Parasitology Comprehensive exam PDF

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Comprehensive Medical Parasitology

Alvin Rey F. Flores, RMT, MT (ASCPi), MPH Gregorio L. Martin I, RMT MSMT, MPH

Compiled by:

Araceli L. Gumarao Trysha Anne Ysobel C. Gonzalez Samuel H. Orolfo 1

Some characteristics of parasitic diseases ➔ Prevalence in developing countries; in lower Fundamentals of Parasitology socioeconomic population 1. Biological relationships ➔ Low mortality and morbidity - not deadly; ● Symbiosis - relationship between 2 unlike usually neglected organisms ➔ Limited drug-development ○ Symbiont (or symbiote) - organisms ➔ No current vaccines involved in a symbiotic relationship 2. Symbiotic relationships Host ● Species which harbors the parasite ● Mutualism - both organisms benefit ● It may show no harmful effects or may suffer ● Commensalism - one benefits; the other is from the pathogenic effects of the parasite unharmed ● Phoresis - “to carry” ○ No physiologic interaction between the 2 1. Final host - definitive host a. Harbors the mature/adult form of the parasite organisms - only carries the organism; b. Where sexual reproduction will happen nothing happens c. Ex. man - usually the definitive host ○ Phoront - the organism being carried 2. Intermediate host ■ Always the smaller organism a. Harbors the immature/larval form of the ○ Ex. cockroach (host) and Ascaris egg parasite (phoront) b. sWhere asexual reproduction will happen ● Parasitism - the parasite benefits; the host is c. ex. Lower animals, vegetation, insects, man harmed (Plasmodium - malaria) Parasitology 3. Vectors - responsible for transmission of the ➔ An area of biology that deals with the dependence parasite of one organism on another a. Biological vector - morphologic change or ➔ Study of parasites, its hosts and their relationships transformation of the parasite before ➔ Host transmission to another host ➔ Parasite i. There would be physiological development of the parasite inside the Parasites: A Public Concern biologic vector ➔ Millions of people are affected worldwide ii. The parasite is always inside the biologic ➔ Mostly in poor, developing countries (most are vector tropical countries) iii. Ex. Aedes mosquito, Tse tse flies, Ticks PARASITOLOGY LECTURE INTRODUCTION

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b. Mechanical/Phoretic vector - no development c. Ex. free living pathogenic ameba occurs on the parasite 3. Commensal - non pathogenic i. The parasite is found outside the a. Ex. Entamoeba coli mechanical vector ● Parasites accdg to habitat: ii. Ex. cockroaches and flies 4. Accidental host - harbors a parasite that usually 1. Ectoparasite - found outside the host a. Infestation - presence of a ectoparasite in a does not infect it host a. Man becomes an accidental host of animal b. Ex. Ticks, Lice, Fleas parasites 2. Endoparasite - found inside the host b. Ex. man a. Infection - presence of an endoparasite in a i. Toxocara canis - ascaris of dogs host 5. Paratenic host - “transfer host” b. Most parasites are endoparasite a. Harbors the larval stage but no other 3. Erratic parasite - parasite not living in its natural development happens habitat (organ of the body) b. Ex. boars - paratenic host of Paragonimus a. Ex. Ascaris - normally lives in the small westermani intestine, if found on another part of the body 6. Dead-end host - incidental host; does not anymore - considered as erratic parasite allow the life cycle of the parasite to continue a. Ex. humans - Trichinella spiralis (parasite of 4. Accidental/Incidental parasite - parasite that does not lie in its usual host pigs; eating of undercooked pork; larva would a. Ex. Toxocara canis - if found in humans eventually be deposited in the muscle of considered as accidental parasite humans; only affects mammals) 7. Reservoir host - host other than parasite’s usual 5. Spurious parasite - free living organism that passes through the GI tract without infecting the host that allow the life cycle to continue host a. Animals that can continue the life cycle of 6. Temporary parasite - transient parasites parasites even in the absence of humans b. Ex. pigs (Balantidium coli), field rats (Paragonimus westermani), cats (Brugia ● Parasites accdg to egg laying capacity malayi), beavers (Giardia lamblia - beaver 1. Oviparous parasite - laying immature eggs a. Egg is not yet embryonated; no larva present fever) inside the egg b. Ex. A. lumbricoides, T. trichiura, E. Parasite vermicularis 1. Obligate - parasite that always require a host for it to survive 2. Ovoviviparous laying mature eggs a. Most parasites are obligate (embryonated; presence of larva inside the egg; b. Ex. Ascaris lumbricoides, Hookworms, segmented eggs) Trichuris trichiura a. Ex. Schistosoma, Clonorchis sinensis 3. Larviparous - larva laying parasites 2. Facultative - free living and a parasitic phase a. T. spiralis a. Usually free living but if the environment is no longer favorable, it becomes parasitic b. Ex. Threadworms (Strongyloides stercoralis ● Parasites accdg to sexes 1. Monoecious - hermaphrodite - smallest nematode) 3

