Anti-Parasitic Drugs (Buxton)

Question 1

Plasmodium sp., Giardia lamblia, Entamoeba histolytica, and Toxoplasma gondii are all examples of what kind of organism?

Answer 1

Protozoa

Question 2

Schistosoma sp. is an example of what kind of organism?

Answer 2

Trematode

Question 3

Teania sp. is an example of what kind of organism?

Answer 3

Cestode

Question 4

Ascaris lumbricoides, hookworms, Trichinella sp., and filarial worms are all examples of what kind of organisms?

Answer 4

Nematodes

Question 5

A 25-year-old medical student presents with high fever and chills, severe headache, malaise and myalgia 4 days after returning from a medical mission trip to Nigeria. He took chloroquine prophylactically to prevent malaria. His blood smear is shown in the photo. What does his blood smear show and how should he be treated?

Answer 5

P. falciparum (banana-shaped gametocyte)

Artemisinin

Question 6

What happens when plasmodium break down heme?

Answer 6

Plasmodia utilize amino acids from hemoglobin; leaving behind heme, which becomes very toxic when it accumulates in the cell.

Question 7

What treatments for malaria are inhibitors of the parasite electron transport system?

Answer 7

Atovaquone

Primaquine

Question 8

What treatments of malaria are inhibitors of heme metabolism?

Answer 8

Chloroquine

Quinine

Qunidine

Mefloquine

Artemisin

Question 9

What do inhibitors of heme metabolism do?

Answer 9

Result in build-up of toxic heme metabolites which are lethal to the parasite

Question 10

What treatments of malaria inhibit translation?

Answer 10

Tetracycline

Doxycycline

Clindamycin

Question 11

What do inhibitors of translation for the treatment of malaria do?

Answer 11

Bind to 30S or 50S ribosomal subunit to prevent parasite protein synthesis

Question 12

What treatments of malaria inhibit folate metabolism?

Answer 12

Sulfdoxine + Pyrimethamine

Proguanil

Question 13

What do inhibitors of folate metabolism for the treatment of malaria do?

Answer 13

Inhibit parasite nucleotide synthesis

Question 14

Which drugs are used for the prevention of malaria?

Answer 14

Atovaquone/Proguanil

Chloroquine

Doxycycline

Mefloquine

Primaquine

Question 15

What does malaria treatment depend on?

Answer 15

Species and resistance patterns in the geographic region where the infection occurred

Question 16

What can sensitive strains of all 4 species of Plasmodium be treated with?

Answer 16

Chlorquine or Hydroxychloroquine

Question 17

What drug must be added to the treatment regimine for P. vivax and P. ovale? Why?

Answer 17

Primaquine - hypnozoites

Question 18

What can be used to treat Chloroquine-resistant P. falciparum?

Answer 18

Atovoquone-probuanil

Question 19

A 25-year-old medical student is planning a mission trip to Uganda. Among the infectious disease precautions she must consider is prophylaxis for malaria.

Which malarial parasites are found in Uganda?

Answer 19

P. falciparum (>85%); P. malariae, P. ovale, P. vivax make up the remainder

Question 20

A 25-year-old medical student is planning a mission trip to Uganda. Among the infectious disease precautions she must consider is prophylaxis for malaria.

Which drugs are available for malria prevention? What are their mechanisms of action?

Answer 20

Atovaquone-proguanil - inhibits ETC; inhibits folate metabolism

Doxycycline - inhibits translation

Mefloquine - inhibits heme metabolism

Question 21

A 33-year-old male presents with high fever and shaking chills. He had recently returned from a 2-month long mission trip to India. He had taken malaria prophylaxis (Atovaquone-proguanil) while in India, but stopped the drug the day he left to return to the US (should be taken for 1 week after leaving malarious area). A blood smear taken to look for malaria parasites is shown. He is diagnosed with Plasmodium vivax.

How should this patient be treated? Justify choice of drugs.

Answer 21

Chloroquine + Primaquine

Must keep taking drugs after return because they’re killing parasite at different stages

Question 22

What is used to treat chloroquine-resistant P. falciparum?

Answer 22

Mefloquine

Quinine + Doxycycline/Clindamycin

Atovaquone + Proguanil (aka Malarone)

Question 23

What is used to treat Chloroquine-sensitive P. falciparum and P. malariae?

Answer 23

Chloroquine

Question 24

What is used to treat P. vivax and P. ovale?

