Parasites Flashcards
In a protozoa what is the name of the replicating form and the inactive form?
Replicating form is trophozoite
Inactive is cyst
What are the four types of protozoa? How are they classified?
Amoebas, Flagellates, Ciliates, Sporozoans
Classified by locomotion
What parasites covered in class are amoebas?
E. histolytica
What parasites covered in class are flagellates?
Giardia, Trichomonas vaginalis, T. cruzi, Leishmania
What parasites covered in class are sporozoans?
Plasmodium
How are protozoa and helminthes different?
Protozoa are single celled, microscopic, eukaryotes
Helminthes are multicellular, macroscopic and have organ systems and reproductive systems
What are the classes of helminthes? How are they classified?
Cestodes (tapeworms), Nematodes (roundworms),
Classified according to structure
What kind of genetic traits give someone protection from P. falciparum?
HbS and HbC (in heterozygous and homozygous state)
What kind of genetic trait gives some protection to P. vivex? What has this resulted in with the predominant form of malaria?
Lacking a Duffy RBC antigen is resistant to P. vivex infection
Shift to P. falciparum being the predominant form f malaria
What is the vector for plasmodium? What cells are the first to be infected? What happens when these first cells to be infected burst? What cells are infected second?
Mosquito- injects sporozoites when bite
Infect hepatocytes first then burst and release merozoites into the bloodstream. Infect RBC second
What is the malaria paraoxysm? How long does it typically last?
Cold stage, Hot stage, Sweating stage, followed by fatigue- typically lasts 6-10 hours but timing differs by species
What makes P. falciparum more fatal than the other plasmodium?
Can infect RBC of all ages, leads to expression of PfEMP-1 on infected RBC which allows it to bind to endothelium causing blockage and ischemia
During pregnancy what do RBC infected with P. falciparum bind to?
Chondroitin sulfate A (CSA) on the placenta
What is the vector for leishmanias?
Sand fly
What are the three different forms of leishmanias? How long after bite do they appear?
Cutaneous: skin sores, weeks afer bite
Visceral: internal organs, potentially life-threatening, months after bite
Mucosal: less common- can be from same species causing cutaneous
What parasite causes American trypanosomaiasis?
T. cruzi
What vector transmits T. cruzi? What is the mechanism?
Triatomine insects (aka kissing bugs)- get the parasite when mucus membrane, conjunctiva, or breaks in skin get infected with bug poop
What are the symptoms of Chagas disease? What parasite causes Chagas?
Acute: fever/swelling around the site of inoculation- usually eye
Can develop heart problems leading to sudden death, or an enlarged esophagus and colon leading to problems eating; T. cruzi
How are babesia transmitted to humans? Is it direct transmission?
Zoonotic disease- reservoir in one vertebrate that is then transferred to a invertebrate vector before infecting humans
Indirect transmission
What is the vector for babesia? What cells are infected?
Ticks; RBC
What are the symptoms of babesia?
Non-specific, flu-like; if symptomatic
What is the most commonly diagnosed enteric parasite in the US?
Giardia
How is giardia transmitted?
Direct ingestion of giardia cysts in contaminated water, person-to-person, or foodborne transmisison
What the stages and symptoms following giardia infection?
Asymptomatic cyst infection, acute self-limited diarrhea, and chronic diarrhea, malabsorption and weightloss
How is giardia diagnosed?
Express cysts in stool; detection of giardia antigen in stool
What is the second most common parasitic infection in the US?
Cryptosporidium
How is cryptosporidium transmitted? Where is it found?
Ingestion of oocysts- found in contaminated water
Where do outbreaks of cryptosporidium arise? Why?
Swimming pools because resistant to chlorination and tied to fecal contamination
What are the symptoms associated with cryptosporidium? When do they begin?
Watery diarrhea (avg 7 days after infection) Diarrhea lasts for 1-2 weeks and then if healthy gets cleared
How is E. histolytica transmitted? What is the disease is causes?
Ingestion of cysts from contaminated water (contaminated with human fecal matter)
Causes amebiasis
How is E. histolytica severe/life-threatening?
Can cause liver abscess- manifesting either acutely (with severe pain) or subacutely (with weight loss and abdominal pain)
What is the most common manifestation of E.histolytica?
Diarrhea without dysentery (inflammation)
How is Trichomonas vaginalis transmitted? Who is the natural host?
STD, humans are the natural host (direct transmission)
When symptomatic, what symptoms do women infected with Trichomonas vaginalis express? What other infections have similar symptoms?
Vaginal discharge and irritation; discharge has an odor and there’s edema/erythema; candidiasis and bacterial vaginosis have similar symptoms
What is the most common helminth infection worldwide?
Ascariasis
Where do ascariasis worms mate?
Lumen of the small intestine
How is ascariasis transmitted? What is it’s life cycle?
Eggs are ingested/inhaled and hatch in the small intestine, releasing larvae, larvae penetrate intestinal wall, travel to lungs, heart and then lungs, break into alveoli, coughed out and then swallowed, to return to the intestines where mature
What are the symptoms of Ascariasis?
Most are asymptomatic; some people get pulmonary involvement, others can cause obstruction of bowel
What are the other names for hookworm?
Ancylostoma dudodenale or Necator americanus
In what areas do hookworm infections normally occur?
Areas where human feces are used as fertilizer
How is hookworm transmitted? What is it’s life cycle?
Eggs are passed in stool and into soil, under favorable conditions hatch releasing rhabditiform larvae,which mature in soil; on contact penetrate human skin and carried through blood vessels to heart and lungs, penetrate alveoli, coughed and swallowed, go to intestine for maturation
What is another name for pin worm?
Enterobiasis or Enterobiasis vermicularis
How is someone infected with pinworms?
Ingest pinworms either directly or indirectly
What is the main cause of tapeworm infection in humans?
Eating undercooked or raw meat from animals with tapeworm
What are the three most common tapeworms? Which animals do they come from?
Taenia saginata (beef), Taenia solium (pork), diphyllobothrium latum (fish)
How do cows/pigs become infected with tapeworm?
Ingesting food that has been grown in areas that are contaminated with Taenia eggs from human feces
Once in the cow/pig where do taenia eggs go?
The eggs hatch in the intestine and go to the muscle where they become cysticerci
When do humans become infected with taenia?
Ingestion of raw/undercooked meat that contains infective cysticerci
Where do taenia go once in the human?
Travel to intestine where mature into adult tapeworms and produce segments and eggs that pass in feces
How can a human get cysticercosis?
Ingestion of T. solium; or when a person who has tapeworm infects themself
What is cysticercosis?
Eggs that are ingested hatch in the intestine and then pass through the intestinal wall and go to striated muscle as well as brain, liver, and other tissue where develop cysticeri
What is neurocysticerocosis?
Cysticeri (from tapeworm) localizes to the brain; serious
What produces the largest tapeworms that can infect people?
Diphyllobothrium latum
How are cryptococcosis and cryptosporidium different?
cryptococcosis is an opportunistic mycoses resulting from environmental yeasts; yeasts are inhaled and then lead to lung infection and either pneumonia/disseminated disease and meningitis if compromised
cryptosporidium is ingested as an oocyst and leads to watery diarrhea; from ingesting contaminated water; usually if healthy cleared in 1-2 weeks
