Seroreactivity to Chikungunya and West Nile Viruses in Rwandan Blood Donors.

Introduction: Chikungunya virus (CHIKV) and West Nile virus (WNV) have previously been reported from several African countries, including those bordering Rwanda where they may have originated. However, there have been no serosurveillance reports from Rwanda regarding these two viral pathogens. In this article, we present the first study of immunoglobulin G (IgG) seroreactivity of CHIKV and WNV in Rwandan blood donor samples. Methods: Blood donors from Rwanda (n = 874) and Sweden (n = 199) were tested for IgG reactivity against CHIKV, using an in-house enzyme-linked immunosorbent assay with the E1 envelope protein fused with p62 as antigen, and against WNV using a commercial kit. Data on mosquito distribution were obtained from the 2012 assessment of yellow fever virus circulation in Rwanda. Results: Seroreactivity to CHIKV was high in Rwanda (63.0%), when compared with Swedish donors, where only 8.5% were IgG positive. However, a cross-reactivity to O'nyong'nyong virus in neutralization test was noted in Rwandan donors. No significant difference in WNV seroreactivity was found (10.4% for Rwandan and 14.1% for Swedish donors). The relatively high seroreactivity to WNV among Swedish donors could partly be explained by cross-reactivity with tick-borne encephalitis virus prevalent in Sweden. Donors from the Eastern Province of Rwanda had the highest IgG reactivity to the two investigated viruses (86.7% for CHIKV and 33.3% for WNV). Five genera of mosquitoes were found in Rwanda where Culex was the most common (82.5%). The vector of CHIKV, Aedes, accounted for 9.6% of mosquitoes and this species was most commonly found in the Eastern Province. Conclusions: Our results showed high seroreactivity to CHIKV in Rwandan donors. The highest IgG reactivity to CHIKV, and to WNV, was found in the Eastern Province, the area reporting the highest number of mosquito vectors for these two viruses. Infection control by eliminating mosquito-breeding sites in population-dense areas is recommended, especially in eastern Rwanda.

Seroprevalence of Zika virus and Rubella virus IgG among blood donors in Rwanda and in Sweden.

Seroprevalence studies provide information on the susceptibility to infection of certain populations, including women of childbearing age. Such data from Central Africa are scarce regarding two viruses that cause congenital infections: Zika virus (ZIKV), an emerging mosquito-borne infection, and Rubella virus (RuV), a vaccine-preventable infection. We report on the seroprevalence of both ZIKV and RuV from Rwanda, a country without any known cases of ZIKV, but bordering Uganda where this virus was isolated in 1947. Anti-ZIKV-specific and anti-RuV-specific immunoglobulin G (IgG) antibodies were analyzed by enzyme-linked immunosorbent assay (ELISA) in serum samples from 874 Rwandan and 215 Swedish blood donors. Samples positive for IgG antibodies against ZIKV were examined for viral RNA using real-time reverse transcription polymerase chain reaction (RT-qPCR). The seroprevalence of ZIKV IgG in Rwanda was 1.4% (12/874), of which the predominance of positive findings came from the Southeastern region. All anti-ZIKV IgG-positive samples were PCR-negative. Among 297 female blood donors of childbearing age, 295 (99.3%) were seronegative and thus susceptible to ZIKV. All Swedish blood donors were IgG-negative to ZIKV. In contrast, blood donors from both countries showed high seroprevalence of IgG to RuV: 91.2% for Rwandan and 92.1% for Swedish donors. Only 10.5% (31/294) of female donors of childbearing age from Rwanda were seronegative for RuV. In Rwanda, seroprevalence for ZIKV IgG antibodies was low, but high for RuV. Hence, women of childbearing age were susceptible to ZIKV. These data may be of value for decision-making regarding prophylactic measures.

Measles seroprevalence, outbreaks, and vaccine coverage in Rwanda.

BACKGROUND: Measles outbreaks are reported after insufficient vaccine coverage, especially in countries recovering from natural disaster or conflict. We compared seroprevalence to measles in blood donors in Rwanda and Sweden and explored distribution of active cases of measles and vaccine coverage in Rwanda. METHODS: 516 Rwandan and 215 Swedish blood donors were assayed for measles-specific immunoglobulin G (IgG) by enzyme-linked immunosorbent assay (ELISA). Data on vaccine coverage and acute cases in Rwanda from 1980 to 2014 were collected, and IgM on serum samples and polymerase chain reaction (PCR) on nasopharyngeal (NPH) swabs from suspected measles cases during 2010-2011 were analysed. RESULTS: The seroprevalence of measles IgG was significantly higher in Swedish blood donors (92.6%; 95% CI: 89.1-96.1%) compared to Rwandan subjects (71.5%; 95% CI: 67.6-75.4%) and more pronounced <35 years of age. The OD values were significantly lower in the Rwandan blood donors as compared to Swedish subjects (p < 0.00001). However, effective measles vaccine coverage was concomitant with decrease in measles cases in Rwanda, with the exception of an outbreak in 1995 following the 1994 genocide. 76/544 serum samples were IgM positive and 21/31 NPH swabs were PCR positive for measles, determined by sequencing to be of genotype B3. CONCLUSIONS: Measles seroprevalence was lower in Rwandan blood donors compared to Swedish subjects. Despite this, the number of reported measles cases in Rwanda rapidly decreased during the study period, concomitant with increased vaccine coverage. Taken together, the circulation of measles was limited in Rwanda and vaccine coverage was favourable, but seroprevalence and IgG levels were low especially in younger age groups.