Congenital infection and congenital cataract in Tanzania: A case control study

Background: Cataract is the commonest cause of childhood blindness in sub Saharan Africa (SSA). The significance of congenital rubella and human cytomegalovirus (HCMV) infection in the etiology is not known. Objectives: We aimed to investigate prevalence of both viruses in cases of congenital cataract and controls. Methods: Lens tissue was collected (from cases), blood and saliva from cases and controls. Using ELISA, we tested blood samples for rubella and cytomegalovirus IgM. Quantitative polymerase chain reaction (qPCR) was also used for detection of the viruses. Results: Cytomegalovirus was detected using qPCR in 72.9% saliva specimens of cases compared to 38.5% of controls (P = 0.0001). Cytomegalovirus IgM was also detected in 10.8% blood specimens of cases and only 1.5% control (P = 0.01). Rubella IgM was detected in 13.8% blood specimens of cases and only 3.1% controls (P = 0.01). In lens aspirates of cases, 12.7% were HCMV positive and 11.1% were rubella positive by qPCR. Cases had lower birth weights (mean = 2.8 kg) than controls (mean = 3.2 kg), independent of viral status (P = 0.004). Conclusions: Although most of the children in the study presented too late to be sure that infection was congenital, our study strongly suggests that HCMV and rubella infection appear important causes of congenital cataract in Tanzania hence virology testing of infantile cataract cases may be useful in assessing effectiveness of immunization programs as they are established throughout SSA.