Cytomegalovirus (CMV) is a frequent cause of congenital infection and a leading nongenetic cause of permanent congenital or early-onset hearing loss (PCEHL) in children.1,2 Although limited data suggest high prevalence of congenital CMV (cCMV) infection in developing countries with high maternal CMV seroprevalence, the burden of disease and natural history of cCMV infection, especially in sub-Saharan Africa, have not been well defined.1,3–5 Additionally, the role of cCMV in PCEHL in the African continent has not been examined, although infants with microcephaly have been reported to be significantly at risk for PCEHL in Nigeria.6 Early identification of infants with cCMV allows for prompt detection of children at risk for PCEHL who require appropriate intervention during critical stages of language development.1,2 Real-time polymerase chain reaction (PCR) testing of newborn saliva has been shown to be highly specific and sensitive for detecting CMV-infected infants.7,8 We therefore conducted a pilot study to determine the prevalence of cCMV in an inner-city community in Lagos, Nigeria, with a previously reported high occurrence of PCEHL.9
Infants were enrolled in the study by convenient sampling of neonates on admission between November 2012 and April 2013 at Island Maternity Hospital (IMH) and Massey Children’s Hospital (MCH) in Lagos, Nigeria, whose mothers gave consent to participate in the study. Demographic data and medical history were obtained from hospital records and ethical approval from the Lagos State Government Health Service Commission. Dried saliva swabs were collected, labeled with a unique ID number and transported to the University of Alabama at Birmingham for testing by real-time PCR for CMV without the DNA extraction step as described.7,8 A sample was considered positive if one or more international units (IU) per reaction was detected. The detection limit of this PCR assay was determined to be 116 IU/mL of the sample (1.72 ge/mL = 1 IU/mL) using the Acrometrix (Life Technologies, Grand Island, NY) CMV international standards. No follow-up visits were included, but parents were informed of the infant’s CMV status for further medical attention. HIV 1 and HIV 2 testing was routinely conducted during pregnancy using 2 rapid immunochromatographic screening test kits.9 Two negative or positive results are confirmatory for HIV status. Discordant results were resolved with enzyme-linked immunosorbent assay. Data were analyzed using SPSS statistical package version 21 (IBM Corp, Armonk, NY). To determine differences between infants with and without cCMV, we used a case-control sample in which infants with CMV were matched on the basis of gender to infants without CMV in the ratio of 1:10. Gender was selected as the matching criterion because of the potential confounding effect of the high frequency of glucose-6-phosphate dehydrogenase deficiency in male infants in the study population. The controls were selected from infants with the closest dates of birth from the same hospital. Maternal age, ethnicity, gravidity, parity, mode of delivery, HIV status, multiple gestation, gestational age, birth weight, presence of neonatal jaundice and admission status were compared between CMV-infected and CMV-uninfected infants. Statistical significance was determined by Pearson χ2 test or Fisher exact for categorical variables and student t test for continuous variables.
Of the 263 infants tested, 10 (6 females and 4 males) were CMV positive, amounting to a prevalence rate of 3.8% (95% confidence interval: 2.1–6.9%). The prevalence of cCMV was not significantly different between the 2 hospitals: 3.4% (5 of 149) versus 4.4% (5 of 114). The characteristics of CMV-infected newborns are shown in Table 1. Mean age of mothers with CMV-infected babies was 29.7 ± 6.1 years (IMH: 30.2 ± 8.04; MCH: 29.2 ± 4.38 years). Mean gestational age for CMV-infected infants was 35.9 ± 4.0 weeks (IMH: 35.0 ± 3.74; MCH: 37.0 ± 3.94 weeks), with a mean birth weight of 2.2 ± 1.3 kg (IMH: 2.39 ± 1.30; MCH: 3.23 ± 1.06 kg). Of the infected children, 2 infants were symptomatic. Both infants had hepatosplenomegaly and bronchopneumonia, and 1 baby had neonatal jaundice also. Maternal HIV status was known for 162 infants including 8 congenitally infected children. The prevalence of maternal HIV infection was 4.9% (6 of 162), and none of the CMV-infected babies was born to a HIV-positive mother. There were no statistically significant differences between CMV-infected infants and their matched controls with respect to maternal age, ethnicity, gravidity, parity, gestational age, maternal HIV status and birth weight (see Table, Supplemental Digital Content 1, http://links.lww.com/INF/C19).
This study utilized a virologic assay that is reliable and convenient to identify CMV-infected newborns. By eliminating the requirement for DNA extraction, this PCR assay has significant cost savings also. The results from this population with near-universal seroimmunity demonstrated the high prevalence of cCMV and the feasibility of screening newborns by real-time PCR of dried-saliva swabs in resource-poor settings.
The prevalence of cCMV in this study falls within the reported range of 0.9% (Mexico) and 5.4% (Gambia) for developing countries but well over 0.5–0.7% reported in developed countries.1,3–5 Our findings are consistent with those reported in a recent study from Zambia in which cCMV, based on the detection of CMV DNA in saliva, urine or sera or on the detection of serum CMV-IgM antibodies, was detected in 3.8% (15 of 395) of neonatal admissions in the first 3 weeks in a population with high maternal HIV prevalence.3 A study from the Gambia reported significantly higher prevalence of cCMV (5.4%, 40 of 741), which was associated with active placental malarial infection.4 Although CMV seroprevalence was not determined as part of this study, a previous study among pregnant women in Lagos, Nigeria, showed that 97.2% were CMV-IgG positive.10 It is therefore likely that most women in our study were seroimmune before pregnancy.
High prevalence (2.9%, 22 of 748) of cCMV in HIV-exposed infants was also documented in a recent study from South Africa.5 Compared with findings from Zambia and South Africa, none of the HIV-exposed infants was CMV-infected in our study.3,5 In the Zambian study, the prevalence of cCMV was 11.4% and 2.1% among neonates born to HIV-infected and HIV-uninfected mothers, respectively.3 In Western Cape, South Africa, 2.9% of infants born to 748 HIV-infected mothers had cCMV.5 The prevalence of maternal HIV infection of 4.9% in our study population is consistent with previous data from this inner-city community.8 HIV-infection status was known for 162 mothers including 8 mothers with CMV-infected newborns, and none of the babies with cCMV was born to HIV-infected mothers. However, the number of women with HIV infection in this study is too small to determine the role of maternal HIV infection on intrauterine CMV transmission, and therefore, the association between cCMV and maternal HIV in this population merits further research.
There were no associations between congenital CMV and maternal age, parity, mode of delivery, gestational age, birth weight, gender and jaundice. A major limitation of this study is the small sample size and the use of convenience sampling. Thus, it is not clear whether these data are representative of cCMV prevalence in the population in Nigeria. Additionally, infected children were not followed to document long-term outcomes. Although the real-time PCR assay has been shown to be highly specific in previous studies in the United States, it is possible that the rate of false-positive PCR results could be higher in populations with concurrent maternal infections.7,8 Nevertheless, the findings of this study underscore the need for a prospective newborn CMV screening study with long-term follow-up to document the natural history and disease burden of cCMV in this population. In addition, the utility of the real-time PCR assay should be evaluated in larger studies in such populations. It is crucial to examine the role of cCMV among infants with congenital, early-onset/late-onset, fluctuating and progressive sensorineural hearing loss to develop evidence-based guidelines for intervention advocacy for at-risk infants. Overall, this pilot study and the follow-up research should fill an important epidemiologic gap in the study of cCMV infection in sub-Saharan Africa.
We thank the management of IMH and Massey Street Children’s Hospital, Lagos, Nigeria, for their support in facilitating access to the participants in this study.
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