a. Both testes and ovaries are found in one Exposure and infection parasite ➔ Pathogen b. Ex. flukes and tapeworms ➔ Infection 2. Dioecious - M/F ➔ Carrier a. Ex. all nematodes, Schistosoma 3. Parthenogenetic - female parasites capable of cell ➔ Incubation period - period between infection and appearance of signs and symptoms fertilization ➔ Pre-patent period - period between infection and a. Ex. female worms of S. stercoralis evidence/demonstration of infection ➔ Autoinfection - infected individual becomes ● Parasite stages his/her own source of infection 1. Helminthes ◆ Ex. Capillaria, Strongyloides, Enterobius, a. Adult Cryptosporidium b. Larva ➔ Superinfection/Hyperinfection infected c. Egg/Ovum individual is further infected with the same 2. Protozoans parasite a. Trophozoite ◆ Ex. Strongyloides b. Cyst Epidemiology ● Transmission of parasites ➔ Prevalence 1. Soil Transmitted Helminthes ➔ Cumulative prevalence a. Hookworms, Ascaris lumbricoides, Trichuris ➔ Incidence trichiura, Strongyloides stercoralis ➔ Sporadic 2. Vector borne ➔ Endemic a. Ex. Plasmodium, Hemoflagellates, Filarial ➔ Epidemic worms ➔ Pandemic 3. Food borne ➔ Elimination a. Ex. Fasciola, Opisthorchis, Clonorchis, ➔ Morbidity Echinostoma, Heterophyes, Taenia ➔ Intensity of infection 4. Water borne a. Ex. G. lamblia, Cryptosporidium Some characteristic of parasitic diseases 5. Vertical transmission ➔ Morphology a. Ex. Toxoplasma gondii ➔ Geographic distribution 6. Transmammary ➔ Life cycle a. Ex. Ancylostoma, Strongyloides ➔ Symptoms 7. Inhalation ➔ Pathogenesis and immunity a. Ex. Enterobius ➔ Diagnosis 8. Intimate contact ➔ Treatment and prevention a. Ex. Trichomonas vaginalis ● Life cycle 1. Direct 2. Indirect

What are the harmful effects of the parasites to human hosts? ➔ Some organisms may infect humans but do not cause disease 4

➔ Parasites can cause injury by release of v. Ex. Enterocytozoon and Encephalitozoon metabolites/enzymes ➔ Parasites can cause invasion and tissue d. Phylum aschelminthes - Class Nematoda destruction e. Phylum Platyhelminthes ➔ Parasite can deprive certain nutrients from hosts i. Class Trematoda ➔ Tissue damage 1. Order Digenea ◆ Ex. fatty degeneration, albuminous ii. Class Cestoda degeneration, necrosis Laboratory diagnosis ➔ Tissue changes ◆ Ex. hyperplasia, hypertrophy, metaplasia, Stool: ● Most common specimen submitted neoplasia ● Different parasite stages can be detected in stool sx ● Container used: wide mouth water tight plastic Effects of the host on the parasite container with lid ➔ Genetic makeup of host ● Number of stool collections: ◆ Ex. Duffy Blood Group Fy(a- b-) ○ Usually 3 sx in a span of 10 days ➔ Nutrition and diet ○ Up to 6 sx collected in 14 days for detection of ◆ Ex. high protein diet amebiasis ➔ Immunity and immune response ● Amt of stool sx: ○ 2-5 grams of formed stool Parasite evasion mechanisms ➔ Resistance to immune response ○ 5-6 tablespoons for loose or diarrheic stool ➔ Immune suppression ● Specimens can be received in fresh or preserved ➔ Antigenic variation (VSGs, VSP) ● Preservatives ➔ Host mimicry - Echinococcus granulosus larva ○ Fixed ratio = 3:1 ➔ Intracellular sequestration ■ Formalin ■ MIF ● Medically important parasites ■ PVA with Scahudinn’s 1. Protozoans (Kingdom Protista) ■ SAF a. Phylum Sarcomastigaphora ● Examination i. Subphylum Sarcodina - amoeba ○ O and P examination ii. Subphylum Mastigaphora - flagellates ■ Macroscopic examination iii. Subphylum Ciliophora - ciliates ● Stool consistency b. Phylum Apicomplexa ● Color i. Class Sporozoa ● Gross abonormalities ii. Suborder Haemosporina ○ Microscopic examination iii. Suborder Eimeria ■ Direct wet mount c. Phylum Microsporidia ● NSS mount i. Intracellular parasites ● Iodine mount ii. Now classified as fungi ● Concentration technique iii. Spore forming ○ Sedimentation iv. Possess polar tube ○ FECT ○ AECT 5

