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6. Parasitic diseases
Intestinal protozoan infections
(parasitic diarrhoea)
T h e m ost im portant intestinal protozoan infections are am oebiasis ( Entamoeba
histolytica) , g iard iasis ( Giardia lamblia) , cryptosporid iosis ( Cryptosporidium sp) ,
cyclosporiasis (Cyclospora cayetanensis) and isosporiasis (Isospora belli).
Intestinal protozoa are transm itted by th e faecal-oral route (soiled h and s, ing estion of
food or w ater contam inated w ith faeces) and m ay cause both ind iv id ual cases of
d iarrh oea and epid em ic d iarrh oea outbreaks.
Clinical features
– A m oebiasis g iv es rise to blood y d iarrh oea, see C h apter 3 , pag e 8 8 .
– C linical presentation of g iard iasis, cryptosporid iosis, cyclosporiasis and isosporiasis
is v ery sim ilar:
• D iarrh oea is usually m ild and self-lim iting , except in ch ild ren and patients w ith 6
ad v anced H I V d isease (C D 4 < 2 0 0 ) . T h ese patients are likely to d ev elop
sev ere,
interm ittent or ch ronic d iarrh oea th at m ay be com plicated by m alabsorption w ith
sig nificant w asting (or failure to g ain w eig h t in ch ild ren) or sev ere d eh yd ration.
• Stools are usually w atery, but steatorrh oea (pale, bulky, fatty stools) m ay be found
in th e ev ent of second ary fat m alabsorption; stools m ay contain m ucus.
• D iarrh oea is usually associated w ith non- specific g astrointestinal sym ptom s
(abd om inal d istension and cram ps, flatulence, nausea, anorexia), but patients h av e
low -g rad e fev er or no fev er.
Laboratory
D efinitiv e d iag nosis rel ies on parasite id entification in stool specim ens
( troph ozoites and cysts for g iard ia; oocysts for cryptosporid ium , cyclospora,
isospora) . T w o to th ree sam ples, collected 2 to 3 d ays apart are necessary, as
path og ens are sh ed interm ittently.
Treatment
– C orrect d eh yd ration if present (for clinical features and m anag em ent, see pag es 3 1 5
and 3 2 1 ).
147
Intestinal protozoan infections
(parasitic diarrhoea)
T h e m ost im portant intestinal protozoan infections are am oebiasis ( Entamoeba
histolytica) , g iard iasis ( Giardia lamblia) , cryptosporid iosis ( Cryptosporidium sp) ,
cyclosporiasis (Cyclospora cayetanensis) and isosporiasis (Isospora belli).
Intestinal protozoa are transm itted by th e faecal-oral route (soiled h and s, ing estion of
food or w ater contam inated w ith faeces) and m ay cause both ind iv id ual cases of
d iarrh oea and epid em ic d iarrh oea outbreaks.
Clinical features
– A m oebiasis g iv es rise to blood y d iarrh oea, see C h apter 3 , pag e 8 8 .
– C linical presentation of g iard iasis, cryptosporid iosis, cyclosporiasis and isosporiasis
is v ery sim ilar:
• D iarrh oea is usually m ild and self-lim iting , except in ch ild ren and patients w ith 6
ad v anced H I V d isease (C D 4 < 2 0 0 ) . T h ese patients are likely to d ev elop
sev ere,
interm ittent or ch ronic d iarrh oea th at m ay be com plicated by m alabsorption w ith
sig nificant w asting (or failure to g ain w eig h t in ch ild ren) or sev ere d eh yd ration.
• Stools are usually w atery, but steatorrh oea (pale, bulky, fatty stools) m ay be found
in th e ev ent of second ary fat m alabsorption; stools m ay contain m ucus.
• D iarrh oea is usually associated w ith non- specific g astrointestinal sym ptom s
(abd om inal d istension and cram ps, flatulence, nausea, anorexia), but patients h av e
low -g rad e fev er or no fev er.
Laboratory
D efinitiv e d iag nosis rel ies on parasite id entification in stool specim ens
( troph ozoites and cysts for g iard ia; oocysts for cryptosporid ium , cyclospora,
isospora) . T w o to th ree sam ples, collected 2 to 3 d ays apart are necessary, as
path og ens are sh ed interm ittently.
Treatment
– C orrect d eh yd ration if present (for clinical features and m anag em ent, see pag es 3 1 5
and 3 2 1 ).
147
