parasites Flashcards
Which plasmodium is the most pathogenic/lethal? What is the most feared complication of this pathogen?
P. falciparum is the most pathogenic plasmodium because it can cause end organ damage, the most important being cerebral ischemia. Ischemia is secondary to the attachment of parasitized RBCs to the wall of the endothelium (aka sequestration)
Which plasmodium species have a hypnozoite form? What drug treats hypnozoites?
p. vivax and p. ovale have hypnozoite forms that can lie dormant and cause relapse years later. Primaquine is effective against hypnozoites
which plasmodium species infects reticulocytes only? RBCs of any age? aging RBCs?
reticulocytes only - p. vivax and p. ovale
RBCs of any age - p. falciparum
aging RBCs - p. malariae
which plasmodium species has trophozoites on the edges of the RBC (accole form)?
p. falciparum
which plasmodium species can infect RBCs multiple times? Only once?
multiple infections - p. falciparum and p. vivax
single infections - p. ovale and p. malariae
which plasmodium species is associated with greatly enlarged infected RBCs? which species are associated with normal sized RBCs? which species are associated with oval shaped RBCs?
enlarged - p. vivax
normal sized - p. falciparum, p. malariae
oval shaped RBCs - p. ovale
which plasmodium species needs the Duffy blood group antigen to invade the RBC?
p. vivax
What is the life cycle of plasmodium in humans?
anopheles mosquito inject sporozoites into the blood stream -> sporozoites invade liver cells -> schizogony and formation of schizont -> rupture of liver cell and release of merozoites -> infection of RBCs -> maturation to immature trophozoite (ring stage) -> maturation to mature trophozoite -> schizogony and formation of schizont -> rupture and release of merozoites -> infection of another round of RBCs
The mature trophozoite may also develop into a gametocyte which can be taken up but a mosquito
What are the symptoms of malaria?
fever and headache, chills, joint pains, vomiting, anemia, hemoglobinuria (dark urine - black water fever)
organ failure
Which plasmodium species is associated with Band forms in infected RBCs?
p. malariae
How long does schizogony last in each plasmodium species?
falciparum - 36-48 hours (only species that has a variable time)
vivax - 48 hours
ovale - 48 hours
malariae - 72 hours
How can you distinguish between the plasmodium species on direct visualization of the blood smear?
falciparum - banana shaped gametocytes, accole form, multiple trophozoites in a single RBC
ovale - reticulocytes are oval shaped, schuffner’s dots, schizonts have 6-12 merozoites
vivax - schuffner’s dots, schizonts have 12-24 merozoites
malariae - schizonts have 6-12 merozoites, band forms
What features help diagnose babesiosis on visualization of blood smear?
maltese cross in RBC and the ring form of the trophozoite
what drugs are used to treat babesiosis?
atovoquone + azithromycin
how is babesia microti transmitted? what is its global distribution?
transmitted through the bite of the ixodes scapulars tick. Usually found in islands of the northeast US
Which nematodes have a transmission cycle that includes migration through the venous system to the lungs, up through the trachea, swallowed and settles in the small intestine?
How do these nematodes get into the venous system?
Ascaris lumbricoides - ingestion of contaminated food/soil
hookworm (necatur americanus, ancyclosomta duodenale) - penetrate though intact skin
stronglyoides stercoralis - penetrate through intact skin
What is Loeffler’s syndrome? which nematodes are associated with it?
Loeffler’s syndrome is a hypersensitivity reaction in the lung to migrating parasitic larvae. It is characterized by an accumulation of eosinophils in the lung tissue, productive cough, dyspnea, wheezing, angioedema, urticaria.
It is associated with ascaris lumbricoides, hookworm and strongyloides stercoralis
What is the primary clinical manifestation of ascaris lumbricoides?
obstruction of the intestine, biliary duct or pancreatic duct
What is the main clinical manifestation of hookworm (necatur americanus, ancyclostoma duodenale)?
microcytic anemia
What are the clinical manifestations of strongyloides stercoralis?
bowel obstruction, pneumonia, hyper infection syndrome, disseminated disease (and accompanying infection with enteric bacteria)
What are the clinical manifestations of pinworm (enterobius vermicularis)?
perianal itching when the worm migrates ectopically
What is the clinical manifestation of whipworm (trichurius trichuria)?
rectal prolapse
What are the intestinal nematodes? tissue nematodes?
intestinal - ascaris lumbricoides, strongyloides stercoralis, hookworm (necatur americanus, ancyclostoma duodenale), pinworm (enterobius vermicularis), whipworm (trichurius trichuria), trichinella spiralis
tissue - onchocera volvulus and wuchereria bancrofti
Which nematodes are treated with albendazole/mebendazole alone? Which nematodes require ivermectin? Which require pyrantel pamoate?
albendazole/mebendazole - ascaris lumbricoides, hookworm, whipworm (trichurius trichuria)
ivermectin - strongyloides stercoralis, onchocerca volvulus
pyrantel pamoate - pinworm (enterobius vermicularis)
What nematodes causes lymphatic filariasis/elephantiasis?
onchocerca volvulus or wuchereria bancrofti
What are the four species of trematodes? How are they acquired?
"Prepare to Face Closing-in Seismic Tremors" paragonimus westermani - shellfish fasciola hepatica - raw watercress clonorchis sinensis - freshwater fish schistosoma - penetration of skin
What animal is common to all life cycles of trematodes?
snails
What is unique about the eggs of trematodes?
they have a lid-like structure called the operculum
What drug is used to treat trematodes? What is the exception?
