Parasitology Flashcards
What is a host?
organism infected with or fed upon by parasite
What is a definitive host?
adult parasite occurs
What is an intermediate host?
larval development of parasite occurs
How do we pick up parasites?
direct ingestion/inoculation, or by a vector
What is a vector?
an organism that transmits the causative agent or disease from reservoir to host (ex. mosquito)
What is the prevalence of parasitic diseases?
affects millions of people a year
What type of organism are parasites?
found under the eukaryotic, protista (single-celled organism) domain or worms/insects are in animal kingdom
What are the three groups of parasites?
helminths, protozoa, and arthtropods
What are heminth parasites?
macroscopic, worm-like, differentiated tissues, eukaryotic
What are protozoa parasites?
microscopic, unicellular, eukaryotic
What are arthropod parasites?
macroscopic, hard exoskeleton, jointed appendages, eukaryotic
What are the three types of helminths?
nematodes, cestodes, and trematodes
What are nematodes?
roundworms, spindle shaped bodies
What are cestodes?
tapeworms, have head to attach to host and segmented body
What are trematodes?
flukes, leaf-shaped or cylindrical
What are some examples of arthropods?
lice, bed bugs, ticks, fleas, flies, and mites
How do we submit specimen to lab for arthtropods?
fix them in steaming hot water to kill but preserve structure, then preserve in dilute alcohol (50-70%)
What are the four classifications of protozoa?
amoebas, ciliates, flagellates, and sporozoas
What disease/infection do amoebas cause?
amebic dysentery, GI symptoms, meningoencephalitis
What organelles of locomotion do amoebas contain?
pseudopods
How do amoebas reproduce?
binary fission
What disease/infection do ciliates cause?
GI symptoms
What organelles of locomotion do ciliates contain?
cilia
How do ciliates reproduce?
binary fission
What disease/infections do flagellates cause?
Giardiasis, trichomoniasis, chagas disease
What disease/infections do sporozoa cause?
malaria, GI symptoms
What is giardia?
“cutest parasite”, has sucking discs that look like two eyes
How do we transmit giardia?
fecal/oral route, “backpackers disease”; found in contaminated food/water and untreated water (beavers are a source = beaver fever)
Where do we see giardia outbreaks?
areas of poor sanitation or children in daycare centers
What is giardiasis?
giardia attaching to epithelial cells in intestine via sucking disc
What are the symptoms of giardiasis?
diarrhea (very foul smelling), flatulence, cramping, nausea/vomiting, weight loss, chronic infection
What are the two forms of giardia?
trophozoite and cyst
What is the trophozoite form of giardia?
feeding/multiplying, motile, causes symptoms, diagnostic stage when in stool (looks like little old man)
What is the cyst form of giardia?
environmentally resistant, infective stage (oval with up to four nuclei)
What is Entamoeba histolytica?
a pathogenic intestinal amoeba; invasive and can travel to different organs in the body
What is Entamoeba histolytica the 3rd most common cause of?
death due to parasites
What are the two forms of Entamoeba histolytica?
trophozoite and cyst
What is the trophozoite form of Entamoeba histolytica?
the motile, one nucleus, may contain ingested RBC form
What is the cyst form of Entamoeba histolytica?
the infective, up to 4 nuclei form
How does Entamoeba histolytica spread?
contaminated food/water or hands, passed in infective stool
What are the risk groups for Entamoeba histolytica?
men who have sex with men (MSM), travelers and recent immigrants, immunocompromised, and institutionalized populations
What does Entamoeba histolytica do in humans?
often asymptomatic, but can cause amoebic dysentery (bloody diarrhea), extra-inestional infection (migration to other organs)
What is cryptosporidium?
a sporozoa found in fecal specimen, smaller than others and use an acid-fast stain (pink to red color)
What does cryptosporidium cause?
mostly gastrointestinal infections; mild, self-limiting, watery diarrhea without blood
What can cryptosporidium do in HIV/AIDS patients?
high amounts of stools a day lasting months to years leading to tremendous fluid loss
Where is cryptosporidium found?
worldwide in humans and animals
How does cryptosporidium spread?
fecal-oral, anal sex, water-borne transmission, food-borne transmission, (animal handlers, anal sexual contact, and day care participants at high risk)
What are characteristic of nematodes?
long, narrow worms; large range of sizes; separate sexes; development includes 4 larval stages and an adult stage
What is ascaris lumbricoides?
a large intestinal nematode (round-worm), one of the most common; has creamy texture; distributed worldwide with highest in tropics, poor sanitation, and rural southeast US
What is ascariasis?
often asymptomatic; pneumonia, cough, fever; abdominal pain; migrating worms may be expelled via nose or mouth
What is the ascaris lumbricoides life cycle?
1) human ingests egg and larvae hatch in duodenum
2) larvae migrate through intestine into lungs
3) larvae are coughed up and swallowed
4) larvae mature to adulthood in intestine
5) adult females produce eggs
6) infection to maturity takes 50 days
What is enterobius vermicularis?
most common helminth infection in US, “pinworm”; very infectious due to easy transmissibility
What are symptoms of enterobiasis (pinworm infection)?
perianal pruritus (intense itching), mild nausea or vomiting, loss of sleep and irritability, frequently asymptomatic
How is enterobius vermicularis diagnosed?
the “scotch tape preparation”, take a piece of clear tape and put the sticky side near anal opening, plass it down on glass slide and look for the eggs
What do enterobius vermicularis eggs look like?
thick-walled and flattened on one-side
What are characteristics of cestodes?
long, ribbon like worms; vary in length; adults live in intestinal tract and larvae lives in tissues of intermediate host
What is the structure of cestodes?
head/scolex that has sucking disk for attachment, neck that produces proglottids
What is taenia saginata (beef tapeworm) and taenia solium?
cows (saginata)/pigs (solium) are host when undercooked where larvae are present
What are symptoms of taenia saginata/solium?
abdominal pain, nausea, diarrhea, weight loss
What is cysticercosis?
from taenia solium ONLY; human ingests egg and becomes accidental intermediate host, cysterci may develop in muscle, eyes, brain, lungs, and connective tissue
What structures will you see in taenia infections?
eggs with thick walls and radial striations, then T.solium has four suckers with two rows of hooks while T. saginata has four suckers with no hooks
What are characteristics of trematodes?
leaf-shaped flukes rarely seen in US; attach by suckers; blind GI tract; complex life cycle with a long life-span
Where are fluke eggs found?
feces, sputum, and deposited in freshwater
What are fluke intermediate hosts?
first is always water snail, second is either crab, fish or water plant
How do humans become fluke infected?
humans infected by ingesting undercooked/raw crab, fish or water plants
How do we diagnose parasites?
may be clinical based on symptoms, patient history, and travel; or we have some laboratory tests based on travel/immune status (ELISA test)
