How does the prevalence and severity of schistosomiasis (bilharzia) vary by age?

Updated: Jun 11, 2020
  • Author: Shadab Hussain Ahmed, MD, AAHIVS, FACP, FIDSA; Chief Editor: Michael Stuart Bronze, MD  more...
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The prevalence and severity of schistosomal infections vary with age. Children and adolescents are infected most often and are infested most heavily. Infection rates and severity may vary with gender-specific activity at all ages. (Congenital infection has been defined; Schistosomiasis has been detected in the placenta and newborns have been diagnosed with the disease, thus confirming congenital infection. [6] ) [30]

Globally, infections peak in individuals aged 10-19 years. In some areas, the prevalence in this group may approach 100%.

In persons older than age 19 years living in endemic areas, the prevalence of active infection and egg counts slowly declines. (End-stage complications may persist or worsen.) This decline in active infection may reflect that individuals have an increasing host immune response or a decreasing exposure to contaminated water as they age. Reinfection, particularly after high exposure, is possible.

Age distribution differs somewhat in infected travelers, with young adults most likely to be exposed and infected.

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