Evolution of schistosomiasis-induced pathology after therapy and interruption of exposure to schistosomes: a review of ultrasonographic studies

Acta Trop. 2000 Oct 23;77(1):111-31. doi: 10.1016/s0001-706x(00)00125-x.

Abstract

Ultrasonography (US) is suitable for diagnosing schistosomiasis-related organic pathology and is particularly useful to assess its evolution after therapy and/or interruption of exposure to the Schistosoma parasites. Evolution of pathology after treatment: Regression of hepatic abnormalities in Schistosma mansoni-infected children and adolescents has been observed already from 7 months post-therapy on. This does, however, not occur in all cases: individual differences are great ranging from spontaneous regression of pathology without treatment to persistence of pathology lasting for years after therapy even without re-infection. Intensity and duration of exposure, different parasite strains, patients' age and genetic background all influence the evolution of pathology. In communities at continuous exposure to S. mansoni infection, repeated re-treatment is required to control hepatosplenic morbidity. In Schistosoma japonicum infection, changes around the portal tree may regress, but characteristic diffuse abnormalities described as 'network pattern' abnormalities do not resolve. In Schistosoma haematobium infection bladder abnormalities and urinary tract obstruction frequently resolve after treatment. Clinically relevant pathology may resurge from 1 year after therapy on if exposure continues. Subjects with more advanced pathology before therapy, appear to be at higher risk of pathology re-appearance. Evolution of pathology after interruption of exposure to schistosomiasis: Knowledge on the evolution of pathology induced by S. mansoni is limited to some reports in emigrants and to the experience of ultrasonographists working in areas, where transmission has been partially interrupted. Due to the longevity of the parasite, infection may last for many years. Even after elimination of the parasites severe pathology may persist for long. In S. haematobium infection spontaneous healing after interruption of re-exposure may occur, but cases have been reported where urogenital lesions led to complications many years after exposure. Contrary to hepatosplenic and urinary pathology, knowlegde on the evolution of other organic abnormalities is very limited: studies on the evolution of biliary abnormalities or intestinal pathology have not been published. Genital pathology may be induced by all Schistosoma spp. Post-therapy evolution of genital schistosomiasis is largely ignored. In some European travellers partial regression of prostatic fibrosis has been described. Schistosomal adnexitis leading to infertility and/or ectopic pregnancy has been reported occurring many years after interruption of exposure. Ultrasonography (US) has never been used to study the influence of schistosomiasis on pregnancy. Concluding, current knowlegde on the evolution of pathology after treatment and/or interruption of exposure is still fragmentary. Frequently, fibrosis reverses after therapy, but advanced pathology may persist for long. Therefore, the possibility of severe clinical complications has to be taken into account, even if the infection is inactive since many years. In interventions aimed at controlling schistosomiasis-related morbidity, evolution of pathology must be monitored by US in representative patient cohorts. Further systematic US-studies are needed not only on the evolution of hepatosplenic and urinary pathology but also on that of intestinal, biliary and genital pathology induced by schistosomiasis, as well as on the influence of schistosomiasis on the outcome of pregnancy.

Publication types

  • Review

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Animals
  • Anthelmintics / therapeutic use*
  • Child
  • Female
  • Follow-Up Studies
  • Gallbladder / pathology
  • Humans
  • Hypertension, Portal / diagnostic imaging
  • Hypertension, Pulmonary / diagnostic imaging
  • Intestines / pathology
  • Liver / pathology
  • Liver Neoplasms / diagnostic imaging
  • Male
  • Middle Aged
  • Praziquantel / therapeutic use
  • Pregnancy
  • Pregnancy Complications, Parasitic / diagnostic imaging
  • Schistosomiasis / diagnostic imaging
  • Schistosomiasis / drug therapy
  • Schistosomiasis / pathology*
  • Schistosomiasis haematobia / diagnostic imaging
  • Schistosomiasis haematobia / pathology
  • Schistosomiasis japonica / diagnostic imaging
  • Schistosomiasis japonica / pathology
  • Schistosomiasis mansoni / diagnostic imaging
  • Schistosomiasis mansoni / pathology
  • Time Factors
  • Treatment Outcome
  • Ultrasonography / economics
  • Ultrasonography / trends*

Substances

  • Anthelmintics
  • Praziquantel