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Foundations 3 > Parasitic Infections I - Protozoa > Flashcards

Parasitic Infections I - Protozoa Flashcards

(37 cards)

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1
Q

symbiosis

A

when two species live together

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2
Q

mutualism

A

symbiosis that brings benefit to both species

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3
Q

commensalism

A

symbiosis where one species receives all the benefit, while the othe ris neithe rbenefited nor harmed

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4
Q

parasitism

A

when one species lives at the expense of the other and often inflicts injury or damage on the other

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5
Q

Name the five types of infectious agents from most to least numerous on Earth.

A

bacteria

viruses

fungi

parasites

prions

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6
Q

general fatures of parasites

A

majority are free-living, ecologically significant, do not infect humans

minority are obligate parasites, dependent on hosts for survival

complex life cycles

level of adaptation determines clinical consequence of infection

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7
Q

parasitic diseases

A

diseases of humans caused by infections with:

protozoa

helminths

arthropods

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8
Q

human parasitic diseases

A

many more worm infections in tropics than people

infrequent in temperate, sanitated, industrialized world

found in US primarily among poor, immunocompromised, sexually active

27% of US population harbor worms

becoming more important in the US as a result of immigration, travel to endemic areas, AIDS (unusual parasites)

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9
Q

host

A

organism in which parasite lives

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10
Q

definitive host

A

harbors adult (sexual) stage of the parasite

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11
Q

paratenic host

A

harbors a form of the parasite that does not undergo further development

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12
Q

reservoir

A

animal (definitive) host that enables a parasite to persist in the environment

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13
Q

vector

A

insect that transmits infectious microorganisms from one host to another

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14
Q

cestode

A

tapeworm

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15
Q

nematode

A

roundworm

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16
Q

termatode

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A

flatworm or fluke

17
Q

zoonosis

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A

disease or infection that is naturally transferable between animals and humans

18
Q

autochthonous

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A

local, type of disease transmission in which infection acquired in the area which it is diagnosed

19
Q

general principles of parasite evolution

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A

population genetics/natural selection

host range, life cycle transitions occur in specific hosts

parasite and host genetic heterogeneity

protozoa multiply in the human host

helmminths do not multiply in the human host, worm burden determines outcome

eosinophilia

20
Q

important considerations for infectious agents

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A

route of infection

disease pathophysiology

method of diagnosis

strategies for public health intervention - lif cycle (hosts)

21
Q

problems with control of parasitic disease

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A

development of resistance to chemotherapeutic agents

political and socioeconomic problems

genomic plasticity

22
Q

intestinal protozoa

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A

amoebae or rhizopods (entamoeba histolytica)

ciliates (balantidium coli)

flagellates (giardia lamblia)

sporozoans (cryptosporidium spp.)

23
Q

amebiasis

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A

amoeba (rhizopod) - most primitive of protozoa, multiplies by binary fission and moves by means of cytoplasmic organelles called psudopodia

life cycle: cyst (passed in stool) -> ingested, excysts in the small intestine -> trophozoite (colon) -> encysts (colon)

epidemeology:

  • human is only reservoir
  • cysts are infective, allows person-to-person (fecal-oral) transmission
  • transferred among family members, in day care centers
  • affects 10 percent of world population
  • risk factors include travel to endemic area and instiutionalization

disease properties:

  • 90% are asymptomatic cyst passters
  • intestional amebiases, symptomatic cyst passer, acute rectocolitis (dysentry), rare findings include toxic megacolon, ameboma, acute amebic appendicitis
  • extraintestinal amebiasis
  • diagnosis made by examination of stool for cysts or trophozoites
24
Q

giardiasis

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A

life cycle of Giardia lamblia:

cyst (passed in stool -> ingested, excysts in small intestine -> trophozoite (small intestine) -> encysts (colon) -> cyst

epidemiology:

