Clinical Parasitology PDF

#Bewiththebest #teamSpearhead The Riphilline notes Clinical Parasitology Medical Technology Assessment Program Pa...

#Bewiththebest #teamSpearhead The Riphilline notes Clinical Parasitology Medical Technology Assessment Program Page 1 Topic 1 CLASSIFICATIONS OF HUMAN PARASITES 1. Protozoa NOTE: 4 classes: MOTILITY a. Sarcodina – Pseudopodia (sluggish/slow) b. Mastigophora – Flagella c. Ciliophora – Cilia d. Sporoa – Non-motile e. Miscellaneous classification 2. Nematoda: a. Phasmidea/Aercentea/Phamids – contain the caudal chemoreceptors (posterior) b. Aphasmidea/Adenephorea/Aphasmids – instead have the cervical chemoreceptors (anterior) 3. Platyheminthes NOTE: Number of segments/proglottids a. Cestoda – multiple segments i. 2 orders: UTERINE PORE ii. PSEUDOPHYLLIDEA – None iii. CYCLOPHYLLIDEA – Present b. Trematoda – 1 segment/ unsegmented 4. Arthropoda (vector) a. Insecta – wings b. Arachnida – legs c. Mollusca – shell 5. Pentastomids a. Aka. tongue worms 6. Acanthocephala a. Aka. thorny-headed worms Topic 2 PARASITE-HOST RELATIONSHIPS 1. Type of Parasites a. Obligatory parasite – cannot survive outside of a host b. Facultative parasite – capable of existing independently of a host; may be free-living, may become parasitic when the need arises. c. Endoparasite – established inside of a host d. Ectoparasite – established in or on the exterior surface of a host e. Erratic – a parasite that is found in an organ that is not its usual habitat f. Permanent – remain on or in the body of the host for its entire life g. Temporary – lives on the host for a short period of time h. Spurious – free living; passes through the digesting tract without infecting the host 2. Type of a Host a. Accidental – aka. incidental host; other than the normal one that is harboring a parasite. b. Definitive – the adult sexual phase of parasite development occurs c. Intermediate – the larval asexual phase of parasite development occurs d. Reservoir – harboring parasites that are parasitic for humans and from which may become infected e. Transport – responsible for transferring a parasite from one location to another f. Carrier – parasite-harboring host that is not exhibiting any clinical symptoms but can infect others g. Vector – Arthropoda; transmits the parasite from the arthropod to the susceptible host; can be a biologic or mechanical vector. 3. Parasite-Host relation terms a. Symbiosis – living together; the association of two living organisms, each of a different species b. Commensalism – two different species of organisms that is beneficial to one and neutral to the other c. Mutualism – two different species of organisms that is beneficial to both d. Parasitism – two different species of organisms that is beneficial to one at the other’s expense e. Pathogenic – demonstrated the ability to cause disease 4. Terminologies relating to exposure and infection a. Exposure – process of inoculating an infective agent b. Infection – establishment of the infective agent in the host c. Incubation period – aka. the clinical incubation period; the period between infection and evidence of symptoms d. Pre-patent period – aka. the biologic incubation period; the period between infection or acquisition of the parasite and evidence or demonstration of infection. e. Autoinfection – infected individual becomes his own direct source of infection. i. Enterobius vermicularis – hand-to-mouth transmission ii. Capillaria philippinensis – internal multiplication iii. Hymenolepis nana iv. Strongyloides stercoralis f. Superinfection – aka. hyperinfection; an already infected individual is further infected with the same species leading to massive infection with the parasite. DO NOT REPRODUCE WITHOUT PERMISSION!  #Bewiththebest #teamSpearhead The Riphilline notes Clinical Parasitology Medical Technology Assessment Program Page 2 5. Sources of infection a. Contaminated soil and water are the most common sources of infection i. Water maybe contaminated with cysts of amebae and flagellates (transmission: ingestion) or cercariae (transmission: skin penetration) ii. Favors the development of: 1. Ascaris lumbricoides 2. Trichuris trichiura 3. Strongyloides stercoralis 4. Hookworm b. Food, in particular, undercooked or raw meat/flesh can result in the infection by a number of trematodes and cestodes. i. Raw crabs/crayfish – Paragonimus westermanii ii. Raw Bullastra snails – Artyfechinostomum malayanum c. Arthropods i. Mosquitoes – malaria and filaria ii. Triatoma bugs – Trypanosoma cruzi iii. Sand flies – Leishmania spp. d. Mammals i. Cats – Toxoplasma spp. ii. Rats – Hymenolepis nana e. Fomites – inanimate carriers of infections (e.g., beddings and clothings) f. Asymptomatic carriers – Entamoeba histolytica working as food handlers in food establishments may be important sources. 