First Detection of Antibodies Specific to Crimean-Congo Hemorrhagic Fever Virus in Rural Populations of Gabon

Abstract

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease with a mortality rate reaching up to 40% in humans. Currently, CCHF affects three continents: Asia, Europe, and Africa. An increase in confirmed cases in Africa has been observed since 2000. In Central Africa, several countries have reported the circulation of CCHV virus (CCHFV). However, in Gabon, there is a lack of recent data on the circulation of the virus in the Gabonese population. To provide an overview of the epidemiological situation in Gabon, we tested 3,081 human serum samples collected between 2005 and 2008 in villages throughout the country for anti-CCHFV antibodies. Using a double-antigen ELISA kit, our study found 15/3,081 samples positive for CCHFV. These positive samples were also tested using the Blackbox CCHFV IgG kit and the Luminex technique. These analyses confirmed seven and four positives for the Blackbox CCHFV IgG kit and the Luminex technique, respectively. This study suggests low circulation of CCHFV in the rural human population of Gabon. Competent authorities must survey CCHFV to identify and prevent clinical cases in the human population.

Figure 1.

Distribution of sampling collecting sites. Villages with positive and negative samples are indicated by red and green dots, respectively.

Figure 2.

Tests and results of the study.

Figure 3.

Seroneutralization assays using the Crimean-Congo hemorrhagic fever virus (CCHFV) transcription- and entry-competent virus-like particle (tc-VLP) system or vesicular stomatitis virus G protein (VSV-G)-pseudotyped lentiviruses on selected ELISA samples. (A) ELISA-positive and -negative serum samples or nonexposed human control sera diluted 1/50 were incubated with CCHFV tc-VLPs expressing nanoluciferase prior to infection of Huh7.5 cells stably expressing firefly luciferase. Luminescence was read 24 hours postinfection. Results were normalized to the IgG control (black dot), and an anti-Gc neutralizing antibody (red dot) was used as a positive control. Data represent the mean of two independent experiments performed in technical triplicate. (B) The same procedure as that described for panel A was performed using a VSV-G-pseudotyped lentivirus-based neutralization assay. (C) The C39 serum sample was serially diluted (2-fold) from 1/200 to 1/25, and the same procedure as that described for panels A and B was performed. The mean and standard deviation of results of one experiment performed in technical triplicate are shown. Statistical significance was analyzed using a two-way analysis of variance with Dunnett’s multiple comparison test (*P <0.05; **P <0.01).