  • cysts survive in water
  • spread by fecal-oral transmission
  • reservoirs are humans and beavers
  • isolated causes in hikers and campers who drink untreated water
  • outbreaks due to contaminated water supply, person-to-person transfer in day care center

disease properties:

  • bloating, gas, chronic diarrhea
  • epigastric pain, malabsorption
  • villous atrophy
  • diagnosis made by examination of stool for cysts or trophozoites
25
cryptosporidiosis
**sporozoan** - protozoan with two replicatory modes (sporogony and schizogony) *Cryptosporidium* spp. - obligate intracellular organism (small bowel epithelial cells) sporogenic (sexual) cycle leads to formation of occysts, which are shed into bowel luman and passed fecal-oral transmission (oocyst immediately infective), sporozoites released from ingested oocyst infect small bowel epithelial cells **disease properties**: * normal host, watery diarrhea lasting about two weeks, self-limiting * immunocompromised host, profound, watery diarrhea, weight loss, malabsorption, eventual death * _diagnosis_ made by examination of stool for oocysts, modified acid-fast stain
26
blood and tissue protozoa
amoebae flagellates sporozoans pneumocystis carinii
27
Name the four flagellates covered.
*Trypanosoma brucei* Trypanosoma cruzi * Leishmania spp.* * Trichomonas vaginalis*
28
Name the two sporozoans covered.
* Plasmodium spp.* (malaria) * Toxoplasma gondii*
29
primary amoebic meningoencephalitis
most often caused by amoeba *Naegleria fowleri*, found in fresh water, soil occurs most often during summer months in individuals who have been in contaminated water, parasite throught to enter human through nasal mucosa fulminating meningoencephalitis leading to death within one week factors involved in pathogenesis poorly understood _diagnosis_ made by examination of cerebrospinal fluid for motile amoebae
30
African Sleeping Sickness
caused by flagellate *Trypanosoma brucei*, insect vector is the tsetse fly **life cycle** - introduced to mammal during bloodmeal, bloodform trypomastigote (mammalian bloodstream) -\> antigenic variation (mammalian bloodstream) -\> taken up by tsetse during bloodmeal, epimastigote (tsetse gut) -\> metacyclic trypomastigote (tsetse salivary gland) -\> introduced to mammal **clinical manifestation** * results from high parasitemias, diffuse meningoencephalitis * East African sleeping sickness caused by *T. b. rhodesiense* (acute disease) - abrupt onset of fever, headache, occipital lymphadenopathy) * West African sleeping sickness caused by *T. b. gambiense* (subacute, chronic meningoencephalitis) - subtly personality changes -\> somnolence -\> coma -\> death * nagana caused by *T. b. brucei* - diseaes of cattle that renders much of subsaharan Africa unsuitable for raising livestock * _diagnosis_ made by identification of trypomastigoes in blood smear
31
VSG genes and antigenic variation
\>1000 distinct genes proteins are antigenically distinct must be expressed at the end of chromosomes with the transferrin receptor genes allows for VSG switching and gene conversion to stay ahead of the immune response
32
Chagas' Disease
caused by flagellate *Trypanosoma cruzi*, insect vector is the reduviid bug found throughout the Americas, about 300,000 infected in the US **Life Cycle -** insect takes bloodmeal, defecates; metacyclics in feces contaminate bite wound or mucous membrane -\> penetrates host cell, amastigote (insdie mammalian cell) -\> bloodform trypomastigote, cell ruptures (mammalian bloodstream) -\> taken up by reduvid during bloodmeal,epimastigote (reduviid midgut), metacyclic trypomastigote (reduviid hindgut) -\> insect takes blood meal **Clinical Manifestations**: * acute phase (high parasitemia) - periorbital edema (Romana's sign), fever, anorexia, hepatomegaly, lymphadenopathy, occasional death (mostly infants) * chronic phase (undetectable parasitemia) - cardiomyopathy, megaesophagus, megacolon (autoimmune disease _diagnosis_ made xenomologically or serologically additional modes of transmission, oral route (contaminated juices), glood transfusion, transplantation, vertical transmission US blood supply screened for *T. cruzi*
