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Collection of Specimen
Procedure for microscopic examination (Figure 22.10)
(vaginal discharge)
T. vaginalis.
Candida.
J101
(b)
FIGURE 22.10
a a
a a
a
10s I
Medical Laborato Technology: Volume 2
vaginal or urethral exudates
zoites
0
FIGURE 22.11
Morphological chacte of common parasic protozoa
Laborato Diagnosis of Parasitic Infections
J109
TABLE 22.2
Stage of develo
hozoites
Tro
p
Ideng characte of E. histolica, E. coli and I. bOtschlii
ment
p
E. histolyca
E.coli
I. butschlii
Cysts
-
Cysts:
Medical Laboratory Technology: Volume 2
710
The T. hominis trophozoite has a nucleus with a small karyosome and unevenly distributed
chromatin in stained material. It has an irregular movement and does not move across the
eld. Trichomonas hominis does not have a known cyst stage. If the technician is unable to
dierentiate between the agellates - Giardia, Trichomonas or any other, just report ‘agellates
present’. Physical examination, clinical symptoms, condition of stool and the laboratory
report of ‘agellates present’ can help the physician to start therapy.
Cysts of G. lamblia are found in soft and formed stool and can be seen in concentrated stool.
Cysts do not have agella. They are oval-shaped, 8–12 μm in size, with a thick wall from
which the cytoplasm is often retracted and 2–4 nuclei located at one end of the cyst with a
small, central karyosome. The cytoplasm is clear and refractile when unstained and yellowish-green or bluish cytoplasm in iodine solution. An axoneme (precursor to agella) appears
as a folded ‘S’ shaped hair-like line placed lengthwise in the centre of the cyst.
Giardia lamblia trophozoites are tear-drop shaped, 12–15 μm in length, with a sucking disk
on the ventral surface, two anterior nuclei and eight agella. It is often described as having
the appearance of an owl, professor, or monkey.
The organism that imitates Giardia in many ways is Trichomonas hominis. It is harmless.
Identication is necessary so that it is not mistaken for G. lamblia. Trophozoites are slightly
smaller than those of G. lamblia; oval-shaped with two pointed poles. Motility is described as
irregular, with whirls and turns in all directions, seeming to vibrate. Four agella are present,
and an undulating membrane is extremely motile with rapid movement. There is a single nucleus that is dicult to see. The technician should be able to distinguish from G. lamblia based
upon shape (oval with pointed ends vs. tear drop), number of nuclei and undulating membrane.
Trichomonas Vaginalis
This is a pathogenic agellate causing disease in the genitourinary tract (Figure 22.11). It
is fairly common in women, especially during pregnancy or following vaginal surgery.
Symptoms of infection in women are persistent vaginal burning and itching associated with
a profuse white, frothy discharge. A wet mount of the freshly collected specimen, without
iodine stain, is the best way to diagnose T. vaginalis. Any moving protozoa you nd in the
discharge from the vagina are almost sure to be trophozoites of T. vaginalis. T. vaginalis does
not have a known cyst phase.
Leishmania
Leishmania is a blood parasite of humans and is the causal agent of leishmaniasis and
kala-azar, The infection is transmied through sand ies and leads and is common in tropical
countries. The disease causes cutaneous and mucocutaneous lesions or can spread to the
visceral organs.
Laboratory Diagnosis
Diagnosis is made by microscopic identication of the intracellular, non-agellated protozoa
on Giemsa-stained smear taken from cutaneous lesion or visceral biopsy. Host cells containing
a large number of these intracellular forms of the parasite are referred to as Leishman–
Donovan bodies
Donor blood must be tested for Leishmania infection in endemic areas by the formaldehyde
gel method.
Procedure
1. Take 1 mL serum in a small-size test tube (5 mL).
2. Add 1 drop of 40% formaldehyde (commercial grade).
3. Tilt the tube and watch for coagulation.
4. Complete coagulation occurs in few seconds in acute cases. The mixture of serum and
formaldehyde becomes turbid in 20 min.
Laborato Diagnosis of Parasitic Infections
Sporozoa
protozoa
lacks locomotor organs
anosomes
Sleeping sickness pnosomiasis)
tsetse y
Laboratory diagnosis of sleeping sickness (Trypnosoma)
Microscopy
Limitations
Serognosis
Card Agglutination Test
Detection of specic
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Medical Laborato Technology: Volume 2
antibody in blood
T. b.
ambiense
g
CATT
The micro-CATT
b. gambiense
b.
ambiense
g
Chagas Disease rypnosoma cr
Chagas disease American trypanosomiasis,
Laboratory Diagnosis
serological tests.
immuno-enzymatic assays
recombinant antigens
Ectoparasites en
doparasites
commensal,
T. va
inalis,
g
Laborato Diagnosis of Parasitic Infections
General group Morphological features
Protozoa (unicellular) Amoebae
Ciliates
Flagellates
Sporozoans
Helminths (multicellular) Trematodes
Cestodes
Nematodes
Organism
Entamoeba
Balantidium
Giardia
Crtosporidium, Isospora, Cyclospora
Fasciolopsis, Schistosoma
Taenia, Dipylidium, Hymenolepis
Enterobius, Ascaris
TABLE Classication of human parasites based on the fe cycle
Tphozoites: Cys:
Medical Laborato Technology: Volume 2
Platyhelminths:
matodes non-se
Fasciola, Fasciolopsis, Clonorchis, Paragonimus, Schistosoma
Schistosoma
Cestodes se
mented
g
mented
g
Laboratory invesation
Note
Laborato Diagnosis of Parasitic Infections
ELISA Update
FAST-ELISA
cross-react
Dot-ELISA
Luciferase Immunoprecipitation System (LIPS)
Rapid Antigen Detection System (ROTS)
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Medical Laborato Technology: Volume 2
TABLE 22.4
Taenia
Hymenol
µm)
,_
,-
µm), Clonorchis
µm),
Key to the identication of common helminth eggs*
ichuris
Ascaris
Enterobius
Strongyloides
Ancylostoma
Necator
Schistosoma monsoni
Schistosoma haematobium
Schistosoma japonicum
Fasciola
is
-
-
-
-
"Modied from Manual Of Basic Techniques r a Health Laborato. World Health Organization, Geneva, 1980.