Parasitology

What is a parasite?

an organism that lives on or in a host at the expense

What is a definitive host?

organism foes through sexual multiplication phases

What is an intermediate host?

larvae and asexual stages are found

How are parasites transmitted?

food and water transmission

Describe an amebae

asexual reproduction, moves via pseudopodia, contains trophozoite and cyst stages

Describe a flagellate

asexual reproduction, moves via flagella, contains trophozoite and cyst stages

Describe a ciliate

sexual reproduction, moves via cilia, contains trophozoite and cyst stages

Describe a sporozoan

can undergo both asexual and sexual reproduction

Describe a roundworm

can be free living or requires an intermediate host and has an egg, larvae, and adult life stage

What are the two types of flatworms?

tapeworms and flukes

What are tapeworms?

ribbon-like hermaphrodite organism that has an egg, larvae, and adult like cycle

What is utilized as an intermediate host for tapeworms?

mammals and insects

What is a fluke?

hermaphroditic and has an egg, miracidium, cercaria, and adult life cycle

What is utilized as an intermediate host for flukes?

fish, snails, and crabs

What are unicellular protozoans?

amebae, flagellates, ciliates, sporozoans

What are multicellular helminths?

roundworms, flatworms

What are the two stages of a protozoans?

trophozoites and cysts, but sometimes they only have a trophozoite stage

Describe the trophozoite stage

motile, replicates, feeds

Describe the cyst stage

immobile, resistant, infective, does not reproduce

Where do protozoan trophozoites live?

intestinal tract

How are trophozoites transferred?

cyst form

How do amebae enter the body?

directly through the mucosal membrane as Trophozoites

How are protozoans identified?

life stages, size, number of nuclei

How are protozoans treated?

metronidazole

Describe the process of Entamoeba histolytica entering and leaving the body

ameba is ingested as a cyst and becomes a Trophozoite in the intestine where it undergoes asexual reproduction in the colon

What happens when a Trophozoite is passed through the stool?

dies from the harsh enviornment

What causes hepatic abscesses?

Trophozoite (Entamoeba histolytica)

What is Naegleri fowleri?

free-living brain eating amoeba

How does someone acquire Naegleri fowleri?

warm water forcefully penetrating the sinuses and traveling to the olfactory nerve to the brain

How is Naegleri fowleri diagnosed?

autopsy in presence of Trophozoites in the brain

Where does Acanthamoeba keratitis cause infections?

cornea

Who is at risk of getting Acanthamoeba keratitis?

people who wear contact lenses, rinse them in tap water, or a failure to disinfect lenses

What disease does Giardia lamblia cause?

gastroenteritis and travelers diarrhea

How does a trophozoite from Giardia lamblia appear?

has falling leaf motility

How is Giardia lamblia transmitted?

drinking contaminated water that contains cysts

What does Trichomonas vaginalis cause?

STIs, specifically purulent vaginal discharge in females and thin urethral discharge in males

How are samples suspected of Trichomonas vaginalis cultured?

Diamonds media without a cyst stage

What are 2 types of flagellates?

Giardia lamblia, Trichomonas vaginalis

What is special about the life-cycle of sporozoans?

complex life cycles involving asexual and sexual reproduction

Where do sexual cycles occur?

definitive hosts

Where do asexual cycles occur?

intermediate hosts

What does Toxoplasma gondii cause?

affects fetuses, mild or mimics mononucleosis

Who is most at risk of Toxoplasma gondii?

immunocompromised and congenital patients

How is Toxoplasma gondii transmitted?

ingesting Oocyt from a definitive hosts fecal route (normally cats), organ transplants

How is Cryptosporidium parvum transmitted?

human to human zoonosis

What is special about Cryptosporidium parvum?

very resistant to chlorination and temperature as the oocysts are thick walled and spherical so it is also acid-fast staining

What are two examples of sporozoans?