33
Leishmaniasis
caused by several species of the genus *Leishmania*, vector is the sandfly **visceral leishmaniasis** - *L. donovani, L. donovani chagasi* **Old World cutaneous leishmaniasis** - L. major, L. tropica, L. ethiopia **New World cutaneous leishmaniasis** - *L. mexicana and L. braziliensis* **New WOrld mucocutaneous leishmaniasis** - *L. braziliensis* **Life Cycle** - intracellular amastigote (host macrophage) -\> extracellular promastigote (sandfly vector) -\> intracellular amastigote **Epidemiology** * visceral disease in Africa, India, Brazil * cutaneous disease throughout Latin America, Middle East * mucocutaneous disease in Latin America, Middle East * mucocutaneous disease in Latin America **Disease Syndromes** * visceral (kala azar) - parasites in macrophages of reticuloendothelial sysstem * cutaneous (oriental sore) - chronic, non-healing ulcer with heaped-up margins * mucocutaneous (espundia) - occurs months to years after cutaneous infection with *L. braziliensis*, mutilating disease of cartilage _Diagnosis_ made by detection of trophozoites in vaginal discharge or urethral exudate (men)
34
trichomoniasis
caused by flagellate *Trichomonas vaginalis* trophozoite stage only venereal transmission disease properties include vaginitis, prostatitis, urethritis _diagnosis_ made by detection of trophozoites in vaginal discharge or urethral exudate (men)
35
Malaria
caused by several species of the genus *Plasmodium*, vector is the mosquito **Life Cycle** - circulating gametocytes taken up by mosquito during bloodmeal, sporogony (sexual reproduction) occurs, sporozoites -\> mosquito takes bloodmeal, sporozoites introduced, infect hepatocytes, merozoites form -\> merozoites may remain dorman ain hepatocyte or may divide -\> cell ruptures, merozoites released -\> merozoite infects red blood cell -\> male and female gametocytes develop -\> circulating gametocytes taken up by mosquito ***erythrocytic cycle*** - trophozoit, multinucleated schizont, merozoites -\> cell ruptures, merozoites released -\> merozoite infects red blood cell -\> trophozoite **Epidemiology** * number one cause of infectious disease in the world * human is the only reservoir **Clinical Differentiation** * all species give rise to anemia, hypoglycemia, splenomegaly, splenic rupture * _diagnosis_ made by exmination of blood smear
36
toxoplasmosis
caused by obligate intracellular sporozoan *Toxoplasma gondii* **Life Cycle and Epidemiology** * both sexual and asezual cycles in cate, the definitive host * oocysts found in cat feces * livestock may ingest oocysts which break down and releases trophozoites -\> invade a variety of tissues -\> replicate to form tissue cysts * transmission to humans after ingestion of oocysts or tissue cysts -\> trophozoites -\> tissue cysts * 1 of 500 pregnant women acquires acute toxoplasmosis -\> parasite transmitted to fetus in half of these women **Disease Properties** * acute acquired disease in normal host - no symptoms or mononucleosis - like sympotoms * acute acquired or reactivation disease in immunocompromise host - encephalitis, pneumonitis, myocarditis, chorioretinitis * congenital disease - spontaneous abortion, stillbirth, severe CNS manifestations, chorioretinitis _diagnosis_ made serologically or by demonstration of trophozoites in tissue biopsies
37
pneumocystosis
caused by fungus *Pneumocystis carinii* cystic and extracystic forms cyst spherical to oval, contains up to 8 intracystic cells extracystic form is trophozoite found in lungs of many mannals, global distribution transmission probably airborne **Disease Properties** * occurs in immunocompromised patients * pneumonia _diagnosis_ made by detection of trophozoites in psutum or bronchial lavage/brush biopsies

Foundations 3 (20 decks)

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