Sero-prevalence of rubella-specific antibodies in pregnant women attending antenatal care in Maiduguri, north-eastern Nigeria

Abstract

Context: Rubella is a disease caused by a virus –rubella virus. Major obstetrics concerns are profound effects of the virus on developing fetuses, which may result in multiple congenital malformations. Although vaccination has reduced the incidence of rubella virus substantially; the world health organization (WHO) estimated that more than 100,000 cases of congenital rubella syndrome occur each year worldwide, most of them in developing countries. Diagnosis of rubella cannot be made on clinical grounds alone due to lack of specific symptoms or signs that are unique to the disease. Laboratory confirmation of suspected cases is done based on the detection of the presence of immunoglobulin M (IgM) during the acute illness or a significant rise in rubella – immunoglobulin G (IgG) antibody titres in the serum of previously infected individuals. Methodology: This is a descriptive cross-sectional study conducted at the antenatal clinic of the Department of Obstetrics and Gynaecology of the University of Maiduguri Teaching Hospital (UMTH), Maiduguri, Borno State, North-Eastern Nigeria. Eligible women who presented for booking for antenatal care at the hospital were recruited. Their bio-data, educational status, and history of vaccination with measles and previous obstetrics outcomes were obtained. Five milliliters of venous blood was taken and the serum obtained from the sample was analyzed for anti-rubella IgG antibodies. The samples that were negative for IgG were tested for IgM antibodies. Data obtained analyzed using the statistical package for social science SPSS v16.0.0 (Sept 13, 2007) Inc, Illinois, USA. Results: There were 459 pregnant women who consented and participated in the study. Their age range is 17-43 years (mean= 25.8±5.3). There were 280 (61.0%) patients who were multiparous (mean=3.5±2.1) and women with secondary education accounted for 39.4%. Four hundred twenty-one women (91.7%) women tested positive for rubella-specific IgG antibodies, and of the remaining 38 women, 6 (15.8%) were positive for IgM rubella-specific antibody. Most of the patients (98.1%) with positive IgG had serum titers in the range of 51-150U/mL. All the patients with positive IgM antibodies were followed up till birth, all the pregnancies were carried to term and none of the neonates was found to have any congenital malformation. None of the socio-demographic characteristics were found to be significantly associated with presence of IgG antibodies. Past history of abortions and congenital cataracts were significantly associated with IgG sero-positivity. Conclusion: The sero-prevalence of anti-rubella IgG sero-positivity is high in Maiduguri and this indicates high herd immunity. The number of pregnant women requiring rubella vaccination postpartum in also large. It is recommended that inclusion of rubella vaccination in the National programme on Immunization protocol will be cost effective in the control of rubella and CRS.