Other Pathogenic Protozoa Flashcards
Transmission of Toxoplasma gondii
eating raw meat
cat feces
Describe the T. gondii life cycle.
- sexual development only in cat
- cysts develop in other mammals
- can get infected from oocysts shed by cats or by eating raw meat containing tissue cysts
Who does severe toxoplasmosis typically happen to?
HIV/AIDS patients, organ transplant patients, chemotherapy patients
Congenital toxoplasmosis
fetus becomes infected via placenta in women who are infected for the first time
First line therapy for toxoplasma gondii?
pyrimethamine + sulfadiazine
Parasitic infections associated with HIV in the US?
Pneumocystis jirovecii (pneumonia) Toxoplasma gondii (encephalitis) Cryptosporidium (cryptosporidiosis)
Parasitic infections associated with HIV globally?
Malaria
Leishmania
Trypanosoma cruzi (Chagas disease)
First line agent for the treatment of West African trypanosomiasis?
Pentamidine
Alternative treatment for visceral leishmania and pneumocystosis?
Pentamidine
Describe the toxicity of pentamidine.
highly toxic
50% of patients show side effects
can cause hypo or hyperglycemia (rare)
Anaerobic protozoa
Entamoeba histolytica (amebiasis) Giardia lamblia (giardiasis) Trichomonas vaginalis
Describe symptoms of an Entamoeba histolytica infection
causes diarrhea and ulcers on the lining of the intestine
What promotes the spread of amebiasis?
poor sanitation and fecal contamination of food and water
Where does amebiasis initially infect?
initially infects the intestine (sometimes reaches other organs such as liver)
Symptoms of amebiasis?
diarrhea, increased flatulence, abdominal cramps (some people develop liver abscesses)
Treatment of choice for Giardia lamblia?
Metronidazole
Nitazoxanide
Most frequent cause of recreational water-related disease outbreaks?
Cryptosporidium
Most common symptoms of Cryptosporidium
Watery diarrhea (most common) stomach cramps/pain dehydration nausea/vomiting fever weight loss
Drug of choice for cryptosporidium?
Nitazoxanide
Symptoms of Trichomonas in men?
frequently asymptomatic
Symptoms of Trichomonas in women?
vaginitis with a purulent discharge
vulvar and cervical lesions, abdominal pain, dysuria, and dyspareunia
Drug of choice for extraintestinal Entamoeba histolytica, giardiasis, and trichomoniasis
Metronidazole
What does metronidazole kill?
kills trophozoites but not cysts
Similar drug to metronidazole with less toxicity
Tinidazole
What is metronidazole treatment usually followed by?
luminal drug to eliminate asymptomatic infection
What happens with metronidazole and alcohol?
Antabuse (disulfrim) effect: nausea, vomiting, and increased heart rate
What does metronidazole inhibit?
acetaldehyde dehydrogenase
Drugs for intestinal forms of amebiasis?
Paromomycin
Iodoquinol
What is paromomycin also active against?
Cryptosporidium
What does Nitazoxanide do?
inhibits the growth of sporozoites and oocysts of Cryptosporidium parvum and trophozoites of Giardia lamblia
African trypanosomes
Trypanosoma brucei gambiense (West African trypanosomiasis ~95% of cases)
Trypanosoma brucei rhodesiense (East African trypanosomiasis ~5% of cases)
American trypanosome
Trypanosoma cruzi
Kinetoplastid parasites
Leishmania
African trypanosomes
American trypanosomes
Anti-kinetoplastid drugs for Leishmaniasis
Sodium stibogluconate or Amphotericin B
Alternatives: pentamidine or Miltefosine
Anti-kinetoplastid drugs for African trypanosomiasis
Early stage - pentamidine (West) or Suramin (East)
Late stage - Melarsoprol (East and West) or Eflornithine (West)
Anti-kinetoplastid drugs for American trypanosomiasis
Nifurtimox or Benznidazole
What is miltefosine approved for use against?
visceral leishmaniasis
First oral antileishmanial drug
miltefosine
When should you avoid using miltefosine?