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○ Flotation ■ Brine flotation ■ Zinc sulfate flotation ■ Sheather’s sugar flotation Permanent stains ○ Final procedure ○ Use: confirmation of the presence of protozoan cyst and/or trophozoite ○ Preservation of choice: PVC with Schaudinn’s Common stains ○ Trichome (Wheatley modification) ■ Widely used; easy to prepare; long shelf life ○ Iron Hematoxylin ■ Time consuming; excellent morphology of intestinal protozoans Specialized staines ○ Modified acid fast stain Other examinations done using stool: ○ Kato-Katz ○ Kato-Thick ○ Recovery of Hookworm and Strongyloides larva ■ Baermann technique ■ Coproculture ■ Harada Mori technique ○ Use of culture medium

● Sigmoidoscopy - for E. histolytica ● Cellophane tape preparation - pinworm and Taenia eggs ● CSF - Toxoplasma ● Tissue specimen ● Sputum - P. westermani, Ascaris ● Urine - S. haematobium, T. vaginalis ● Eye specimens - Acanthamoeba, Loa loa ● Mouth scrapings - E. gingivalis, T. tenax ● Nasal discharge - Naegleria ● Skin snips - O. volvulus

Blood: ● Collected for diagnosis of systemic or blood borne parasites ● Examinations done ○ Thick and thin smears ○ Knott’s concentration technique ■ 1mL + 10mL 2% formalin ○ Buffy coat slides Other sx: ● Duodenal material - for Giardia, threadworm, Cryptosporidium 6

PARASITOLOGY LABORATORY INTRODUCTION List of Parasites: 1. Nematode - roundworms 2. Trematode - flukes 3. Cestodes - tapeworms 4. Protozoans

● Copulate (hermaphrodites) ○ Expt cestodes (not dioeceous) ○ Nematodes = M/F/dioeceous ○ Trematodes = M/F/hermaphrodites ● Eggs are formed ⇒ found in stool Protozoans ● Cyst can be in stool ● Watery = trophozoite in stool

Life cycle: WHO types of stool: 1. Egg ⇒ Larva ⇒ Adult = nematode, trematode, cestode 2. Trophozoite ⇒ Cyst = protozoan a. T ⇒ C = encystation b. C ⇒ T = excystation FORMED FOOD (MOT: ingestion) ⇓ EGG & CYST EGG ⇓ LARVA ⇓ ADULT ⇓ EGGS (stool)

CYST ⇓ TROPHOZOITE ⇓ C/T (stool)

In STOOL: ● Egg ● Trophozoite ● Cyst

SOFT

Cyst ⇓ ● Stable at 3-4 hrs & 24 hrs

LOOSE

WATERY

Troph ⇓ ● Easily disintegrate ● Need to process w/in 30 mins

Stool/day = 24 g Stool sx = 20-40 g; thumbsize; 5-6 scoops Label = name, date and time >1 stool/day = diarrhea Direct fecal smear

Egg, larva and cyst ● Protein/lipid in nature ● Not destroyed in mouth ● Not destroyed by HCl in stomach Larva and Trophozoite ● Motile stages ● In small intestine (duodenum) ⇒ breakdown of egg and cyst (proteases affect the lipid/protein) Adult

● Poke the sx w/ applicator stick 3x in the central area (preferably w/ mucus/blood) ● One drop of NSS in unstained and 1 drop of Lugol’s I2 in stained ● Emulsify first in unstained, then stained ● Cover with coverslip ● Use only one sx 7

● Microscope = HPO Unstained: ● Normal Saline Sol’n ● 0.85 - 0.9 % NaCl ● Used to see trophozoite

Stained: ● Lugol’s I2 ● KI2 + I2 + H2O ● ╳ not see trophozoite ● Cyst is highlighted (can see nuclear details)

