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Microbes > topic 14 > Flashcards

topic 14 Flashcards

1
Q

What are two types of parasites? What are subtypes of these? examples?

A

Endoparasites

Protozoa – single-celled

Metazoa (helminths) – multicellular
Cestodes (segmented worms)
Trematodes (flatworms)
Nematodes (roundworms)

Ectoparasites

Hexapoda:  Lice
6-legged; e.g. - “Crabs”
Arachnida:  Mites & Ticks
8-legged, e.g.- “Scabies”
Numerous disease vectors
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2
Q

What are the general features of parasitic infections?

A 
Major world problems
Complex life cycles
Co-evolution with hosts
Chronic infections
Immunopathology
No effective vaccines
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3
Q

What are some examples of adaptability of parasitic infections?

A 
Drastic life stage changes
Antigenic variation
Immunosuppression
Immunological camouflage
Drug resistance
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4
Q

What are some ways in which parasites are passed from human to human?

A

Fecal-oral
Fecal cutaneous
vector borne

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5
Q

What are some ways in which parasites are passed from animals to humans

A

fecal-oral
fecal-cutaneous
vector borne
improper cooking

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6
Q

What are some general stages of the parasitic lifestyle? What are some points of intervention in that lifecycle

A

extrahuman life stages

amplification/differentiation-public health measures

Human life stages

Infection-prophylactic vaccines (malarial chemoprophylaxis)

Maturation

Replication-Drug treatment of clinical disease

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7
Q

What type of immunity combats intracellular and extracellular parasitic infections? What cytokines are involved? What are some examples?

A

Intracellular parasites controlled by Type 1 immunity

CD4+ T cells inhibit endosomal replication
CD8+ T cells target cytosolic replication
Th1 cells. Protozoa. IFN-Gamma

Extracellular parasites controlled by Type 2 immunity

Antibody initiates complement/ADCC mechanisms
Mast cells and eosinophils release toxic granules
Helminths. Th2. Ab. IgE. IL-4.

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8
Q

What are some general characteristics of protozoa?

A

Single-celled pathogens
Complex life cycles
Intracellular/Extracellular
Vector-borne/environmental

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9
Q

What are 3 types of protozoa with examples?

A

Blood and tissues

  • Plasmodium sp. (Sporozoans; malaria)
  • Babesia sp. (Sporozoans: Babesiosis)
  • Leishmania sp. (Flagellates; chronic ulcers/visceral)
  • Trypanosoma sp. (Flagellates; African & American)
  • Toxoplasma gondii (Sprorozoan; OIs)

Intestinal

  • Entamoeba histolytica (Ameba; dysentery; liver abscess)
  • Giardia lamblia (Flagellate; chronic diarrhea)
  • Cryptosporidium parvum (Sporozoan: OI/diarrhea)

Urogenital
-Trichomonas vaginalis (Flagellate; STD)

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10
Q

What is the lifecycle of plasmodium falciparum? Where do the clinical manifestations occur?

A

Sporozoites are injected from a mosquito into human blood stream during a blood meal.

Exoerythrocytic stage: They enter hepatocytes and either continue onward as merozoites into the blood or stay latent in liver as cryptozoites (only 6-12 months)

Erythrocytic stage: The merozoites are able to target all RBCs and thus this stage is more serious in P. falciparum. They infect RBCs in signet ring stage, and go through a cycle of amplification become trophozoites, shizonts, merezoites, and then infecting more cells. This cycle is short in falciparum.

Some merozoites dont enter RBCs and are taken up by a mosquito as macrogametocytes and microgametocytes.

The clinical manifestations are mainly due to the erythrocytic cycle: anemia due to loss of RBCs, and RBCs can get sticky and cause microthromboses, etc.

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11
Q

What is the lifecycle of Plasmodium vivax? How does it differ from falciparum?

A

It is similar to falciparum. Some differences:

In the liver stage, some cryptozoites will stay latent for the whole life of the host, so they must be treated as well.

The merozoites can’t target all RBCs and thus infect less. The erythrocytic cycle is also slower making the clinical manifestations a little less serious (no microagglutinization).

If a blood smear is taken, P. vivax will have schizonts and merezoites, whereas P. falciparum will only have merezoites.

P. falciparum associated with drug resistance

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12
Q

What are some challenges for developing malaria vaccines? What is one solution?

A 
Distinct life stage antigens
Antigenic variation between strains
Replicates in RBCs (no class I or II)
Th1/CTL attack infected hepatocytes only
Polyclonal gammopathy dilutes Ag-sp Ab

Use a mosquito net

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13
Q

What are characteristics of all metazoa (helminths)?

