Intestinal Protozoa

For the major parasitic causes of human gastroenteritis, please see individual sections on:

• Amoebiasis
• Cryptosporidiasis
• Cyclosporiasis
• Giardiasis
• Microsporidia.

In addition, non-pathogenic protozoa such as: Entamoeba coli, Entamoeba hartmani, Entamoeba dispar (indistinguishable from Entamoeba histolytica as cysts by morphology), Iodamoeba buetschlii, Endolimax nana, Chilomastix mesnili and Blastocystis hominis will also be reported if viewed by microscopy.

Diagnosis of intestinal protozoa by microscopy

• Sample type: Stool samples for the demonstration of trophozoites, cysts and oocysts should be forwarded with the minimum of delay (other sample types may also be analysed).

For further information on the diagnosis of intestinal protozoa by microscopy please refer to the relevant section(s) of this manual.

Diagnosis of intestinal protozoa by PCR

• Sample type: Stool samples for the demonstration of trophozoites, cysts and oocysts should be forwarded without fixatives (other sample types may also be analysed).

PCR is currently available only for Giardiasis, Cryptosporidiasis, Amoebiasis and Cyclosporiasis. For further information on the diagnosis of these protozoa by PCR please refer to the relevant section(s) of this manual.

Diagnosis of intestinal protozoa by serology

For Entamoeba histolytica infection, serology gives very good results in cases of amoeboma. In amoebic colitis the test is positive, often at low titre, in about 75% of cases.

In cyst passers it is often negative and in other cases it may be positive because of past infection. The test is therefore not suitable for the investigation of vague abdominal symptoms or as a routine check. For further information on the diagnosis of amoebiasis please refer to the relevant section of this manual.

For Giardiasis and other intestinal protozoal pathogens, we are unable to offer serological investigation. Please send a stool sample for PCR and Microscopy – please refer to the relevant section(s) of this manual.