Nuclear details = separates the cyst and trophozoite (stained) ╳ too thick = hardly see parasites ╳ too thin ╳ overfilling = sx move in microscope exam Discouraged if refrigerated = other stages are not found

● Divides by binary fission ● Stained using Methylene blue ● Locomotor apparatus: ⇓ 1. Pseudopod = amoebic, “false feet” 2. Flagella = flagellate 3. Cilia = ciliate, “hairlike structures”

● Round bodies (w/ nuclear structures) ● Chromatoidal bar = ✔NSS; not always visible; for food preserve

Round bodies w/out nuclear structures = oil droplet Round bodies w/out nuclear structures and thick surrounding = air bubble Locomotor apparatus: 1. Pseudopod: a. Entamoeba histolytica = amoebiasis i. “Ent” = intestinal (colon) ii. “Histo” = tissue iii. “Lytica” = lysis ➔ examine systematically: can see egg, larva, cyst iv. = capable of tissue lysis = ulcerate intestinal tract PROTOZOAN v. Only pathogenic Egg > adult = more dangerous (IS) vi. Diarrhea w/ blood = dysenteric w/ ATE = egg (others = larva); has infected egg mucus (amoeba = mucus prod’n) ● Ascaris lumbricoides b. Entamoeba coli ● Trichuris trichiura 2. Flagella: ● Enterobius vermicularis a. Giardia lamblia 3. Cilia: Do not encyst ⇒ IS: trophozoite a. Balantidium coli = largest protozoan of ● Trichomonas spp medical interest ● Entamoeba gingivalis Mononucleated trophozoite ● Dientamoeba fragilis ⇓ Mononucleated cyst Encystation = for protection ⇓ Divides to 2 nuclei ⇓ Trophozoite Cyst Divides to 4 nuclei... ● Motile ● Stable 8

Entamoeba histolytica

Entamoeba coli

Trophozoite Pseudopod

● Release 1 egg at a time ● Unidirectiona l progressive

Nucleus

● “Bull’s eye” ● Centrally located karyosome (distinct)

Inclusio n

● RBC = only ingested ➔ “Hematopha gus trophozoite” ➔ From ulceration of intestinal mucosa “Clean looking cytoplasm”

● 2 branching pseudopod ● Several direction at a time ● nondirectiona l Eccentric karyosome

● Bacteria ● Yeast ● Debris

E. COLI = can divide upto 8 nuclei ● There could be a problem in diagnosis if the parasite seen has 4 nuclei (can be seen as E. HISTOLYTICA) ● ╳ chromatoidal bar is not visible sometimes ● To differentiate = look at cystic wall (adjust the fine adjustment knob) Giardia lamblia Trophozoite Parts

Nucleus

● 2 nuclei

Motility

Falling leaf motility “Old man’s face w/ an eyeglass” Giardia lamblia Mature Cyst

“Dirty looking cytoplasm”

Part Nucleus

Entamoeba histolytica

● 4 pairs of flagella ● 2 ventral sucking disc ● Axostyle = divides in 2 equal parts

● Axostyle = divides in 2 equal parts ● 4 nuclei

Entamoeba coli Balantidium coli

Mature Cyst Nucleus

Cystic wall Chromat oi-dal bar

● 4 nuclei = quadrinucleated; tetranucleated ╳ NSS ✔ I2 Thin walled Sausage/cigar shape

Trophozoite 8 nuclei = octonucleated

Parts

* >4 = E. COLI

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Cilia Vacuoles Cytostome = mouth Cytopyge = anus

Nucleus

● Macronucleus = asexual ● Micronucleus = DNA, sexual

Motility

Thrown ball motility/rolling motion

Thick walled Witchbroom w/ splintered ends

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Balantidium coli Mature Cyst Part

Nucleus

● Cilia = enclosed in cystic wall ○ Not motile ● Sometimes vacuoles are visible ● Macronucleus ● Micronucleus

Other substance in stool: artifacts/parasite confuser 1. Food remnants: a. Vegetable fiber = larva like b. Vegetable fiber = spiral c. Muscle fiber = means deficient i. Too much = creatorrhea 2. Blastocystis hominis = parasite - large vacuole; 2-4 nuclei towards the periphery (pushed by vacuole)

