LOs: 10 Flashcards
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
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
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
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
10 Protozoa:
Acanthamoeba
Contact lens wearers
10 Protozoa:
Naegleria fowleri
Brain-eating amoeba causing meningo-encephalitis
10 Protozoa:
Giardia lamblia:
Geographic distribution
Clinical manifestations
Higher risk
Worldwide, including US
Frothy, smelly diarrhea & abdominal bloating
IgA deficiency
10 Protozoa:
Cryptosporidium spp.:
Geographic distribution
Clinical manifestations
Worldwide, including US
Prolonged diarrhea
10 Protozoa:
Microsporidia:
Geographic distribution
Clinical manifestations
Higher risk
Worldwide, including US
Diarrhea
Immunocompromised (AIDS)
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
10 Protozoa:
Plasmodium spp.:
Most common/lethal species
Clinical manifestations
Falciparum
Malaria
10 Protozoa:
Babesia:
Clinical manifestations
Microscopic diagnosis
Life cycle
Geographic distribution
Babesiosis & anema
Maltezer cross
Tick vectors
Northeastern US
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
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)
10 Protozoa:
Toxoplasma gondii:
Clinical manifestations
Chorioretinitis (congenital)
Lymphadenopathy (acute infection)
Brain abscesses (reactivation)
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
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
10 Helminths:
Roundworms:
Tissue Nematodes:
Trichinella:
Life cycle
Clinical manifestations
Ingestion of raw or undercooked contaminated meats
Trichinellosis / trichinosis, myalgias, & eosinophilia
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
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
10 Helminths:
Flatworms:
Cestodes (tapeworms):
Taenia saginata
Beef tapeworm
Doesn’t disseminate
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
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
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
