Clinical Diagnostic Parasitology Laboratory (CDPL)

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Intestinal parasites

Strongyloides

Faecal microscopy: UKAS accredited test

A concentration technique is routinely performed on all faecal samples for the presence of cysts, ova, and larvae.

Sample requirement:

Minimum of a quarter specimen pot of faecal sample. Ova, cysts, and parasites may be passed intermittently therefore three samples may be required to be examined. Ova, cysts, and parasites will diminish over time so it is ideal for the sample to be less than two days old upon receipt at LSTM. However, older stools will not be rejected.

Culture for Strongyloides/Hookworm: UKAS accredited test

Faeces are cultured for filariform larvae using the charcoal technique.

Sample requirements:

  • At least 50g (half pot) of faeces.
  • Ova, cysts, and parasites may be passed intermittently so three samples may need to be examined.

Key factors affecting tests:

Samples should NOT be stored in a refrigerator or cold room following collection as this may inhibit subsequent larval growth.

Microscopic image showing a Strongyloides stercoralis larva. The translucent, elongated parasitic worm has a curved body with visible internal structures, seen against a light background under high magnification.

Schistosomiasis

Faecal Parasite diagnosis – UKAS accredited test

Faecal microscopy 

A concentration technique is routinely performed on all faecal samples for the presence of cysts, ova, and larvae.

Sample requirements:

  • Minimum of a quarter specimen pot of faecal sample.
  • Ova, cysts, and parasites may be passed intermittently so three samples may need to be examined.
  • Ova, cysts, and parasites will diminish over time so it is ideal if the sample is less than two days old upon receipt at LSTM. However, older stools will not be rejected.

Urine techniques – UKAS accredited test

Schistosoma haematobium

Urine is tested by dipstick for the presence of blood/Hb, and RBCs. Urine is routinely filtered for Schistosomiasis ova using polycarbonate filters.

Sample requirements:

  • Ideally total 10.00-14.00 urine collection or terminal 12.00 sample

Key factors affecting test:

Random urine samples may give false-negative results.

Semen – UKAS accredited test

Seminal fluid microscopy is performed for schistosome ova.

Specimen requirements:

  • Age and volume of the sample is not critical.
Microscopic image showing a Schistosome egg with a distinct oval shape and a pointed spine. The translucent shell and internal granular contents are visible, surrounded by a green-tinted background of biological material.

Giardia

Faecal Parasite diagnosis – UKAS accredited test

Faecal microscopy

A concentration technique is routinely performed on all faecal samples for the presence of cysts, ova, and larvae. Direct saline smears are examined on samples that are 24 hours old or less where trophozoite stages of protozoan parasites are suspected.

Sample requirements:

  • Minimum of a quarter specimen pot of faecal sample.
  • Ova, cysts, and parasites may be passed intermittently so three samples may need to be examined.
  • Ova, cysts, and parasites will diminish over time so it is ideal if the sample is less than two days old upon receipt at LSTM. However, older stools will not be rejected.

Key factors affecting test: 

Trophozoites may only survive for up to 24 hours in voided faecal samples.

Giardia lamblia (intestinalis) Antigen

If cysts cannot be identified by routine microscopy faecal antigen detection is a sensitive method of diagnosis.

Sample requirements:

  • Specimens should be fresh (< 72 hours old).
  • OR, sample may be freshly-frozen at -20°C for up to 90 days if the test cannot be performed within 72 hours.
  • Minimum quarter pot of faecal specimen.
3D illustration of a Giardia lamblia parasite showing its teardrop-shaped body, two prominent nuclei, and multiple flagella extending outward. The transparent outer layer reveals internal structures typical of this intestinal protozoan.

Entamoeba histolytica

Faecal parasite diagnosis – UKAS accredited test

Faecal microscopy (including hot stool)

A concentration technique is routinely performed on all faecal samples for the presence of cysts, ova and larvae. Direct saline smears are examined on samples that are 24 hours old or less where trophozoite stages of protozoan parasites are suspected.

Sample requirements:

  • Minimum of a quarter specimen pot of faecal sample.
  • Ova, cysts, and parasites may be passed intermittently so three samples may need to be examined.
  • Ova, cysts, and parasites will diminish over time so it is ideal if the sample is less than two days old upon receipt at LSTM. However, older stools will not be rejected.

Key factors affecting test:

Trophozoites may only survive for up to 24 hours in voided faecal samples

If Entamoeba histolytica trophozoites are suspected a “hot” stool must be examined.

Hot stool sample requirements:

  • Specimen must reach the laboratory within 30 minutes of sample being produced and must be marked as a hot stool, so it can be examined with priority.
  • Methanol fixed faecal smears can be made at requesting site if the sample can not arrive at CDPL within 30 minutes. These smears can then be sent to CDPL for staining and examination.

Faecal Antigen detection

Entamoeba histolytica adhesin ELISA

To differentiate between cysts of E.histolytica/dispar as seen by faecal microscopy.