PATASITOLOGY LECTURE PROTOZOANS ● Unicellular organisms ● Vary in shape, size, locomotion ● Reproduce asexually or asexually and sexually ● Do not possess a cell wall ● Consists of nucleus and cytoplasm ○ Nucleus: genetic material ■ Contains nucleolus or karyosome or endosome ○ Cytoplasm: 2 regions: ■ Endoplasm ■ Ectoplasm *entamoeba = with peripheral chromatin Subphylum Sarcodina - ameba ● Possess pseudopodia - “false feet”; for locomotion ● Inhabit the large intestine/colon expt E. gingivalis (mouth/oral cavity/gum) ● Entamoeba possess peripheral chromatin ○ Vesicular nucleus - “vesicular” = has spaces/holes inside the nucleus ● All are commensals expt E. histolytica ● Stages of development ○ Trophozoite ■ Motile and vegetative stage ■ Seen in watery/loose stool ■ Labile structures in the absence of water: unstable ■ Stain: to visualize the nuclear details of trophozoite ● Nair’s Methylene Blue or Buffered Methylene Blue ● Quensel’s Methylene Blue ○ Cyst ■ Non motile stage ■ Resistant or stable ■ Round or circular in appearance ■ Most cases of amoeba: MOT is ingestion of cyst ■ Seen in formed stool ■ Stain: Iodine stains 10

● Lugol’s Iodine stain ● D’Antoni’s stain ● Both stains are not used for trophozoite: Iodine is toxic to troph ● The stains are used in a permanent stained smear (not in DFS) Entamoeba histolytica ● Only pathogenic member ● Habitat: Large Intestine ● Final host: Man ● MOT: Oral-fecal or ingestion of infective cyst ● Cyst: ○ 5-16 micrometers ○ Thin wall hyaline (clear, refractile) appearance ○ Up to 4 nuclei (not always 4) ■ Centrally located karyosome = small; inside the nucleus ■ Fine, evenly distributed peripheral chromatin ○ Chromatoidal bar = food reserve and energy source ■ Composed of crystalline RNA ■ Sausage or cigar shape ○ Infective or mature = quadrinucleated ○ Stages: ■ Pre cyst = immature type

■ Metacyst = mature ● Trophozoite: ○ 1 nucleus ■ Centrally located karyosome

■ Fine, evenly distributed peripheral chromatin ○ Ingested RBC = “hematophagus” parasite/trophozoite ■ Greenish structures in DFS (RBC) ○ “Clean looking” cytoplasmic membrane ● Pseudopodia: ○ “Finger like” appearance

○ Unidirectional progressive Ingestion of infective cyst (quadri) ⇓ Stomach ⇓ Small intestine = where excystation happens ● The pH should be alkaline or neutral ● If acidic, it would not excyst ⇓ Large intestine = where multiplication of troph happens ● Via binary fission (4 are produced; 4 nuclei) ● Can destroy the lining of the large intestine ⇓ Stool = troph and cyst can be found; it depends on the consistency of the stool Disease manifestations: 1. Asymptomatic carrier state - majority of cases (90% = unknowingly they are carriers) a. Excrete cyst 2. Symptomatic or Intestinal disease = 10% a. Incubation period: 1-4 weeks b. S/S: bloody diarrhea/dysentery, abdominal pain, flatulence, weight loss, chronic fatigue 11

c. Release of enzymes to lyse mucosal lining d. Formation of flask shaped ulcers = mucosal erosion and crater formation i. Caused by the trophozoite ii. ➔ Clinical forms of intestinal amebiasis: ◆ Dysentery or blood diarrhea - majority of cases ◆ Excessive amounts of mucus in stool ◆ Tenesmus = pain in defecating but no stool is produced ◆ Flatulence = excessive farting ◆ Up to 10 bowel movements/day ◆ Fulminating colitis (inflammation of the colon) ◆ Amebic appendicitis ◆ Ameboma = granulomas (chronic inflammation) ● Can be mistaken as carcinoma (cancer) 3. Extra-intestinal disease - hepatic a. Ectopic form of amebiasis b. Usually occurs in the liver (upper lobe) = Amebic Liver Abscess (ALA) i. Cardinal signs - fever, right upper quadrant pain (where liver is found) ii. Other signs include - tender liver (if palpated, painful) and hepatomegaly (enlargement of liver) iii. Sx = liver aspirate 1. Color = anchovy sauce 2. Trophozoite can be found c. Cutaneous amebiasis or amebiasis cutis = rare complication i. If the parasite causes rupture, can be found in skin ii. Usually in inguinal areas iii. Sometimes associated with venereal infections = STD d. Lung abscess = parasite can also be found in the sputum sx

e. Brain abscess *in amebiasis = no abundant WBC in the stool or low WBC in the stool Pathology: ● Ability to lyse tissues ● Attributed to its virulen...