Seroprevalence of some Arboviruses among Pregnant Women in Ibadan, Southwestern, Nigeria

To determine the seroprevalence of some arboviruses among pregnant women attending antenatal clinic in Ibadan, Nigeria. Sera of 36 ELISA anti-Zika virus immunoglobulin M (IgM)- and/or immunoglobulin G (IgG)-positive pregnant women attending antenatal clinic in 3 hospitals in Ibadan, Nigeria were screened for the presence of antibodies to Zika, yellow fever, dengue-1 and -2, Spondweni, West Nile, and chikungunya viruses using haemagglutination inhibition (HI). Overall, 22 (61.1%) of the 36 sera tested had antibodies to other tested arboviruses. All the sera which tested positive, had antibodies to at least two or more viruses, 4 (11.1%) tested positive to 6 of the viruses, 4 (11.1%) tested positive to 5 of the viruses, 1 (2.8%) to 4 of the viruses, 8 (22.2%) to 3 of the viruses, 5(13.9%) to only 2 of the viruses. Antibody to dengue-1 was observed in all positive sera. Antibodies to Zika, dengue-2 and chikungunya were observed in 55.6%, 38.9%, and 25%, respectively while antibodies to Spondweni, West Nile and yellow fever were detected in 22.2%, 13.9% and 11.1% respectively. Titre values observed ranged from 1:20 to 1:320. About 47% of participants had antibodies to Zika and 2 other arboviruses and 25% to Zika virus and 3 or more arboviruses. The presence of antibodies to these viruses suggests a persistence of infections in Ibadan. A low (11.1%) prevalence of antibodies to yellow fever virus was observed. Sera of 14 (38.9%) participants positive for anti-ZIKV IgM and/or IgG by NS-1 based ELISA were negative for Zika virus antibodies by HI. This study showed a high seroprevalence to arboviruses despite the low rate of reporting these infections in Nigeria. It also demonstrated a very low herd immunity to yellow fever despite Nigeria being in the category of countries recommended for vaccination in the Yellow Fever belt. Therefore, a large proportion of the community is at risk of yellow fever. These results further emphasize the importance of seroprevalence studies as an important tool in the assessment of disease burden, and epidemiology of arboviral diseases as well as herd immunity.