9.
General principles of Laboratory
diagnosis of parasitic diseases
Competency
MI 1.2: Perform and identify the different causative agents of infectious diseases by Gram
Stain, ZN stain and stool routine microscopy
Specific Learning Objectives:At the end the session, the students shall be able to,
Describe general steps in the laboratory diagnosis of parasitic infections
Discuss the types of clinical specimen used in the laboratory diagnosis of parasitic
infections
Diagnose the underlying parasitic infection based on the history and clinical
symptoms and suggest the suitable laboratory test in the given case.
Perform saline and iodine mount from the given stool sample and identify various
morphological forms of parasites.
Identify various parasitic forms in the peripheral smear.
Describe the role of immunological tests in the diagnosis of parasitic diseases.
Exercise 9:
1) Describe general steps in the laboratory diagnosis of parasitic infections
1.Macroscopic Examination for stool consistency, color and mucoid and bloody.
2.Microscopic Examination : Saline mount for Tropozoits.
: Iodine Mount for Cyst and Ova.
3.Concentration Techniques :Sedimentation techniques for eggs and cyst.
:Floatation techniques for helminthic eggs and protozoan cysts.
2) Describe the collection of stool specimen for parasitic examination
1.Stool specimen should be collected in a wide-mouthed clean,leak-proof and screw capped containers.
2.Timing of collection should be before antiparasitic drugs and closer to the onset of symptoms.
3.Three stool specimen collected on alternate days(within 10 days) but in case of intestinal amoebiasis 6
specimens are collected.
4.Fecal specimens should be kept at room temperature with preservatives (10%formalin) added to it.
5.Perianal swabs is used for detection of enterobius vermicularis, schistosoma mansoni and taenia species.
6.By Endoscopy or by Entero-test duodenal fluid is collected for Giardia intestinalis and larva of
strongloides stercoralis.
2) Enumerate different types of clinical specimen (other than stool) used for diagnosis of
parasitic infections and indicate the clinical conditions.
Specimen Clinical condition/s
blood Fever and chills, headache, myalgias, arthralgias, splenomegaly, anemia,
thrombocytopenia, hypoglycemia, pulmonary or renal dysfunction, and neurologic
changes.
Stool Amoebic dysentery, GI symptoms, malnutrition, growth retardation, Iron deficiency
anemia and intestinal obstruction.
Vaginal swab In women - with a purulent discharge, vulvar and cervical lesions, abdominal pain,
dysuria and dyspareunia.
In men - urethritis, epididymitis, and prostatitis
Fluid Headache, fever, nausea, and vomiting with Later symptoms of neck stiffness,
aspirate(CSF) lethargy, confusion/disorientation, photophobia, seizures, decreased vision, redness,
foreign body sensation, photophobia, tearing, and discharge
3) Draw the colored labeled diagrams of common parasitic form seen in stool
4) Draw the colored labeled diagrams of common parasitic form seen in peripheral blood
smear
5) Enumerate immunological tests used in the diagnosis of parasitic infections and their
applications.
Immunological tests Applications
Enzyme-linked immunosorbent assay and Toxoplasmosis, Toxocariasis, Leinshmaniasis, Chagas’ disease,
radio immunoassay Malaria and Schistosomaisis.
Indirect haemagglutination test Amoebiasis, Hydatid disease, Filariasis, Cysticercosis and
Strongylodiasis
Indirect fluorescent antibody test Amoebiasis, Malaria, Toxoplasmosis and Schinstosomiasis
Complement fixation test Paragonimiasis, Chagas’ disease and Leishmaniasis
Agglutination tests
Direct agglutination Visceral leishmaniasis
Bentonite Floculation Trichinellosis and hydatid disease
Assessment
Sl.No. Student’s performance Score#
1 Comes prepared with requisite prior knowledge 1 2 3
2 Participates actively and contributes to discussion during SGT 1 2 3
3 Shows professional conduct during the Teaching Learning 1 2 3
session
4 Completes the record book activities in time 1 2 3
5 Shows evidence of learning the new skills 1 2 3
(Intellectual/Psychomotor)
Total score /15
(Can be reduced to 5 for convenience)
Faculty Remarks/Feedback:
Date : Faculty Name & Signature
# Mark as 1, 2, 3 for ‘Not satisfactory’, ‘satisfactory’ & ‘Very Good’ respectively
Certifiable Skill Exercise
Exercise 9.2: Stool Examination
A lady aged 22 years complains of abdominal discomfort and altered bowel habits
since one week. She has submitted stool sample. Perform stool examination to look for
parasitic elements. Record your observations and interpret the results.
Entamoeba histolytica
Observations Protozoan trophozoites and cysts.
Inference Entamoeba histolytica
Skill Certification
Competency No.: MI 1.2 Competency: Stool Examination (1)
Student’s Performance Max. Marks Marks
(05) Scored
Performs skill by following all the steps correctly 02
Focusses the preparation appropriately 01
Identifies the structures correctly and interprets. 01 (0.5+0.5)
Draws colored labelled diagram of the microscopic field and 01 (0.5+0.5)
writes the report
Score
Rating Rubric Rating
Below expectations (B) (Score – 1, 2, 2.5)
Meets expectations (M) (Score – 3, 3.5)*
Exceeds expectation (E) (Score – 4, 4.5, 5)
CERTIFICATION NO YES
(*Students should secure ‘M’ or ‘E’ to be able to get
Certification in a given skill)
Date Faculty Name & Signature