Toxoplasma gondii, Cryptosporidium parvum

What is special about helminths?

they have a complex life cycles involving two or more hosts so the adult worms produce eggs and the eggs mature in other species

What are some examples of helminths?

flat worm, roundworms

What are flukes?

dorsoventrally flat and hermaphroditic with leaf-like shapes

How are blood flukes transmitted?

skin penetration from contaminated water while swimming

What are Schistosoma species?

different from other flukes, cylindrically shaped, lack operculum, and have a spike on one end

What do blood flukes cause?

swimmer's itch

What are Diphyllobothrium latum?

found in fish and ingested in pickled-raw freshwater fish, have operculum on their eggs

What are Taenia saginata?

beef tapeworm

What are Taenia soliunm?

pork tapeworm

How is laboratory identification done for flat worms?

using the proglottids or visually through the egg size, colour, and presence of operculum

What are 5 examples of roundworms?

Enterobius vermicularis, Trichuris trichura, Ascaris lumbricoides, Hookworms, Strongyloides stercoralis

How do Enterobius vermicularis appear?

colourless eggs easily seen under 10x, oval, thick shelled, flattened on one side

How do Trichuris trichura appear?

ovum is found in stool and the worm looks like a whip

How do Ascaris lumbricoides appear?

round and bumpy egg, intestinal roundworm (female is largest overall) and larvae can migrate into the trachea and lungs

What causes hookworms?

Necator americanus (New World), ecator americanus (Old World)

What are Strongyloides stercoralis?

very small and threadlike transmitted through infected soil

How are roundworms diagnosed?

checking for anti-strongyloides antibodies, sputum samples looking for worms

What is squiggly bacterial growth an indicative of?

Strongyloides infection

What is the ideal sample of intestinal parasite?

preserved fecal specimens examined within an hour of collection

What is OMP?

sample for ovum and parasite

Describe the OMP

formalin fixative and used to avoid disintegration and from that we do stains, wet mounts, and concentrates

When are stool specimens rejected?

when contaminated with urine or water

Describe specimen collection procedure for suspected parasites

three specimens are collected and spread over 10 days with no collections on the same day

What is a direct wet mount used for in parasitology?

trophozoites and helminth egg identification only

Describe how a direct wet mount is prepared

small amount of fecal specimen is emulsified into a drop of iodine solution or saline and it is cover slipped, sealed with nailpolish, later the iodine will highlight internal parasite structure, destroy trophozoite motility, and stain glycogen

What is the advantage of a direct wet mount?

detects parasites that do not concentrate well

What is the disadvantage of a direct wet mount?

eggs, cysts, and trophozoites can be low in number or confused with fecal debris

What is a concentrate used for?

identifying protozoan cysts, oocyts, helminths eggs, and larvae

How is sedimentation used for parasitology?

uses a lower S.G. then the parasites, ethyl alcohol dissolves fats and formalin fixes and preserves specimens, which is then centrifuged to concentrate the parasites to ID them

How is flotation used for parasitology?

parasites float to the tube as the solution is a lower S.G. then the parasites, if the parasite has a larger ovum with a S.G. greater than 1.300 it sinks to the bottom

Why must tubes used for flotation be examined quickly?

to avoid organisms settling at the bottom of the tube over time

What are permanent stains?

made from concentrates providing contrasting colors from debris and parasites, used to provide organism morphology, trophozoites, iron hematoxylin, or Trichome stain

When is 100x able to be used for smears?

thin areas can be viewed for 10-15 minutes but oil cannot be used to avoid an oil bridge

What is the Iron hematoxylin stain?

used for parasitic structures but has significant variability

What is the trichrome stain?

stains the cytoplasm of cysts and trophozoites blue-green and purple to ID them (RBCs and nuclear chromatin are red-purple with green background)

What is the cellophane tape test used to identify?

Enterobius vermicularis

Describe how the cellophane tape test is used

a sticky paddle is placed on the surface of the anus to collect eggs of pinworms

What parasitic organisms are normally seen in the urine due to fecal or vaginal contamination?

Trichomonas vaginalis, Enterobius vermicularis, Schistosoma

What is special about the organisms Trichomonas vaginalis, Enterobius vermicularis, and Schistosoma?

ovum of these organisms are transparent and possess a delicate terminal spine

What organisms are seen on sputum samples?

Strongyloides, Ascaris lumbricoides and hookworm

How is QA done in parasitology?

updated procedural manuals, control stains, recording of centrifuge calibration, ocular micrometer, calibration, other materials

What are ectoparasites?

parasites that live in or on the skin receiving nourishment through the blood

What are examples of ectoparasites?

ticks, fleas, bedbugs, lice, mites