Nejm 2002;346:1212; Am J Pub Hlth 2004;94:738 (swimmers' itch)

Cause:Schistosoma mansoni, japonicum, and haematobium; swimmers' itch from S. dermatidis(Maine Epigram 8/87)

Pathophys:

Focal granulomas, fibrosis, vasculitis

Swimmer's itch due to allergic reaction to worms on 2nd exposure

Free-swimming cercaria penetrate skin or ingested, become schistosomula in blood and mature into adults in blood vessels. They then deposit in body tissues selectively (S. mansoniand S. japonicumabout gi tract, S. haematobiumabout bladder); there they mate and lay eggs that work out to feces or urine, are excreted into water where become miracidium, which invades a snail, and reproduce again, and eventually are released as cercaria. Can live 30-40 yr in man

In S. dermatidisswimmer's itch, only cercarial penetration of skin by nonhuman schistosomes occurs; cycle stopped there

S. mansoniin Caribbean, Africa, Middle East; S. haematobiumin Africa, Far and Middle East; S. japonicumin Far East (Nejm 1983;309:1533). S. dermatidisin marine or freshwater

Sx:

Chills, diarrhea, abdominal pain, weight loss, bloody urine/stool

S. dermatidis:swimmer's itch

Si:

Hepatosplenomegaly (70%), fever (60%), diarrhea (60%)

S. dermatidis:skin welts or swelling

Granulomatous response to eggs anywhere including brain, skin, liver with cirrhosis and varices, gu tract with obstruction and secondary infections and immune complex nephritis (Ann IM 1975;83:148)

in swimmer's itch: r/o sea bather's eruptions from anemone medusae (Nejm 1993;329:542)

Lab:

Bact: Stool/urine show typical eggs: S. japonicum,round; S. ahematobium,single-tailed; S. mansoni,forked-tailed

Hem:Eosinophils increased

Path:Biopsy of rectum, liver, bladder may show eggs

Serol:Immunofluorescent antibody titers; skin test pos after 20 wk (10/10)

Rx:

Preventive: aggressive sewage/sanitation controls work effectively (Nejm 2009;360:121)

Praziquantel 20 mg/kg bid × 1 d; good vs all types; 70% cure (Nejm 1984;310:298)

Swimmer's itch, no rx