A

Multi-cellular animals
Eggs/Larvae/Adults lifestage
Type 2 immunity
Eosinophilia

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14
Q

Waht are characteristics of nematodes? What are some examples?

A 
Nonsegmented, roundworms
Acellular/collagen-rich cuticle
Separate sexes
4 larval molts
Intestinal & tissue infections

Ascaris lumbricoides (Giant roundworm)
Trichuris trichiura (Whipworm)
Enterobius vermicularis (Pinworm)
Strongyloisdes stercoralis (Small roundworm)
Ancylostoma duodenale & Necatur americanus
(Old World and New World Hookworms)

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15
Q

What is the lifecycle of Ascaris lumbricoides?

A

Eggs are ingested.

Larvae hatch in small intestine, enter bloodstream, go to liver, go to heart, reach lung capillaries, enter alveolar spaces, migrate to trachea, are swallowed

Adults mature in small intestine, cause obstruction

Eggs pass out in feces and embryonate in the soil

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16
Q

What is the lifecycle of enterobius vermicularis?

A

Eggs are ingested

larvae hatch in SI

adults mature in colon then migrate out of anus onto perineum

adults lay eggs on perineum–>itching–>scratching–>eggs on fingers–>eggs in mouths

17
Q

What is the lifecycle of trichinella spiralis?

A

Larvae are ingested in raw or uncooked meats

Larvae live and mature in SI

Female sheds newborn larvae that enter lymph and blood (CNS damage, heart failure)

newborn larvae are carried through bloodstream and enter skeletal muscle

larva matures in muscle and nurse cell/larva complex formed.

Causes cysts. discoloration of fingernails

18
Q

What is the lifecycle of wuchereria bancrofti?

A

mosquito takes a blood meal, larvae deposited on skin then enter bite wound.

larvae enter lymph, mature in lymph (can lead to elephantiasis)

microfiliariae enter bloodstream

mosquito takes a blood meal, get larvae, infecting larvae develop in mosquito

19
Q

What is the lifecycle of onchocerca volvolus?

A

Blackfly takes blood meal, larvae crawl into wound.

adult worms mature in subcutaneous tissue

Adults shed microfilariae into subcut. tissue

microfil. migrate through subcutaneous tissue (can damage eye)

Blackfly takes blood meal, ingests larvae, infecting larvae mature in black fly

20
Q

What are some examples of tissue nematodes?

A 
Trichinella spiralis (Trichinosis)
Dracunculus medinensis (Guinea fire worm)
Toxocara canis (Dog worm/Visceral Larva Migrans)
Wuchereria bancrofti (Filarial worm/Elephantiasis)
Brugia malayi (Filarial worm/Elephantiasis)
Onchocerca volvulus (Filarial worm/River blindness)
Loa loa (Filarial worm or African eye worm)
21
Q

What are some characteristics of trematodes and what are some examples?

A 
Nonsegmented flatworms (flukes)
Adults have 2 suckers
Snails/shellfish are intermediate hosts
Miracidia infectious stage for shellfish
Cercaria infectious stage for mammals

Schistosoma mansoni/japonicum (Blood/liver fluke)

Schistosoma haematobium (Blood/bladderfluke)

Clonorchis sinensis (Oriental liver fluke)

Paragonimus westermani (Lung fluke)

22
Q

What is the lifecycle of Schistosoma Mansoni?

A

snails release cercariae, cercariae enter skin, migrate (basically burrow through tissue) to lungs, then liver via blood stream.

Adults mate in liver, then migrate to mesenterics, adults live in mesenteric venules

Eggs enter SI, are released in feces into fresh water, eggs hatch in fresh water, snails take up miracidium

Liver disease, hepatomegaly

23
Q

What are characteristics of cestodes (tapeworms)/ What are some examples?

A 
Segmented flatworms
Scolex = head
Proglottids = body segments
Proglottid = infectious unit
Humans = definitive hosts
Animals = intermediate hosts

Taenia saginata (Beef Tapeworm)

Taenia solium (Pork Tapeworm)

Diphyllobothrium latum (Fish tapeworm)

Echinococcus granulosus (Dog tapeworm)

24
Q

What is the lifecycle of taenia saginata (cow)/solium (pig)?

A

Humans ingest raw or undercooked beef containing cysticerci

Cysticerci are released from muscle into stomach

Worms mature and live in small intestine (scolex contains four suckers so it stays in SI)

Adults grow up to 10 m in length, proglottids pass in feces

Cows take up embryonated eggs——->cysticerci

25
Q

What is Cysticercosis (taenia solium)?

A

Humans take up embryonated eggs, oncospheres hatch in small intestine, enter bloodstream, penetrate tissue (cysticerci in muscle, brain, eye causes issues).

Microbes (21 decks)

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