Human papillomavirus, coinfection with Schistosoma hematobium, and cervical neoplasia in rural Tanzania

Cervical cancer is the most common malignant tumor among women in Tanzania and other countries in tropical Africa. Genital schistosomiasis has been proposed as a possible cofactor in the genesis of this malignant disease that might contribute to its high incidence in regions where bilharzias is endemic. One hundred nine Tanzanian patients from an area with endemic bilharzias who were transferred to a gynecologic out-patient clinic were age-matched with 109 German controls. In patients and controls, separate samples were taken for cytologic assessment and human papillomavirus (HPV) DNA detection using the Hybrid Capture 2 assay (HC2) and PCR (GP5+/6 +). Samples that tested positive for HPV DNA with general primers were re-tested with HPV type-specific primers. After application of 3% acetic acid, punch biopsies were taken from any cervical lesion. Patients were interviewed for recent symptoms or clinical history suggestive of bilharzias. Urine samples from all patients were examined for the presence of schistosoma hematobium ova. Additionally six Tanzanian patients with invasive cervical cancer were included for separate analysis. Patients and controls had an identical prevalence of HPV-DNA (21.5%) using HC2. Based on PCR results with general primers, the corresponding prevalence was 34.5% for Tanzanian cases and 26.9% for German controls. A history suggestive of bilharzias and/or active schistosomiasis were associated with a significantly increased risk for infection with high-risk HPV types. We conclude that infection with Schistosoma hematobium seems to favor persistent genital HPV infection either by traumatizing the genital epithelium and/or by local immunosuppression.