6. Modes of transmission a. Mouth as the portal of entry: i. Ingestion of contaminated food (i.e., Taenia spp. and Diphyllobothrium latum) ii. Drinking of contaminated water (i.e., Entamoeba histolytica and Giardia lamblia cyst) b. Skin penetration i. Exposure to soil – Hookworms and Strongyloides ii. Exposure to water – Schistosoma c. Vector bite i. Examples: malaria, filariasis, leishmaniasis, trypanosomiasis and babesiosis d. Congenital transmission (aka. vertical transmission) i. Toxoplasma gondii – can cross the placental barrier ii. Ancylostoma and Strongyloides – transmammary infection e. Inhalation (i.e., Enterobius vermicularis and Naegleria fowleri) f. Sexual intercourse (i.e., Trichomonas vaginalis) 7. Epidemiologic measures a. Incidence – number of new cases of infection appearing in a population in a given period of time. b. Prevalence – number of individuals in a population estimated to be infected with a particular parasite species at a given time c. Cumulative prevalence – percentage of individuals in a population infected with at least one parasite d. Intensity of infection – burden of infection which is related to the number of worms per infected person. i. Direct – expelled worm count ii. Indirect – defecated egg count; expressed as eggs per gram (epg) e. Sporadic – a particular disease appearing occasionally f. Endemic – a disease constantly present at some rate of occurrence in a particular location g. Outbreak – a larger-than-normal number of diseased or infected individuals that occurs over a relatively short period. h. Epidemic – a larger-than-normal number of diseased or infected individuals in a particular location i. Pandemic – an epidemic that spans the world Topic 3 SPECIMEN COLLECTION AND PROCESSING 1. Stool a. Most commonly submitted sample in the laboratory b. Ova and Parasites (O&P): the most common procedure in the examination of the stool. c. Comprises of three (3) separate protocols: i. Direct wet smear ii. Concentration technique iii. Permanent stained smear d. Collection and transport i. Typical stool protocol consists of 3 specimens 1. 1st and 2nd day of collection – collect normally 2. 3rd day – using a cathartic agent (MgSO4 and Fleet’s Phospho-soda) 3. For amoebiasis – six (6) specimens in 14 days are acceptable ii. Stool container 1. Best collected in clean, wide-mouthed containers made of waxed cardboard with a tight-fitting lid to ensure retention of moisture and to prevent accidental spillage. 2. Do not contaminate with toilet water or paper. DO NOT REPRODUCE WITHOUT PERMISSION!  #Bewiththebest #teamSpearhead The Riphilline notes Clinical Parasitology Medical Technology Assessment Program Page 3 iii. Amount of stool: 1. Formed stool: Walnut-sized specimen (2-5g) 2. Watery stool: 5-6 tablespoons of watery stool iv. Age 1. Liquid stool: within 30 minutes (to ensure the presence of trophozoites) 2. Semi-formed stool: within 60 minutes (mixture of protozoan cysts and trophozoites) 3. Formed: up to 24 hours Protozoan trophozoites Soft or liquid Cysts Formed Helminth eggs Liquid or formed stool v. Storage 1. Place directly into a fixative at the time it is collected 2. Refrigeration kills trophozoites 3. Never freeze; keep in incubator vi. Certain medications (barium, bismuth, laxatives and anti-diarrheal) may interfere with the detection of parasites 1. These drugs leave crystalline residues that interfere with the identification 2. Stool should be collected prior the therapy or a week (5-7 days) after the last intake of these drugs vii. Antibiotics or antimalarial drugs decrease the number of protozoans for several weeks. 1. Collection should be delayed for 2 weeks following therapy. viii. Urine should not be allowed to contaminate in the stool; it destroys some parasite. 2. Macroscopic examination a. Examining stool for scolices and proglottids of cestodes and adult nematodes and trematodes b. Also reveals the consistency of stool c. The color of stool specimen is noted: i. NORMAL: usually brown ii. BLACK: may indicate upper GI tract bleeding iii. REDDISH: may indicate lower GI tract bleeding; presence of fresh blood 3. Microscopic examination a. Several diagnostic methods can be used in the microscopic examination of a fecal specimen: i. Direct wet mount ii. Concentration procedures iii. Permanent stained smears b. Used for identification of parasite to the species level c. Helpful to identify parasites apart from artifacts 4. Considered as PANIC VALUES: a. STAT when received b. CNS specimens: examined for free-living amoeba c. Blood films: potential malarial case 5. Ocular micrometer a. Disk inserted into the eyepiece of the microscope