Praziquantel, except for fasciola hepatica
What are the clinical manifestations of schistosoma? What are most of these manifestations due to?
granuloma formation in the spleen and liver, portal hypertension, hematuria, bladder cancer, cercarial dermatitis (swimmer’s itch)
These symptoms are caused by an inflammatory reaction to the eggs, not the worm itself
What are the clinical manifestations of clonorchis sinensis?
bile duct cancer (cholangiocarcinoma) and gallstones
What are the clinical manifestations of paragonimus westermani?
cystic cavities in the lungs (similar to TB), hemoptysis
What type of tissue does trichinella spiralis generally infect? What are its clinical manifestations? What is the treatment for it?
infects skeletal muscle cells and cause a brisk inflammation manifesting as fever, myalgias, orbital edema, elevated CPK and eosoniphilia.
Treatment = mebendazole + steroids
What are the intestinal protozoa?
giardia lamblia, entamoeba histolytica, cryptosporidium, microsporidium
What are the free living amoeba? What is their main clinical manifestation?
naegleria fowleri, acanthamoeba, balamuthia mandrillaris cause meningoencephalitis. Acanthamoeba is associated with keratitis in contact lens wearers
What are the clinical manifestations of the only STD protozoa?
Trichomonas vaginalis causes vaginitis and cervicitis, foul-smelling, greenish discharge, itching and burning. Many people are asymptomatic
What are the clinical manifestations of giardia lamblia?
foul smelling, fatty diarrhea, weight loss, flatulence, cramps, bloating, nausea
what are the clinical manifestations of entamoeba histolytica? How would you treat an infection with e. histolytica?
Dysentery (blood, mucous and pus), liver abscess and RUQ pain, pulmonary abscess, brain abscess
metronidizole/tinidazole + iodoquinol
What are the three species of cestodes/tapeworms/flatworms?
taenia solium (and saginata)
diphyllobothrium datum
echinococcus granulosus
What is the drug of choice for the treatment of platyhelminths (tapeworms and flukes)? What are the two exceptions? What is its mechanism of action?
praziquantel
neurocysticercosis (albendazole) and fasciola hepatica (triclabendazole)
damages the worm “skin” and allows the influx of Ca2+ ions
How can you acquire the tapeworm taenia solium? What clinical manifestations would occur? How would you treat it?
Acquired from undercooked pork -> intestinal tapeworm -> praziquantel
acquired from the feces of an infected human -> cysticercosis and neurocysticercosis -> seizures, hydrocephalus, lesions in the brain -> albendezole/mebendazole b/c it has better penetration into the CSF
How do you acquire diphyllobothrium latum? How would it clinically manifest?
acquired from freshwater fish
causes a vit b12 deficiency leading to a macrocytic anemia
how do you acquire echinococcus ganulosus? How would it clinically manifest? How would you treat it?
dogs and sheep
Water Lilly sign
Vomica - salty taste in mouth when coughing
hyatid cysts in the liver
treatment = surgical excision or PAIR procedure
What are the antihelminthic drugs? How do they work?
benzimidazoles - inhibit microtubule assembly and glucose uptake by helminths
praziquantel - damage outer worm coating, allows Ca2+ influx
ivermectin - attacks nervous system of worms
pyrantel pamoate
What are the anti protozoan drugs? How do they work?
metronidazole/tinidazole - upset electron balance in parasite
nitazoxanide
TMP-SMX
What are the antimalarial drugs and when are they used?
chloroquine - only for p. oval and p. malariae and some p. vivax b/c p. falciparum is resistant
quinidine + doxycycline/clindamycin - severe infection
mefloquine - chloroquine resistance in a less severe infection
primaquine - for liver hypnozoite phase
prophylaxis - atovoquone-proguanil, doxycycline, mefloquine
What drug do you treat wuchereria bancrofti with?
diethylcarbamizine
what parasite causes microcytic anemia? what parasite causes macrocytic anemia?
microcytic - hookworm
macrocyctic - diphyllobothrium latum
which schistosome has a tropism for the liver? for the genitourinary tract?
liver - s. mansoni
GU tract - s. hematobium
The cysts for which amoeba stain positive for acid-fast stain?
cryptosporidium and the other intestinal spore-forming protozoa (isospora, microsporidium, cyclospora)
What drug is used to treat cryptosporidium?
nitazoxanide
need to restore immune system with ARV
What drug do you use to treat leishmaniasis?
amphotericin B, pentavalent antimonials (sodium stibogluconate) or miltefosine
What are the symptoms of acute chagas’ disease? chronic chagas’ disease?
acute - unilateral periorbial edema (romana’s sign), chagoma (hardened red area at the site of parasite entry)
chronic - megasyndromes: megacolon, megaesophagus, cardiomegaly
What are the clinical manifestations of cutaneous leishmaniasis? mucocutaneous leishmaniasis? visceral leishmaniasis?
cutaneous - painLESS ulcer that heals in a month and leaves a depigmented scar
mucocutaneous - ulcers in the mouth and nose that cause erosion
visceral - massive hepatosplenomegaly, grayish skin, fever, severe anemia
What type of diarrhea is caused by entamoeba histolytica? giardia lamblia? cryptosporidium/cyclosporidium?
entamoeba - bloody, mucous, pus
giardia - fatty
cryptosporidium/cyclosporidium - watery
How do you treat entamoeba histolytica?
metronidazole/tinidazole + iodoquinol (to kill dormant cysts)
What is the class of drugs used to treat nematodes (round worms)? What is its mechanism of action? What are the exceptions?
Benzimidazoles: albendazole, mebendazole, thiabendazole
mech: inhibit assembly of microtubules and inhibits glucose uptake by the worm
diethylcarbamizine is used for wuchereria bancrofti (lymphatic filariasis)
ivermectin is used for river blindness and strongyloides and is neurotoxic to the worm nervous system
