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Flashcards in LOs: 10 Deck (24):
1

10 Parasites vs. Bacteria:

Prokaryotic/Eukaryotic

Nucleus

Ribosomes

Mitochondria

Cell wall

Sexual reproduction

P: eukaryotic
B: prokaryotic

P: yes
B: no

P: 80S
B: 70S

P: yes
B: no

P: no
B: yes (peptidoglycan)

P: yes
B: no

2

10 Types of Parasites:

Endoparasites

Protozoa

Helminths

Ectoparasites

- Live inside body of host

- Unicellular, free living
- LocomotionL flagella, cilia, pseudopods, or apical microtuble complex

- Roundworms: intestinal nematodes & tissue nematodes (filarial)
- Flatworms: tapeworms (cestadoes) & flukes (trematodes)

- Life cycle requires interaction w/ skin or hair of host
- Lice, scabies, & ticks

3

10 Parasite Life Cycle

Life cycles are different forms that parasites take as they develop & reproduce

Many require 2 or more host species

Definitive host: where parasite reaches sexual maturity

Intermediate host: asexual or larval state

4

10 Protozoa:
Entamoeba histolytica:

Life cycle

Geographic distribution

Clinical manifestations

Treatment

- Cyst is excreted by one person & ingested by another through fecally contaminated food or water
- Cyst undergoes excystation in gut & becomes a trophozoite
- New cysts are formed in gut & excreted

Worldwide, rare in US

Bloody diarrhea & liver abscess

Metronidazole

5

10 Protozoa:
Acanthamoeba

Contact lens wearers

6

10 Protozoa:
Naegleria fowleri

Brain-eating amoeba causing meningo-encephalitis

7

10 Protozoa:
Giardia lamblia:

Geographic distribution

Clinical manifestations

Higher risk

Worldwide, including US

Frothy, smelly diarrhea & abdominal bloating

IgA deficiency

8

10 Protozoa:
Cryptosporidium spp.:

Geographic distribution

Clinical manifestations

Worldwide, including US

Prolonged diarrhea

9

10 Protozoa:
Microsporidia:

Geographic distribution

Clinical manifestations

Higher risk

Worldwide, including US

Diarrhea

Immunocompromised (AIDS)

10

10 Protozoa:
Trichomonas vaginalis:

Life cycle

Geographic distribution

Clinical manifestations

Diagnosis

Treatment

Passed from asymptomatic men to women

Worldwide, including US

Tricomoniasis, Vaginitis, Cervicitis (STI): vaginal discharge, frothy, fish-like odor

Pear-shaped, flagellated organisms w/ twitching motility

Metronidazole

11

10 Protozoa:
Plasmodium spp.:

Most common/lethal species

Clinical manifestations

Falciparum

Malaria

12

10 Protozoa:
Babesia:

Clinical manifestations

Microscopic diagnosis

Life cycle

Geographic distribution

Babesiosis & anema

Maltezer cross

Tick vectors

Northeastern US

13

10 Protozoa:
Leishmania spp.:

Life cycle

Geographic distribution

Clinical manifestations

Sandlfy vectors

Central & South America, Middle East, & Africa

Cutaneous leishmaniasis
- Skin ulcers
- Most often seen in American troops infected in Iraq or Afghanistan

Visceral leishmaniasis
- Kala azar
- Fevers & hepatosplenomegaly

14

10 Protozoa:
Trypanosoma spp.:

Clinical manifestations

American trypanosomiasis
- Location: Central and South America
- Transmitted by “kissing bugs”
- Causes Chagas’ disease (esophageal and colon dysmotility, cardiomyopathy)
- Propagates through blood transfusions and through mother to child transmission

African trypanosomiasis
- Transmitted by the tsetse fly
- Causes sleeping sickness (fatal meningo-encephalitis)

15

10 Protozoa:
Toxoplasma gondii:

Clinical manifestations

Chorioretinitis (congenital)

Lymphadenopathy (acute infection)

