that the anti-OPV seroprevalence in smallpox-vaccinated participants in both countries was high with 80% and 96% in CIV and COD, respectively

Summary

Introduction

The Orthopoxvirus (OPV) genus comprises several viruses pathogenic to humans, like Cowpox virus (CPXV), Vaccinia virus (VACV), Monkeypox virus (MPXV), and Variola virus (VARV) [1]. In Europe, increasing numbers of documented infections with CPXV are being observed [6,7], while VACV-like viruses cause infections in South America [8] and MPXV cause infections in Africa [9]. CPXV is transmitted to humans mainly by direct contact to rodents or cats, and in most cases CPXV causes a self-limiting skin disease. In the era of smallpox vaccination, MPXV was not recognized as a discrete entity until the 1970s [12] Rodents, such as squirrels of the Funisciurus and Heliociurus genera, are thought to be the reservoir of the virus and the likely source of human disease [13,14]. The ecological factors that influence host distribution and viral emergence are not completely understood [11,16]

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Conclusion