Sample requirements:

  • Samples must not be bloody.
  • The test must be performed on fresh (< 48 hour old) not fixed specimens
  • Unpreserved specimens should be kept at 2-8°C and tested within 48 hours of defaecation.
  • If the test cannot be performed within 48hours store sample at -20°C or lower until tested.
  • Do NOT send preserved specimens.
  • Minimum quarter pot of faecal specimen.

Key factors affecting test:

Test is not validated on samples older than specified.

Amoebiasis – examination of cyst aspirate/pus samples – UKAS accredited test          

Specimen requirements:

  • Requests for Entamoeba histolytica in samples of pus from liver abscesses should be examined within one hour of collection.
  • OR, fresh thin smears of pus should be made (minimum of three), fixed when dry (one minute in methanol) and sent for staining with pus sample.

Key factors affecting test:

About 30 minutes after aspiration of cyst pus/fluid, E.histolytica trophozoites become indistinguishable from macrophages.

Microscopic image showing clusters of Entamoeba histolytica trophozoites. The round, translucent protozoa with granular interiors are visible against a green-tinted background, representing the parasite responsible for amoebic dysentery.

Other intestinal protozoa

Faecal Parasite diagnosis – UKAS accredited test      

Faecal microscopy (including hot stool)

A concentration technique is routinely performed on all faecal samples for the presence of cysts, ova, and larvae. Direct saline smears are examined on samples that are 24 hours old or less where trophozoite stages of protozoan parasites are suspected.

Sample requirements:

  • Minimum of a quarter specimen pot of faecal sample.
  • Ova, cysts, and parasites may be passed intermittently so three samples may need to be examined.
  • Ova, cysts, and parasites will diminish over time so it is ideal if the sample is less than two days old upon receipt at LSTM. However, older stools will not be rejected.

Key factors affecting test:

Trophozoites may only survive for up to 24 hours in voided faecal samples.

If Entamoeba histolytica trophozoites are suspected a hot stool must be examined.

Hot stool sample requirements:

  • Specimen must reach the laboratory within 30 minutes of sample being produced and must be marked as a hot stool, so it can be examined with priority.
  • Methanol fixed faecal smears can be made at requesting site if the sample can not arrive at CDPL within 30 minutes. These smears can then be sent to CDPL for staining and examination.

Faecal staining methods

Cryptosporidia

Slides from concentrated faecal deposit are stained using the Z-N technique for identification of oocysts.

Sample requirements:

  • Minimum of quarter pot of faecal sample.
  • Ova, cysts and parasites may be passed intermittently so three samples may need to be examined.
Vintage scientific illustration plate showing detailed drawings of various intestinal protozoa species at different stages of development. The organisms are depicted with visible flagella, nuclei, and internal structures, highlighting morphological differences among protozoan parasites.

Intestinal cestodes – tapeworms

Faecal Parasite diagnosis – UKAS accredited test

Faecal microscopy

A concentration technique is routinely performed on all faecal samples for the presence of cysts, ova and larvae.

Sample requirements:

  • Minimum of a quarter specimen pot of faecal sample.
  • Ova, cysts, and parasites may be passed intermittently so three samples may need to be examined.
  • Ova, cysts, and parasites will diminish over time so it is ideal if the sample is less than two days old upon receipt at LSTM. However, older stools will not be rejected.

Whole worms/proglottids

Identification of whole worms/proglottids

Sample requirements:

  • Whole worms such as Ascaris may be stored in 10% formol saline. Suspected Taenia species proglottids are best stored in physiological saline and sent to the laboratory as soon as possible.
  • The use of 10% formol saline should be avoided unless the sample cannot be sent to the reference laboratory within three days.

Key factors affecting tests:

Identification may be difficult if formalin-fixed proglottids are sent for identification, however proglottids may disintegrate if in saline for three days or more.

Scientific illustration showing the anatomy and life stages of an intestinal cestode (tapeworm). The image includes the segmented adult worm (a), a detailed view of the scolex or head with suckers (b), a larval cyst form (c), and encysted larvae within muscle tissue (d).

Intestinal trematodes – flukes

Faecal Parasite diagnosis – UKAS accredited test

Faecal microscopy 

A concentration technique is routinely performed on all faecal samples for the presence of cysts, ova and larvae.

Sample requirements:

  • Minimum of a quarter specimen pot of faecal sample.
  • Ova, cysts, and parasites may be passed intermittently so three samples may need to be examined.
  • Ova, cysts, and parasites will diminish over time so it is ideal if the sample is less than two days old upon receipt at LSTM. However, older stools will not be rejected.

Sputum

Sputum microscopy is performed for parasitic ova.

Specimen requirements:

  • Age and volume of sample is not critical.
  • The laboratory does not process samples when a diagnosis of TB cannot be excluded.
Microscopic image of an intestinal trematode (fluke) stained pink to highlight internal structures. The flat, oval-shaped parasitic worm shows visible internal organs and reproductive structures, characteristic of flukes that infect the human intestine.