Medical Parasitology PDF

 is the study of parasites, their hosts, and the relationship between them. ✓ parasite: is an organism that live on or within another organism called the host. ✓One of the largest fields in parasitology, ✓It deals with the parasites that infect MAN, the diseases c...

 is the study of parasites, their hosts, and the relationship between them. ✓ parasite: is an organism that live on or within another organism called the host. ✓One of the largest fields in parasitology, ✓It deals with the parasites that infect MAN, the diseases caused by them, clinical picture various methods of their diagnosis treatment finally their prevention & control. IMPORTANT TERMS: Worm Protozoa Egg Cyst Larva Trophozoite Samples Others IV- Blood III- Sputum II- Urine I- Immuno I- Stool Diagnostics Macroscopic Examination Microscopic Examination Macroscopic Examination The fecal specimen should be examined for ✓consistency ✓presence of blood ✓Mucus ✓ worms ✓ proglottids. Microscopic Examination Wet Preparation Concentration Methods Kato Tech Microscopic Examination Direct Wet Method Stained Wet Method A small portion of stool is mixed A drop of Lugol’s iodine is with 0.85% saline drop on a slide mixed with a small portion of using an applicator. stool on a slide and cover- slipped. This preparation can detect eggs This wet preparation detects and larvae of helminthes and protozoan cysts. motile protozoan trophozoites. A concentration procedure is performed mainly to ✓separate the parasites from fecal debris ✓ making them more visible ✓It also increases the numbers of ova (worms) or cysts (protozoa) in the sediment. The two most commonly used methods SEDIMENTATION METHOD FLOATATION METHOD In both methods, the first step is centrifugation at 2500 rpm/min.  Sedimentation Method Floatation Method The sediment is resuspended in The sediment is resuspended in formalin and then ethyl acetate is zinc sulphate. added. It detects helminth eggs and The top fluid is examined larvae and protozoal cysts which for eggs and larvae and cysts are found in the “sediment”. “floated”. After concentration, the material is stained with iodine and examined microscopically.  Stool is mixed with glycerin to allow clearing (makes transparent) of fecal debris making eggs visible. Can be used for counting eggs/gram feces. I- Stool Examination II- Urine Examination III- Sputum Examination IV- Examination of Other Specimens V- Blood Examination VI- ImmunoDiagnostics  Examination of urine specimens may be useful in diagnosing infections caused by Schistosoma haematobium. Detection of eggs in urine can be accomplished using direct detection or concentration using the sedimentation centrifugation technique. Eggs may be trapped in mucus or pus and are more frequently present in the last few drops of the specimen rather than the first portion.  Occasionally, intestinal parasites may be detected in sputum. The specimen should be a deep sputum rather than primarily saliva, and it should be delivered immediately to the laboratory. Microscopic examination should include saline wet- mount and permanent stain preparations.  Next to faeces, the largest number of parasites are found in blood Two types of blood films are prepared for the diagnosis of blood parasite infections: thin films and thick films. Thin Film Thick Film The blood is spread over The red cells are lysed the slide in a thin (single- before staining, and only cell) layer. the white blood cells, platelets, and parasites (if present) are visible. The red blood cells The red blood cells are remain intact after lysed. staining For Heavy infection light infections Staining of blood film ✓Giemsa stain is the preferred stain  Immunodiagnostic methods have long been used as aids in the diagnosis of tissue parasitic diseases. The majority of these serologic tests are based on the detection of specific antibody responses or specific parasite antigen to the presence of the parasite. The analytical approaches include the use of: Classical agglutination Complement fixation Gel-diffusion methods Immunofluorescence Enzyme immunoassay (EIA) Western blot assays. THE PARASITOLOGY COURSE INCLUDES THE FOLLOWING SUBJECTS: i. Helminths: multicellular parasites. ii. Protozoa: unicellular parasites. SOME BASIC TERMS:  Lifecycle  Host (Definitive/ intermediate)  Habitat  Diagnostic stage  Infective stage  Mode of infection (Mode + Inf. stage)  Lab diagnosis (Tech + Diag. stage) TYPES OF HOSTS:  Definitive host: is that host harboring the adult or sexually mature stage of the parasite.  Intermediate host: is that host in which the immature or larval stage of the parasite is found or in which the parasite multiplies asexually.  