Parasitology lecture

One organism benefits while the host is harmed

Parasitism

Protozoa-unicellular
helminths-multicellular, worms
ectoparasites-multicellular, ticks, mites

Classification

capsule like sac that encloses organisms in their dormant or larval stage

Cyst

active feeding stage of protozoan parasite

trophozoite

adult or sexually mature parasite

Definitive/final host

developmental stages

intermediate host

soil, water, vegetation

extracorporeal

>obain 3 stool samples in a 10 day period
>ova and parasites: O&P
>Transportation-liquid is good for 30 min, semisolid 1 hour, formed 24 hour
>Preservatives: 10% formalin-wet mounts, concentration techniques
PVA-polyvinyl alcohol-permanent stains

Parasite specimen collection and handling

10% formalin

What preservative is better for eggs, cysts, and larvae

PVA

What preservative is best for eggs, cysts, and trophozoites

Cellophane tape test, blood, urine, sputum, other tissues

Ways to collect specimen

trophs

Softer consistency more likely contain

cysts

formed consistency more likely to contain

>separate parasites from fecal debris
Useful for recovering eggs, cysts, and larvae
>Trophs are usually destroyed

Concentration techniques

Iodine- protozoan cysts
Trichrome-protozoan trophozoites and cysts
modified acid fast stain-sporozoa

Stain techniques

Human ingests developed egg, larval form hatches in intestine

Nematode life cycle

Pinworm-most common nematode infection in U.S.

Enterobius vermicularis

What worm is this

enterobius vermicularis/pinworm

Most common in children, fecal oral or fecal to any surfaces
Symptoms: perianal itching
Diagnosis: cellophane tape test

Cycle and diagnosis of enterobius vermicularis

Pinworm

What is this egg

Pinworm

What is this adult

whipworm-southern U.S. transmission: ingest infective eggs from soil or on food Adult worms live in colon

Trichuris trichiura

What is this adult

trichuris trichiura/whipworm

what is this egg

trichuris trichiura/whipworm

light infection: asymptomatic
heavy infection: enteritis, diarrhea, rectal prolapse
Diagnostic stage: eggs in feces

Symptoms of trichuris trichiura

"roundworm"
largest intestinal roundworm
Southern U.S.

Ascaris lumbricoides

infective egg from soil or food, larval migration through liver and lungs, adult worms in small intestine
light infection: asymptomatic
Heavy infection: pneumonia, diarrhea and bowl obstruction
Diagnosis: eggs or adults in feces, adults may exit from nose, mouth

Transmission and symptoms of Ascaris lumbricoides

Ascaris adult
NOTE: normally earth worm color this is preserved

What is this

Ascaris fertilized egg

What is this egg

hookworm
infective larvae penetrate host skin
larva migrate through blood and lungs, cough up larva and swallow to bring adults into small intestine

Necator americanus

necator americanus/hookworm

What is this

Hookworm/necatar americanus

What is this egg

trichina worm
ingestion of encysted larva in undercooked meat
Adults live in small intestine, larval migration from striated muscle (diaphragm, eye muscles, arms)
symptoms: gastric distress, fever, muscle pain, eosinophilia- produce a lot of eosinophils

Trichinella spiralis

trichinella spiralis

What are these larvae

look for intact worms, consistency, color

macroscopic examination

protozoa-unicellular

Cysts and trophs are only in what group

wet mount prep: use unpreserved stool, saline prep for motile, iodine prep to enhance detail but can kill trophs, sometimes sealed with nail polish, use low power scanning, high power for suspicious structures

microscopic examination for O&P

separate parasites from fecal debris
flotation, sedimentation

Fecal concentration

use a solution which have a higher specific gravity than the parasites, parasites move to the top and debris sinks to the bottom. Produce cleaner material than the sedimentation technique but eggs and cysts will often collapse

Flotation

use solutions of lower specific gravity than the parasites, parasites fall to the bottom. Easier to perform and less prone to errors but trophs do not survive

Sedimentation

allows for the ID of nuclear detail, size, internal structures

Trichrome staining

cytoplasm: blue/green
Nuclear chromatin, karyosomes, chromatoidal bars, RBC: dark red/purple
Eggs/larvae: red
Yeast/background: green

Trichrome stain

Tapeworm
Adult lives in small intestine
Intermediate hosts: cow, pig, fish
Infective stage: larval form
transmission: ingestion of larval form
Diagnosis: eggs, proglottids, or scolex in feces

Cestode life cycle

what is an example of a cestode

tapeworm, tinea species

segments of the tapeworm body where it absorbs nutrients from our intestines- have male and female reproductive organs

