Parasites

Question 1

how prevalent are parasitic infections? do they often cause clinical infections? and do many parasitic infections turn in disease?

Answer 1

parasitic infections are very prevalent in developed and developing countries but typically cause no clinical infections.
Very few immunocompetent individuals develop disease

Question 2

describe parasitic disease. what parasite is usually fatal?

Answer 2

parasitic disease is a consequence of prolonged, repeated, or high burden infection, usually acute or chronic, rarely fatal. 
plasmodium falciparum (malaria) - fatal in 3-5 days

Question 3

what are the 3 most common parasitic infections in order

Answer 3

toxoplasmosis, ascaries, hookworm disease

Question 4

what are many parasitic infections?

Answer 4

zoonoses - caused by animals

Question 5

do some parasites require human and nonhuman hosts?

Answer 5

yes

Question 6

when are humans dead end hosts?

Answer 6

when parasitic infection occurs in human but no parasite developmental stage - so life cycle is not completed

Question 7

what are the two types of parasites

Answer 7

protozoa and helminths

Question 8

describe protozoa biology

Answer 8

one cell eukaryotes , disease is a consequence of parasite replication to high numbers (small inoculum required to initiate infection), no free environment stage in life cycle, unable to withstand dryness.
extracellular lumen of GI tract
65 thousand species, free living most harmless, few actual parasites

Question 9

how are protozoa transmitted and describe its life cycle forms

Answer 9

protozoa- fecal oral route.

life cycle between active trophozite, dormant cyst (withstands desiccation)

Question 10

5 protozoa

Answer 10

plasmodium, giardia, cryptosporidium, leishmania, trypanosomes

Question 11

biology of mastigophora (flagellated)

Answer 11

motile by flagella, single nucleus, sexual repro by singly, division by longitudinal fission parasitic forms tend to lack mitochondria and golgi.
most form cysts and are free living, most are solitary

Question 12

examples of mastigophora

Answer 12

trypanosoma, leishmania, giardia and cryptosporidium, trichomonas

Question 13

cryptosporidum outbreak in wisconsin occurred why

Answer 13

failure of drinking water treatment

Question 14

biology of apicomplexa (sporozoa)

Answer 14

most not motile (except male gametes), complex life cycles, produce sporozoites following sexual repro, most form oocysts, entire group is parasitic

Question 15

examples of apicomplexa

Answer 15

plasmodium and toxoplasma gondii

Question 16

biology of helminths (worms)

Answer 16

multicellular (metazoa) , extracellular due to large size protected by cuticle, larvae can develop into dormant cysts
reproduce sexually
some species are hermaphroditic

Question 17

life cycle of helminths

Answer 17

complex, earth and animals reservoirs, do not typically complete cycle in humans, develop outside of humans (definitive hosts) in insects, or animals (intermediate hosts)

Question 18

describe the infection of helminths

Answer 18

most helminths cause chronic infections that are tolerated by humans, disease is not a consequence of parasitic replication.

Question 19

why are helminths described as parasitic burden?

Answer 19

due to the number of parasites that host initially acquires from environment

Question 20

how are helminth infections resolved?

Answer 20

not eliminated by host, but spontaneously resolve when adult worms reach senescence

Question 21

what are some parasitic helminths

Answer 21

tapeworms, flukes, and roundworms, can be seen by naked eye (1mm to 25 m in length)
two groups: flatworms and roundworms

Question 22

describe flatworms including phylum

Answer 22

phylum: platyhelminthes
thin, segmented
subdivisions: cestodes (tapeworms), trematodes (flukes)

Question 23

describe roundworms including phylum

Answer 23

phylum: aschelminthes
aka: nematodes
elongate, cylindrical, unsegmented

Question 24

describe parasite vectors

Answer 24

most are arthropods like tickets, flies, mosquitos

parasitic prevalence dependent on local conditions favoring vector breeding like water, foliage

Question 25

describe parasitic reservoirs

Answer 25

reservoirs - sources of parasites that do not participate directly in transmission
humans- malaria, amoebae
animals - pigs (trichinosis) and cattle (tapeworm)
environment- soil with parasitic feces

Question 26

describe the steps parasite entry

Answer 26

1. oral ingestion- contaminated food/water ascariasis, and amebiasis
2. penetration of skin: unbroken- hookworm and schistosomes
3. arthropod- borne: bite wounds, very efficient for malaria
   can be transmitted via blood transfusions