|Home | About | Journals | Submit | Contact Us | Français|
With a rising immigrant population and increasing international tourism, schistosomiasis is a diagnosis to be borne in mind.
A woman from Zimbabwe, aged 23, attended for sexual health screening after an episode of haematuria that had resolved with trimethoprim. For the past three months she had also experienced irregular vaginal bleeding, lower abdominal pain and postcoital bleeding. On genital examination an ulcerated lesion, covered with purulent exudate, was seen on the posterior lip of the cervix. Swabbing uncovered punctuate erythematous areas. Tests for sexually transmitted infections including HIV were negative, but the cervical smear revealed Schistosoma haematobium eggs. A schistosomal antibody test and urine samples for schistosomal eggs were negative. She was treated with praziquantel 40 mg/kg body weight and at three months the cervical lesion had completely resolved. Repeat cervical smear at that time was negative for schistosomal eggs.
A man of 31 from Somalia attended after experiencing terminal haematuria for the past twelve months. On routine blood testing the only finding of note was slight eosinophilia. The red cell count in urine was >100 × 106/L but no schistosomal eggs were seen. Plain X-ray screening for sexually transmitted infections was negative and ultrasound of the urinary tract showed nothing abnormal. A schistosomal antibody test was positive at level four. He was treated with praziquantel 40 mg/kg and was free from haematuria one month and six months later.
Most cases of schistosomiasis in the UK are associated with travel to Africa, especially Malawi.1 The infective agent is a water-borne larva (the cercaria) that penetrates intact human skin in contaminated water. The adult trematode worms reside in mesenteric veins (S. mansoni and S. japonicum) or in perivesical veins (S. haematobium) and produce eggs. Chronic disease results from the host's immune response to the eggs. S. japonicum is confined to Asia.
Early symptoms of S. haematobium infection are haematuria and dysuria, with genital disease in one-third of affected women.2 Vulval and perianal lesions may be hypertrophic, ulcerative, fistulous or wart-like and can facilitate transmission of HIV. Cervical lesions may be cauliflower-like growths, ulcerative or polypoidal. Later features are bladder calcification and cancer, ureteric obstruction and renal failure.
Diagnosis depends on detection of eggs in tissue, urine or faeces. Urine samples should be collected between 12 and 2 pm after the patient has taken light exercise. The shedding of eggs is not constant so repeat samples may be necessary. Cervical disease can be detected by smear or biopsy.3,4 Serological diagnosis is by enzyme-linked immunosorbent assay, which is 76% sensitive for S. haematobium4 but does not become positive for 6–12 weeks after initial infection. A new technique seeks DNA sequences from the parasite. The mainstay of treatment is praziquantel: a single dose of 40 mg/kg gives a cure rate of 60–90%, assessed by examination of faeces or urine one month after treatment.