b. Size is an important diagnostic feature c. Measured as microns Topic 1 Class Rhizopodia PROTOZOAN CLASSES Motility apparatus RHIZOPODIA/ SARCODINA Pseudopods MASTIGOPHORA Flagella CILIOPHORA Cilia SPOROZOA None/Non-motile MISCELLANEOUS Cannot be classified under the four classifications 1. Have protoplasmic processes or pseudopodia 2. All have cystic stage except Entamoeba gingivalis 3. All are commensal except Entamoeba histolytica 4. All are found in the large intestines except Entamoeba gingivalis 5. From among genera, only Entamoeba is considered as true amoeba because the peripheral chromatin is visible in both cyst and trophozoite stages 6. Genus Endolimax and Iodamoeba have neither peripheral chromatin nor chromatoidal bodies 7. ENCYSTATION – trophozoites turning cyst a. Protection b. It has fully eaten c. Large intestines DO NOT REPRODUCE WITHOUT PERMISSION!  #Bewiththebest #teamSpearhead The Riphilline notes Clinical Parasitology Medical Technology Assessment Program Page 4 NOTE: Triggers of encystation: overpopulation, pH change, food supply (too much or too little), available oxygen (too much or too little) 8. EXCYSTATION – cyst turning trophozoite (new offsprings) a. Reproduction b. Small intestines INTESTINAL AMOEBA 1. Unicellular organism 2. Animal like protists 3. No cell wall (outer membrane is periplasts) 4. 2 regions of the cytoplasm: a. Ectoplasm (outer) – contain motility apparatuses – homogenous b. Endoplasm (inner) – heterogenous 5. Contains at least one and some several nuclei 6. With special organs for locomotion - pseudopods 7. Some contain glycogen vacuoles for storage and transport a. Chromatoidal bar/ mass– food storage i. Trophozoite – feeding ii. Cyst – non-feeding b. GLYCOGEN VACUOLES – very observable to Iodamoeba butschlii 8. KARYOSOME – Nucleolus (RNA synthesis) – for specie identification a. Bulls-eye karyosome – E. histolytica (central) 9. Multiplies via binary fission (nuclear and cytoplasmic division) a. E. Histolytica Trophozoite: i. 1 nucleus precyst: 2 nuclei ii. Cyst: 4 nuclei iii. Metacystic trophozoite (new organisms): 8 nuclei DO NOT REPRODUCE WITHOUT PERMISSION!  #Bewiththebest #teamSpearhead The Riphilline notes Clinical Parasitology Medical Technology Assessment Program Page 5 DIFFERENTIATION OF ENTAMOEBAS DIFFERENTIALS Entamoeba histolytica Entamoeba coli Final Host Man Habitat Large intestine Mode of Transmission Ingestion of Infective Stage Pathogenicity Pathogenic Commensal CYST No. of nuclei One to four One to eight Karyosome Small and centrally located Large, irregular shape, eccentric Unevenly distributed, coarse and Peripheral chromatin Finely and evenly distributed granular and irregularly arranged along the nuclear membrane Cytoplasm Finely granular, clean-looking Coarse and granulated, dirty-looking Splinter-like/ witch-broom/whisked Chromatoidal bar Coffin/rod/cigar/ sausage-shaped broom Nuclear membrane Thin Thick TROPHOZOITE Shape Irregular, vary in size and form No. of nuclei One Directional, Unidirectional, Nondirectional, Nonprogressive, Movement Progressive Sluggish Hyaline, Dendritic and finger-like, Shape of pseudopodia Granular, blunt and rounded blunt/extended Manner of release Explosive Several at a time Nucleus 1 karyosome 1 uneven peripheral chromatin Inclusion RBC Vacuoles Finely granular, clean-looking, with Coase and granulated, dirty looking Cytoplasm crystalline-array of ribosomes, usually vacuolated “Ground-glass appearance” PATHOGENESIS AND CLINICAL MANIFESTATION 1. Most cases present as asymptomatic infections with cysts being passed out in the stools (cyst carrier state) 2. The non-pathogenic E. dispar has a higher prevalence than E. histolytica 3. Most E. histolytica infections are asymptomatic in endemic communities 4. Amoebic colitis a. Gradual onset of abdominal pain and diarrhea w/ or w/o blood and mucus in stools b. Fever occurs only in 1/3 of patients c. Intermittent diarrhea alternating with constipation d. Children may develop fulminant colitis i. Severe bloody diarrhea ii. Fever iii. Abdominal pain 5. Amoeboma a. Occurs in less than 1% of intestinal infections DO NOT REPRODUCE WITHOUT PERMISSION!  #Bewiththebest #teamSpearhead The Riphilline notes Clinical Parasitology Medical Technology Assessment Program Page 6 b. Mass-like lesion with abdominal pain and history of dysentery c. Can be mistaken for carcinoma 6. Amoebic liver abscess (ALA) a. Most common extra-intestinal form of amebiasis b. Cardinal manifestations (most frequent complaints in acute cases {2 weeks duration) i. Found in older patients ii. Wasting disease iii. Weight loss rather than fever f. 72% of daily stool cultures harbored trophozoites even in asymptomatic infections g. Mortality uncomplicated