Brain abscesses (reactivation)

16

10 Helminths:
Roundworms:
Intestinal Nematodes:

Ascaris lumbricoides

Hookworm (Necator americanus, Ancylostoma duodenale)

Pinworm (Enterobius vermicularis)

Strongyloides stercoralis

Whipworm (trichuris trichiura)

Life cycle

Geographic distribution

Clinical manifestations

Treatment

US, anemia

Cutaneous larva migrans

US, anal itch

US, hyperinfection syndrome

US, anemia

- Female worm in gut produces eggs
- Humans infected by ingestion of eggs (Ascaris, Enterobius, whipworm) or penetration of skin (hookworm & Strongyloides)

Impoverished rural areas (pinworm isn't associated w/ specific socioeconomic level in US)

- Abdominal discomfort, anemia
- Pinworm: perianal itch
- Strongyloidiasis: disseminated infection

Albendazole / mebendazole or ivermectin

17

10 Helminths:
Roundworms:
Tissue Nematodes:
Onchocerca, Wuchereria, Brugia:

Predominant feature

Life cycle

Clinical manifestations

Filiariasis transmitted by mosquitoes or other insects

- Mosquito bite passes eggs into lymphatics
- Eggs mature into worms & discharge microfilariae into blood

River blindness (onchocerciasis) & elephantiasis

18

10 Helminths:
Roundworms:
Tissue Nematodes:
Trichinella:

Life cycle

Clinical manifestations

Ingestion of raw or undercooked contaminated meats

Trichinellosis / trichinosis, myalgias, & eosinophilia

19

10 Helminths:
Flatworms:
Trematodes (flukes):
Schistosoma hepatobium, japonicum, & mansoni:

Life Cycle

Clinical Manifestations

Diagnosis

Treatment

- Cercariae are released from snail in slowly moving fresh water
- Cercariae penetrate skin of humans entering water
- Eggs migrate to lungs & liver to mature into adult worms
- Worms migrate via GI tract or bladder veins to be released in feces or urine

- Acute schistosomiasis (Katayama fever)
- Chronic schistosomiasis (liver disease, bladder cancer)

Eggs in urine or feces

Praziquantel

20

10 Helminths:
Flatworms:
Cestodes (tapeworms):
Taenia solium

Pork tapeworm

Ingest eggs or consume undercooked pork containing infectious larval cysts (cysticerci)

Neurocysteicercosis: most critical location in brain, causes seizures in Latin America & Asia

21

10 Helminths:
Flatworms:
Cestodes (tapeworms):
Taenia saginata

Beef tapeworm

Doesn't disseminate

22

10 Helminths:
Flatworms:
Cestodes (tapeworms):
Echinococcus granulosus

- Carried by dogs
- Ingest eggs after contact w/ dog or food contaminated by dog feces
- Eggs hatch in GI tract to form oncospheres that penetrate intestinal mucosa & enter circulation
- Oncospheres encyst in human organs

Cause Hydatid disease & liver cysts

23

10 Antimalarial Treatment:

Chloroquine

Quinine

Primaquine

Artemisinin derivatives

Mefloquine (Lariam)

Atovaquone/proguanil (Malarone)

For erythrocytic stages of Plasmodium spp. (eliminated in most parts of world due to resistance)

For erythrocytic stages of Plasmodium spp.

For exoerythrocytic, hypnozoite forms of P. vivax & P. ovale in liver

For chloroquine-resistant & quinine-resistant strains (used as combination therapy)

For chloroquine-resistant malaria

For chloroquine-resistant malaria

24

10 Antiparasitic Treatment:

Trichomonas, Giardia, Amebiasis

Pinworm, whipworm, Ascaris, Echinococcus,
Strongyloides, cysticercosis

Strongyloides, Ascaris, Onchocerca, whipworm,
lice, scabies

Pinworm

Lice

Lice, scabies

Metronidazole

Albendazole, Mebendazole

Ivermectin

Pyrantel

Malathion

Permethrin