Laboratory Diagnosis of Parasitic Infections PDF Fall 2024

9/6/2024 L A B O R AT O RY D I A G N O S I S OF PA R A S I T I C I N F E C T I O N S D IAGN OS IS OF IN FECTED C A S E Failure to demonstrate or recover a parasite does not exclude the possibility of infection. Many parasites, especially the protozoa, can be identified only...

9/6/2024 L A B O R AT O RY D I A G N O S I S OF PA R A S I T I C I N F E C T I O N S D IAGN OS IS OF IN FECTED C A S E Failure to demonstrate or recover a parasite does not exclude the possibility of infection. Many parasites, especially the protozoa, can be identified only by microscopic examination. This requires considerable skill and apart from being time-consuming and labor- intensive the method has limitations. 1  9/6/2024 History (Age, occupation, residency, previous infection) Presumptive Complaint diagnosis Clinical examination CASE Investigations: DIAGNOSIS -Laboratory investigations -Radiology Confirm the -Surgical intervention (Exploratory) diagnosis 2  9/6/2024 S TO O L S A M P L E C O L L E C T I O N : Sample is collected in a clean, dry screw-top container. Complete label with patient name, date of birth and the date. Do not contaminate specimen with urine, residual soap or disinfectants, which will destroy amoebae. Specimens in diapers are not acceptable. Handled carefully, wash hand thoroughly. Samples should be fresh (esp. amoeba, ciliates) or preserve the specimen as soon as possible. Liquid and soft stool examined within 15 min Stop taking the following products 3 days before analysis: Antacids, Antibiotics, Antiparasitic drugs, Barium, Enema product, Kaolin products, Oily laxatives 3  9/6/2024 Abnormal Color Consistency features Adult parasite Formed (F) Adult helmith or Brown/Bright red Soft (S) segments e.g. or dark red/Pale Mucus (M)/ Blood Ascaris worm, E. yellow/ Loose (L) (B) vermicularis, Taenia white/green Watery (W) spp. M A C R O S C O P I C E X A M I N AT I O N 4  9/6/2024 M I C RO S C O P I C E X A M I N AT I O N Direct smear method It is a fast, simple procedure and provides a quick answer when possible. It can be used as a screening test to check trophozoite motility. It can be prepared directly from fecal material or from concentrated specimen. Negative: Results should be confirmed by: Concentration Methods Or Permanent Stain Methods 5  9/6/2024 Cover without air bubble and examine immediately Wet mount Detect motile trophozoites and larvae, ova (eggs) and cysts Stain glycogen and the nuclei of cysts, differentiating cysts from white blood cells S T O O L E X A M I N AT I O N Staining saline preparation with methylene blue With Pasteur pipette, allow a drop of methylene blue solution to run under the coverslip over the saline preparation (stain the nuclei of any cell present and distinguish the lobed nuclei of polymorphs from the large single nuclei of mucosal cells). If a drop of eosin solution is added, the whole field becomes stained except for the protozoa (particularly amoebae), which remain colorless and are thus easily recognized. 6 9/6/2024 7  9/6/2024 S E D I M E N TAT I O N M E T H O D All types of eggs and cysts can be recovered by sedimentation. Parasites settle down more rapid by centrifugation. Larger food particles can be removed by filtration through a sieve with a pore size enough to retain these particles. Adding formalin for fixation, and ethyl acetate to remove organic materials especially fat increases the efficiency of detection. Formalin-Ethyl Saline Acetate sedimentation Sedimentation 1g 8  9/6/2024 F L O TAT I O N M E T H O D Parasites are recovered in the surface film, and debris remains in the bottom of the tube. Cleaner preparation than does the sedimentation procedure. Disadvantage: Opercualted eggs and/or very dense eggs do not concentrate well. Protozoan cysts become distorted and difficult to identify. Simple salt flotation Zinc sulphate centrifugal flotation Sheather`s sugar flotation 9  9/6/2024 S TO O L E X A M I N AT I O N P E R M A N E N T S TA I N E D S M E A R S Helpful in identifying Protozoa (esp. Flagellates) not helminth (helminth and larva retain too much stain and are distorted). Used whenever parasite cannot be detected in either direct wet prep. or concentration deposit Stay for long time 10  9/6/2024 S T O O L E X A M I N AT I O N K AT O T E C H N I Q U E The Kato-Katz technique is a widespread tool in intestinal helminth epidemiological surveys, for diagnosing and quantifying soil- transmitted helminth (STH) and Schistosoma mansoni infections – (eggs per gram of feces ) Egg count/ g stool Egg quant. Of: Ascaris, Whip worm, Hookworms, S. mansoni S T O O L E X A M I N AT I O N S TO L L’ S T E C H N I Q U E Egg count/ g stool Egg quant. Of: Ascaris, Whip worm, Hookworms, S. mansoni 11  9/6/2024 S TO O L E X A M I N AT I O N BAERMANN TECHNIQUE Based on the active migration or movement of larvae. Feces are suspended in water. The larvae move into the water. They sink to the bottom and can be collected for identification. Detection Of Nematode L. /stool, soil C U LT U R E O F N E M AT O D E L A R V A Time consuming- Cultures for Nematode larvae using Filter paper culture for inaccurate Larvae of: St. stercoralis (A,L) and Hookworms 12  9/6/2024 I N D I R E C T I M M U N O LO G I C A L METHODS Antigen detection Antibody detection Specific/accurate/active infection/early/ Ab remain in serum for months even after cure quantitative 13  9/6/2024 Hemagglutination Inhibition Test Latex agglutination Test 14  9/6/2024 ELISA 15 9/6/2024 16  9/6/2024 M O L E C U L A R B I O LO G I C A L TECHNIQUE DNA probe and PCR-based assays to identify and detect parasites are technically complex; however, they have high sensitivity, directly detect parasites independent of the immunocompetence or previous clinical history of the patient, and can distinguish between organisms that are morphologically similar. DNA probes are stretches of single-stranded DNA used to detect the presence of complementary nucleic acid DNA preparations extracted from sequences (target sequences) by hybridization. fecal samples are tested by PCR with diagnostic primers. Amplified DNA DNA probes are usually labelled, for example with fragments are electrophoretically radioisotopes, epitopes, biotin or fluorophores to enable resolved on an agarose gel for analysis their detection. of results. 17