Proglottids

Dwarf tapeworm
ingestion of infective egg in food or water-auto reinfection is common
Light infections: asymptomatic
Heavy infections: abdominal pain, diarrhea

Hymenolepis nana
Transmission
Symptoms

Hymenolepis nana: dwarf tapeworm

What is this egg

beef tapeworm (up to 50 feet long)
cow
larva ingested in undercooked beef
asymptomatic or abdominal pain, diarrhea, weight loss

Taenia saginata
Intermediate host
transmission
symptoms

Pork or beef tapeworm-can't tell by egg but can tell by proglottids

What is this egg

Pork tapeworm (up to 30 feet)
larva ingested in undercooked pork
asymptomatic or abdominal pain, diarrhea, weight loss

Taenia solium
transmission
symptoms

Taenia solium proglottid

what proglottid is this

taenia saginatta

what proglottid is this

Fish tapeworm (up to 60 feet)
crustacean, fish
larva ingested in raw or undercooked freshwater fish
abdominal pain, weight loss, macrocytic anemia due to B12 deficiency

Diphyllobothrium latum
intermediate host
transmission
symptoms

Fish tape worm egg

What is this

What is this

Diphyllobothrium latum fish tapeworm

Fish tape worm proglottids

What is this

Dog tapeworm
We are accidental hosts
infective eggs move to liver or lung

Echinococcus granulosus

What is this

Echinococcus granulosus Dog tapeworm

What is this

Echinococcus granulosus Dog tapeworm

swimmers itch: from fresh water contaminated by duck feces or snails, allergic response to penetration

Schistosoma species-flukes

Schistosoma-swimmers itch

What is this

what is this

Schistosoma haematobium bladder fluke

what is this

Schistosoma egg

Amoeba-motile via pseudopods
Flagellates-have flagella
Sporozoa- non-motile

Protozoan

Amebic dysentery-abdominal pain with bloody diarrhea
ingest infective cysts from fecally contaminated food and water
Trophs in large intestine

Entamoeba histolytica

Entamoeba histolytica troph

What is this

Entamoeba histolytica cyst

What is this

traveler's diarrhea
Watery diarrhea, explosive, foul smelling, malabsorption syndrome
Ingest cysts in fecally contaminated food or water

Giardia lamblia

Giardia lamblia cyst

What is this

Giardia lamblia troph

What is this

vaginitis, urethritis
irritating frothy vaginal discharge in females, males usually asymptomatic
sexual contact
trophs in urethra or vagina, urine

Trichomonas vaginalis
causes
symptoms
transmission
diagnosis

Trich-only if it's moving

What is this

chagas disease
fever, muscle pain, malaise, occur 2-3 weeks after the bite-chronic damage to the heart may occur
Diagnosis: trypomastigotes in blood, amastigotes in heart and other tissues
Xenodiagnosis: examine bugs for organism

Trypanosoma cruzi

Trypanosoma cruiz

What is this

plasmodium vivax-most common
plasmodium malariae
plasmodium falciparum-most severe
plasmodium ovale-rare
Cyclic fever, chills, anemia

Plasmodium species:malaria

what is this

plasmodium ovale

What is this

plasmodium falciparum

what is this

plasmodium malariae troph

What is this

plasmodium vivax troph

Nonpathogenic
Cyst: 1-8 nuclei, eccentric karyosome
Troph: 1 nuclei, ingested bacteria, no RBC

Entamoeba coli

Entamoeba coli troph

What is this

Entamoeba coli cyst

What is this

nonpathogenic, irregular clumped karyosome, no peripheral chromatin

Endolimax nana

acquired from contaminated fruit and veggis, immature oocysts are found in the feces and are 8-10 um

Cyclospora cayetanensis

Cyclospora cayetanensis

What is this

asexual phases in humans in the liver and in the RBC
Route of infection from female anopheles mosquito

Plasmodium malaria

Not as severe
Schuffner's dots
Invade retics (very immature RBC)
12-14 merozoites
gamete fills the cell
48 hour fever cycle

Plasmodium vivax

malignant malaria-most severe
small delicate, double chromatin dots
crescent-shaped gametocytes

Plasmodium falciparum

plasmodium falciparum

What is this

72 hour fever cycle
invades older RBC
band form of troph

plasmodium malariae

RBC has fringed edge
schuffner's dots
resembles vivax

Plasmodium ovale

penetrate intestinal cell, tachyzoite formation, rupture the cells. Can form cysts in tissues of immunocompromised individuals. Can pass onto the fetus

Toxoplasma gondii