The Impact of Schistosoma japonicum Infection and Treatment on Ultrasound-Detectable Morbidity: A Five-Year Cohort Study in Southwest China

Abstract

BackgroundUltrasonography allows for non-invasive examination of the liver and spleen and can further our understanding of schistosomiasis morbidity.Methodology/Principal FindingsWe followed 578 people in Southwest China for up to five years. Participants were tested for Schistosoma japonicum infection in stool and seven standard measures of the liver and spleen were obtained using ultrasound to evaluate the relationship between schistosomiasis infection and ultrasound-detectable pathology, and the impact of targeted treatment on morbidity. Parenchymal fibrosis, a network pattern of the liver unique to S. japonicum, was associated with infection at the time of ultrasound (OR 1.40, 95% CI: 1.03–1.90) and infection intensity (test for trend, p = 0.002), adjusting for age, sex and year, and more strongly associated with prior infection status and intensity (adjusted OR 1.84, 95% CI: 1.30–2.60; test for trend: p<0.001 respectively), despite prompt treatment of infections. While declines in parenchymal fibrosis over time were statistically significant, only 28% of individuals with severe parenchymal fibrosis (grades 2 or 3) at enrollment reversed to normal or grade 1 within five years. Other liver abnormalities were less consistently associated with S. japonicum infection.Conclusions/SignificanceParenchymal fibrosis is an appropriate measure of S. japonicum morbidity and can document reductions in disease following control efforts. Other ultrasound measures may have limited epidemiological value in regions with similar infection levels. Because severe fibrosis may not reverse quickly following treatment, efforts to reduce exposure to S. japonicum should be considered in combination with treatment to prevent schistosomiasis morbidity.

Use of Ultrasonography to Evaluate Schistosoma japonicum-Related Morbidity in Children, Sichuan Province, China, 2000–2007

“…Given good inter-observer agreement on 2007 readings of parenchymal grade, we feel that the longitudinal outcomes and associations made for this important measure are valid. Regarding our finding that hepatomegaly increased despite decreased infections, which is likely caused by recurrent infections, this finding was also observed in our analysis of the larger cohort that included adults 30 and has been documented by others. 25 However, the reliability of this measure along with all other hepatosplenic measures was poor to fair ( Table 4 ).…”

“…In an analysis of data from the larger cohort in this area (578 subjects, including adults), parenchymal fibrosis was significantly associated with infection status. 30 Our study may have been underpowered to detect the association between parenchymal fibrosis and infection status, because only 0.7-2.4% in our pediatric cohort had grade 2 disease (0.7-2.4% versus 18.5-21.8% in the larger cohort) and no subjects had grade 3 disease. Nonetheless, given that parenchymal fibrosis is rare in the pediatric population, left liver-lobe enlargement might be a more useful indicator of infection control in the Chinese pediatric community.…”

Decline in infection-related morbidities following drug-mediated reductions in the intensity of Schistosoma infection: A systematic review and meta-analysis

“…The relative intensity of infection is an important correlate of morbidity, because the formation of the disease is related to the daily deposition of parasite eggs into host tissues [17, 48–50]. While immediate granulomatous inflammation is the cause of some of the morbidities included in our review (hematuria, proteinuria, bladder irregularities for S .…”

Field Evaluation of a PCR Test for Schistosoma japonicum Egg Detection in Low-Prevalence Regions of China

“…28,29 However, low-intensity schistosomiasis infection when combined with low-intensity STH infection may synergistically increase the risk of anemia, 30 underscoring the importance of sensitive diagnostics in areas where multiple helminth species are present, as in the case in our study region. In addition, the ability to detect low-intensity infections will be a critical tool in the determination of a morbidity profile of such infections, allowing us to more fully characterize their clinical effects.…”