Reservoir host: is an animal harboring the parasite to ensure continuity of its life cycle and act as additional source and a store of infection.  Vector: is usually an arthropod host in which biological changes or multiplication of a parasite take place to carry that parasite to its specific host. DON’T BE CONFUSED Unfertilized egg: it will eventually die if no fertilization occurs. Fertilized Egg: most probably will continue to become mature embryonated egg. Embryonated Egg: once it becomes embryonated, it is infective. Larvated Egg: it is ready to release the larvae and it is infective.  CLASSIFICATION OF HELMINTHES Ex. Class Taenia saginata/solium Cestoda Echinococcus granulosus (Tape worms) Hymenolepis nana Phylum Platyhelminthes (Flat worms) Fasciola hepatica/ gigantica Fasciolopsis buski Trematoda Worms Clonorchis sinensis (flukes) Heterophyes heterophyes Schistosoma mansoni/ hematobium Ascaris lumbricoides Trichuris trichiura Enterobius vermicularis Nemathelminthes Anchylostoma duodenale (Round worms) Nematoda Trichinella spiralis Loa loa Wuchereria bancrofti Onchocerca volvulus Dracunculus medinensis NEMATODES – PART 1 ✓Nematodes or round worms (from Greek : nema, nematos = thread and ode = like) ✓These worms are characterized by the following general features : cylindrical, round or oval. Non segmented, have well developed digestive tract. Sexes are separate the male is shorter and more slender than female. Nematodes infecting man may be divided into intestinal and tissue nematodes  have no intermediate host. These include : a) Small intestine: 1. Ascaris lumbricoides. 2. Ancylstoma duodenale. 3. Trichinella spiralis. b) Large intestine: 1. Trichuris trichiura. 2. Enterobius vermicularis.  Larvae mature in lungs 10-14 days Male 15 cm Female 30 cm 18 days – several weeks to become embryonated eggs.  Parasite Disease Hosts Habitat Ascaris Ascariasis DH: Man Small intestine lumbricoides (Giant intestinal round worm) I.S Mode of infection D.S Lab diagnosis Embryonated eggs Ingestion of food and Fertilized and Stool examination water contaminated unfertilized eggs. showing fertilized and unfertilized with embryonated (unembryonated eggs (un- eggs. eggs) embryonated eggs). Occasionally, sputum examination showing larvae. 15 – 30 days to become infective  Parasite Disease Hosts Habitat Trichuris Trichuriasis DH: Man Large intestine trichiura (Whip Worm) I.S Mode of infection D.S Lab diagnosis Embryonated eggs Ingestion of food and Fertilized and Stool examination water contaminated unfertilized eggs. showing fertilized and unfertilized with embryonated (unembryonated eggs (un- eggs. eggs) embryonated eggs).  The female Enterobius vermicularis exits through the anus and deposits her eggs on the perianal area. Best sampling occurs in the morning just after waking before bathing or a bowel movement. The sticky paddle/ scotch tape/ NIH swab is then placed into the container supplied or if tape is used it is attached to a glass slide or placed in a suitable specimen container and transported to the laboratory. Sticky Paddle NIH Swab  By gently applying the sticky surface to the perianal area pinworm eggs or at times intact adult pinworms will adhere to the adhesive surface of the paddle or tape.  Parasite Disease Hosts Habitat Enterobius Enterobiasis DH: Man Large intestine vermicularis (Oxyuris) Oxyuriasis (Pin worm) (characterized by nocturnal periodidcity) I.S Mode of infection D.S Lab diagnosis Embryonated eggs Ingestion of food and Eggs in the NIH swab water contaminated perianal area. Scotch adhesive with embryonated tape. eggs. Occasionally adult female Sticky paddle. Handling of worms in the To recover the eggs in contaminated clothes or bed linens. perianal area. the perianal area. Autoinfection Retro-infection (larvae hatch and. 2. Eggs of Ascaris (diagnostic stage) Size: 60 x 40 µ Oval in shape bile stained (brown) with striated wall and containing single fertilized ovum. Have a thick egg shell formed of three layers. Intestinal obstruction by Ascaris  Adult Worm ♂ Adult worm of Trichuris trichiura ♂ or ♀ Adult worm of Trichuris trichiura 2. Eggs of Trichuris trichuria (diagnostic stage) The egg is barrel shaped, bile-stained, has transparent polar prominences. Inside the egg shell, there is a single fertilized ovum.  Adult worm of ♀ Enterobius vermicularis 1. Adult Worm Adult worm of ♂ Enterobius vermicularis Cephalic alae of Male / Female Enterobius vermicularis Coiled Pin at Posterior end Fin-like(cephalic) alae at anterior end  2. Egg of Enterobius vermicularis Diagnostic & infective stage The egg shell is transparent and appears double walled. The egg shell is flat at one side and convex at the opposite side, i.e. plano-convex. Irritation and pruritis ani at night (nocturnal periodicity).