Parasites Flashcards

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1
Q

Helminths

A
  • worms

- reproduce sexually, usually within host

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2
Q

Protozoa

A
  • unicellular

- replicate quickly and asexually in host

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3
Q

Cestodes

A
  • tapeworms
  • hermaphroditic
  • segmented
  • eg. Taenia solium
  • infection by egg/larval ingestion
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4
Q

Nematodes

A
  • unsegmented
  • roundworms
  • sexes separate
  • eg. Strongyloides stercoralis, Ascaris lumbricoides
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5
Q

Trematodes

A
  • flat worms or flukes
  • unsegmented
  • hermaphroditic
  • go through intermediate hosts: snails, shellfish
  • eg. Schistosoma spp.
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6
Q

Schistosomiasis Life Cycle

A
  • eggs hatch in environment producing miracidia
  • miracidia infect snails
  • cercariae leave snails and penetrate skin of human
  • becomes schistosomulae and enters circulation, migrates to portal blood of liver
  • paired adult worms migrate to venules of rectum and bowel, lay eggs that go through liver and are excreted into environment
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7
Q

Schistosomiasis Clinical Presentation

A
  • 4 weeks post exposure presents as traveler’s diarrhea, urticaria, eosinophilia
  • chronic pathology due to egg production, lost eggs can irritate mucosa, retained eggs can become obstructive, can affect liver function (portal hypertension)
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8
Q

Schistosomiasis Distribution

A
  • mostly in Africa

- some in Asia and South Africa

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9
Q

Schistosomiasis Treatment

A
  • population based treatment is best

- treat school aged children with antihelminths

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10
Q

Strongyloides stercoralis Life Cycle

A
  • larvae excreted in stool
  • larvae develop into adults, reproduce sexually
  • larvae mature into filariform larvae that penetrate skin and initiate infection
  • filariform larvae hematogenously spread to lungs, get coughed up and swallowed into intestine
  • develop into adults, adult female produces eggs that develop into larvae
  • larvae either excreted or auto infect and restart cycle without leaving human
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11
Q

Strongyloidiasis

A

-autoinfection can lead to hyper infection, producing GI hemorrhage, pneumonitis

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12
Q

Malaria

A
  • most important parasitic disease worldwide

- majority of deaths in sub-Saharan Africa

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13
Q

Malaria Vector

A

Female anopheles mosquito

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14
Q

Malaria Parasite

A

-Plasmodium species (falciparum, vivax, knowlesi, ovale, malariae)

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15
Q

Schizogany

A

-asexual cycle in RBC’s and other tissues

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16
Q

Sporogany

A

-sexual cycle in female anopheles mosquito

17
Q

Plasmodium Life Cycle

A
  • Plasmodium in mosquito gut
  • migrate to salivary glands
  • mosquito bites human, Plasmodium transferred to human
  • Plasmodium infects liver cells, replicates there (becomes hepatic schizont, eventually ruptures)
  • Plasmodium released from liver cells into RBC’s, infects RBCS, becomes blood-stage schizont (bunch of Plasmodium in single cell)
  • Parasite picked up by a mosquito
18
Q

P. falciparum

A
  • minimal temp for devo in mosquito - 16
  • no dormant liver stage, no relapse
  • 5% cases are severe, causes majority of deaths
  • treated with Arteminsin Combo Therapy
  • common asymptomatic carriage
  • more common in Africa
19
Q

P. vivax

A
  • minimal temp for devo in mosquito - 15
  • dormant liver stage, relapse both can occur
  • asymptomatic carriage is very common
  • treatment chloroquine and primaquine
  • primaquine gets rid of hypnozoite
20
Q

Malaria stable transmission

A
  • more than 10 ix’s per year
  • most deaths occur in children
  • by adulthood, have asymptomatic parasitemia
  • sub-Saharan Africa, Asia
  • lost with immigration
21
Q

Unstable transmission

A
  • immunity does not develop
  • less than 5 ix’s per year
  • major epidemics
  • Africa and Asia
22
Q

Malaria Diagnostics

A
  • Microscopy and blood smear (thick and thin), can determine species and parasitemia
  • Rapid Antigen Test (quick results, can’t determine parasitemia, can’t pick up non-falciparium malaria, need microscopy follow up)
  • PCR
23
Q

Uncomplicated malaria

A
  • fevers, rigors, headache, myalgia
  • often mistaken as viral ix
  • tx: Atovaquone-Proguanil (attacks hepatic and blood schizonts)
  • if known it’s not falciparum - chloroquine-primaquine
24
Q

Severe malaria

A
  • coma, metabolic acidosis, pulmonary edema, hypoglycemia, renal failure
  • mortality - 10-20% w/treatment
  • tx: Artesunate + Doxycycline/Clindamycin
25
Q

Malaria and Travel

A
  • # 1 cause of fever in return traveler’s
  • 50% is falciparum
  • often due to lack of prophylaxis or improper prophylaxis regimen
26
Q

Malaria Prophylaxis

A
  • varies with travel destination, cost, side effects, activities, duration
  • mefloquine and chloroquine are weekly
  • atovaquone-proguanil and doxycycline are daily
27
Q

Taenia solium Life cycle

A
  • pigs acquire parasite from environment
  • parasite into muscle tissue
  • humans consume undercooked pig, infected with tapeworm
  • tape worm in GI tract, releases proglottids with eggs
  • human ingests eggs, can lodge in brain, eyes, skeletal muscle
28
Q

Taenia solium Epidemiology and Distribution

A
  • most common parasite of CNS
  • preventable form of epilepsy
  • found in South America, Africa and Asia