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istosomiases
Schistosomiases
Sch istosom iases are acute or ch ronic v isceral parasitic d iseases d ue to 5 species of
trem atod es (sch istosom es).
T h e th ree m ain species infecting h um ans are Schistosoma haematobium, Schistosoma
mansoni and Schistosoma japonicum. Schistosoma mekongi and Schistosoma intercalatum
h av e a m ore lim ited d istribution (see table next pag e).
H um ans are infected w h ile w ad ing / bath ing in fresh w ater infested w ith sch istosom e
larv ae. Sym ptom s occurring d uring th e ph ases of parasite inv asion (transient localized
itch ing as larv ae penetrate th e skin) and m ig ration ( allerg ic m anifestations and
g astrointestinal sym ptom s d uring m ig ration of sch istosom ules) are frequently
ov erlooked . I n g eneral, sch istosom iasis is suspected w h en sym ptom s of establish ed
infection becom e ev id ent (see table next pag e).
E ach species g iv es rise to a specific clinical form : g enito-urinary sch istosom iasis d ue to
S. haematobium, intestinal sch istosom iasis d ue S. mansoni, S. japonicum, S. mekongi and
S. intercalatum.
T h e sev erity of th e d isease d epend s on th e parasite load . H eav ily infected patients are
prone to v isceral lesions w ith potentially irrev ersible sequelae.
C h ild ren ag ed 5 to 1 5 years are particularly at risk: prev alence and parasite load are
h ig h est in th is ag e g roup.
A n antiparasitic treatm ent sh ould be ad m inistered to red uce th e risk of sev ere lesions,
ev en if th ere is a likelih ood of re-infection.
Geographic distribution of schistosomiasis in Africa (WHO)
150
Schistosomiases
Sch istosom iases are acute or ch ronic v isceral parasitic d iseases d ue to 5 species of
trem atod es (sch istosom es).
T h e th ree m ain species infecting h um ans are Schistosoma haematobium, Schistosoma
mansoni and Schistosoma japonicum. Schistosoma mekongi and Schistosoma intercalatum
h av e a m ore lim ited d istribution (see table next pag e).
H um ans are infected w h ile w ad ing / bath ing in fresh w ater infested w ith sch istosom e
larv ae. Sym ptom s occurring d uring th e ph ases of parasite inv asion (transient localized
itch ing as larv ae penetrate th e skin) and m ig ration ( allerg ic m anifestations and
g astrointestinal sym ptom s d uring m ig ration of sch istosom ules) are frequently
ov erlooked . I n g eneral, sch istosom iasis is suspected w h en sym ptom s of establish ed
infection becom e ev id ent (see table next pag e).
E ach species g iv es rise to a specific clinical form : g enito-urinary sch istosom iasis d ue to
S. haematobium, intestinal sch istosom iasis d ue S. mansoni, S. japonicum, S. mekongi and
S. intercalatum.
T h e sev erity of th e d isease d epend s on th e parasite load . H eav ily infected patients are
prone to v isceral lesions w ith potentially irrev ersible sequelae.
C h ild ren ag ed 5 to 1 5 years are particularly at risk: prev alence and parasite load are
h ig h est in th is ag e g roup.
A n antiparasitic treatm ent sh ould be ad m inistered to red uce th e risk of sev ere lesions,
ev en if th ere is a likelih ood of re-infection.
Geographic distribution of schistosomiasis in Africa (WHO)
150