during pregnancy - teratogenic
Most commonly used drugs for T. cruzi
Nifurtimox and Benznidazole
Describe administration of Nifurtimox and Benznidazole
Orally available
3-4 month course of treatment
Describe toxicity of nifurtimox and benznidazole
toxicity common - hypersensitivity, GI complications
leads to premature stoppage of treatment
Unique biology of worms
multiply outside of their definitive host in contrast to other parasites
evade immune system (infections are chronic and last for the lifetime of the host)
Most common helminth infection
Ascaris
Cestodes (Tapeworms)
Diphyllobothrium latum (Broad fish tapeworm) Echinococcus granulosus (Dog tapeworm) Taenia saginata (Beef tapeworm) Taenia solium (Pork tapeworm)
Trematodes (Flukes)
Schistosoma mansoni (Blood fluke) Schistosoma haematobium (Blood fluke) Schistosoma japonicum (Blood fluke)
Nematodes (Roundworms) - Intestinal infections
Ancylostoma duodenale Necator americanus Ascaris lumbricoides (Giant roundworm) Enterobium vermicularis (Pinworm) Strongyloides stercoralis (threadworm) Tricuris trichiura (whipworm)
Nematodes (Roundworms) - Tissue infections
Toxocara canis (Dog worm)
Cysticercosis
caused by autoinfection by ingesting eggs produced by T. solium
Describe the cysticercosis life cycle.
After ingestion, oncospheres hatch in the intestine, invade the intestinal wall, and migrate to striated muscles, develop into cysticerci, can cause serious disease in the brain
Cysticercosis infection in the brain
neurocysticercosis
Enterobiasis
pinworm disease
Trichuriasis
whipworm disease
Ascariasis
roundworm disease
Strongyloidiasis
threadworm disease
Onchocerciasis
river blindness
Visceral larva migrans caused by?
Toxocara canis
Drug therapy for helminths with broad spectrum activity
Benzimidazoles
Three Benzimidazoles currently on the market
Mebendazole
Thiabendazole (limited by toxicity)
Albendazole (useful against GI and tissue)
Mechanism of action for Benzimidazoles
binds to tubulin
inhibits formation of microtubules (cap ends)
What is albendazole a drug of choice for?
cysticercosis
What is albendazole also used for besides cysticercosis?
pinworms, hookworms, ascariasis, trichuriasis, and strongyloidiasis
What is mebendazole used for?
pinworms, hookworms, ascariasis and trichuriasis
What is praziquantel high effective against?
cestodes and trematodes
Praziquantel’s MOA?
at lower concentrations, increased muscular activity (worms detach from blood vessel walls, migrate to liver)
at higher concentrations, tegumental damage and exposes a number of tegumental antigens
may also disrupt calcium homeostasis
Therapeutic uses of praziquantel?
drug of choice for all forms of schistosomiasis
dramatically reduces egg burden in those not cured in two or three doses
used in mass treatment programs
Toxicity of praziquantel?
mild and transient adverse effects are common
more severe reaction to dying worms (immune reaction)
Ivermectin is a drug for?
drug of choice for strongyloidiasis and onchocerciasis
Structure of Ivermectin?
semisynthetic macrocyclic lactone
Ivermectin MOA?
paralyzes microfilariae
binds to glutamate-activated CL- channels found in nematode nerve or muscle cells
causes hyperpolarization by increasing intracellular chloride concentration
What does Ivermectin not kill?
does not kill adult worms
blocks release of progeny
Main therapeutic use of Ivermectin?
primarily used to treat onchocerciasis (single dose)
Other uses of Ivermectin?
Ascariasis
Enterobiasis
Strongyloidiasis
Filariasis
What is Pyrantel pamoate?
broad-spectrum antihelminth
What is pyrantel paomoate effective against?
High effective for pinworms and ascaris
Moderately effective against hookworms
active against adult and immature worms
Pyrantel paomoate MOA
depolarizing neuromuscular blocking agent
causes release of acetylcholine and inhibition of cholinesterase
worms are paralyzed and expelled
Clinical uses of Pyrantel paomoate
Ascariasis - one dose is 85%-100% effective
Pinworms - two doses two weeks apart - 95% cure rate
Scabies are caused by?
human itch mite, Sarcoptes scabiei
Treatment of scabies?
Permethrin cream (may need to pretreat with 6% salicyclic acid if crusted scabies)
Treatment of head lice?
~1% permethrin or pyrethrins
chronic infestations - 0.5% malathion
