Human Papillomavirus Epidemiology in Nigeria

BACKGROUND: Cervical cancer, caused by persistent infection with approximately 15-20 genotypes of carcinogenic human papillomavirus (HPV) infection, is the second leading cause of female cancer. Cytology (Pap smears) and the new HPV vaccines are not widely available in poor regions. Immediate treatment of HPV-infected older women by cryotherapy might have greater impact.

Although the same HPV types cause cervical cancer everywhere, and the same stages (infection, persistence vs. clearance, progression to precancer, and invasion) typify cervical carcinogenesis, the patterns of age-specific prevalence of HPV vary widely. These patterns are important for secondary prevention strategies relying on HPV DNA testing.

In many regions, including the US, HPV infections appear as classical sexually-transmitted agents, with peak cervical DNA prevalence at young ages (approximately 20) and low prevalence at older ages. However, in Nigeria, HPV prevalence is high (greater than or equal to 15%) at all ages according to the one study performed in urban Ibadan by Franceschi s group at IARC (n=932 women). This pattern is very uncommon. High prevalence at all ages would preclude use of HPV testing in low-cost strategies, due to poor positive predictive value. One possibly relevant element is the marital structure in Nigeria; a man often has multiple wives.

OBJECTIVES: The major objectives are: 1) To estimate age-specific HPV prevalences in Irun, Nigeria; 2) To investigate epidemiologic risk factors for HPV and cervical intraepithelial neoplasia in this population; 3) To examine the performance of screening options; 4) To assess the correlation of HPV among co-wives, comparing households with multiple wives with those with single wives; and 5) To validate the performance of rapid HPV, an inexpensive HPV test designed for public-sector use in settings like Irun.

ELIGIBILITY: All non-pregnant women aged 15+, without hysterectomy, will be eligible if they can provide written informed consent. Unmarried women less than 21 will be enrolled only with parental consent. Sexually active women will be examined and asked for cervical specimens; self-reported virginal women will be asked for a 10-ml blood sample only.

DESIGN: This is a cross-sectional screening study of 1500 women in Irun, a Nigerian village. Unlike the IARC study, we will incorporate cytology, visual inspection, and colposcopic biopsy of women that test positive by any of the three screening tests. We will determine whether HPV infection at various ages is related to risk of cervical abnormalities. The analyses will include descriptive trend data, multivariable modeling of HPV determinants, and clinical epidemiologic analysis of relative screening test performance in detecting cervical neoplasia.