Decreased Sensitivity of Schistosoma sp. Egg Microscopy in Women and HIV-Infected Individuals

It has been postulated that impaired host immunity due to HIV infection reduces parasite egg excretion. Schistosoma/HIV interactions have also been shown to differ by sex. We hypothesized that egg excretion would vary based on both HIV status and sex. We examined data from more than 1,700 participants in eight studies conducted in northwest Tanzania between 2010 and 2016. Schistosoma infection was defined by circulating anodic antigen (CAA) serum levels ≥ 30 pg/mL and/or egg positivity in either stool by Kato Katz method or urine by filtration. We used multivariable analyses to determine the impact of confounding factors such as sex, age, previous praziquantel treatment, and worm burden as measured by serum CAA level, on the relationship between egg excretion and HIV status. HIV-infected individuals were significantly less likely to excrete schistosome eggs than HIV-uninfected individuals, even after controlling for worm burden and sex (OR = 0.6 [0.4, 0.9], P = 0.005). Furthermore, after controlling for worm burden and HIV status, women had lower odds of egg excretion than men (OR = 0.4 [0.3, 0.5], P textless 0.001). Sensitivity of egg microscopy was lower in HIV-infected women than HIV-uninfected men (411 P textless 0.001), whereas sensitivity in women remained low in both groups (337 P = 0.664). Our study is the first to report that women with Schistosoma infection excrete fewer eggs than men for a given worm burden, regardless of HIV the status. These findings suggest that guidelines for use of microscopy to diagnose Schistosoma infections in HIV-infected individuals and in women merit reconsideration.