Answer 24

Chloroquine + Primaquine

Question 25

A 12 year old boy presents with a 1 week history of malaise, weakness, abdominal cramps and diarrhea. Upon questioning, the boy admits to feeling bloated and having excessive flatulence. The stool is grey or light colored and greasy or fatty in appearance (steatorrhea) and is not visibly bloody. He had recently returned from a week long camping trip, and admits to drinking from a stream in the area. Examination of the stool reveals the parasite shown in the photograph. With which parasite is he infected?

Answer 25

Giardia lamblia

Question 26

A 12 year old boy presents with a 1 week history of malaise, weakness, abdominal cramps and diarrhea. Upon questioning, the boy admits to feeling bloated and having excessive flatulence. The stool is grey or light colored and greasy or fatty in appearance (steatorrhea) and is not visibly bloody. He had recently returned from a week long camping trip, and admits to drinking from a stream in the area. Examination of the stool reveals the parasite shown in the photograph. How is this infection treated? What do these drugs do? What other parasitic infections are treated with the same agent?

Answer 26

Metronidazole Nitazoxanide Tinidazole All 3 drugs induce DNA damage and generate toxic radicals within the parasite Entamoeba histolytica, Trichomonas vaginalis

Question 27

An ultrasound preformed on a pregnant woman in her 24th week of gestation showed her fetus to have hydrocephalis and intracranial calcifications. The mother was tested and found to have IgM antibodies to Toxoplasma gondii. What is the recommended treatment for this infection? What is the mechanism of action for these drugs?

Answer 27

Spiromycin - macrolide that binds to 50S ribosomal subunit to block protein sythesis Pyrimethamine/sulfadiazine + leucovorin - 1st 2 are inhibitors of folate metabolism; leucovorin is a rescue antidote to prevent toxicity from either of the others

Question 28

A 26-year-old Peace Core volunteer in Kenya was sent home due to 4 month history of increasing upper right quadrant abdominal pain, nausea, vomiting and diarrhea. Physical exam revealed hepatosplenomegaly. The stool was positive for blood. Stool cultures were negative for bacterial pathogens; however an ova and parasite exam revealed the eggs shown in the photo. What kind of organisms are schistosomes?

Answer 28

Trematodes - blood flukes

Question 29

A 26-year-old Peace Core volunteer in Kenya was sent home due to 4 month history of increasing upper right quadrant abdominal pain, nausea, vomiting and diarrhea. Physical exam revealed hepatosplenomegaly. The stool was positive for blood. Stool cultures were negative for bacterial pathogens; however an ova and parasite exam revealed the eggs shown in the photo. How is this infection treated? What is the mechanism of action for this drug? What else can it treat?

Answer 29

Praziquantel Increases parasite membrane permeability to calcium, resulting in parasite muscle contraction and paralysis Can treat tapeworm & trematode infections, e.g. Echinoccus sp., Tania solium, Schistosoma sp.

Question 30

While on a medical mission along the Amazon River in Peru, several children in a village present with varying degrees of abdominal discomfort. Ova and parasite exam results from stool are shown in the photographs. With which parasites are they infected? What kind of parasites are these?

Answer 30

Nematodes - Ascaris, Ancyclostoma, Trichuris

Question 31

While on a medical mission along the Amazon River in Peru, several children in a village present with varying degrees of abdominal discomfort. Ova and parasite exam results from stool are shown in the photographs. What is the treatment for this infection? How do medications work?

Answer 31

Albendazole, Mebendazole, Thiabendazole These drugs act by interfering with tubulin polymerization, leading to degradation of integument; also damages parasite intestinal epithelial cells

Question 32

What, other than nematode infections, can albendazole, mebendazole, and thiabendazole be used to treat?

Answer 32

Cysticercosis & echinococcosis

Question 33

What is pyrantel pamoate used to treat? What is its mechanism of action?

Answer 33

Roundworms & hookworms Acetylcholine agonist and depolarizing neuromuscular blocking agent. It produces rigid contraction of nematode muscles.

Question 34

In the Garawan village, 60km north of Cairo, the WHO is attempting to reduce cases of lymphatic filariasis. The photos show individuals who developed symptoms of the disease at a young age and are now unable to stand or walk for long periods of time. Which organisms cause lymphatic filariasis?

Answer 34

Lymphatic filariasis - Wuchueria bancrofti & Brugia malayi Subcutaneous filariasis - Onchocerca volvulus, Loa loa

Question 35

In the Garawan village, 60km north of Cairo, the WHO is attempting to reduce cases of lymphatic filariasis. The photos show individuals who developed symptoms of the disease at a young age and are now unable to stand or walk for long periods of time. How is are these types of infection treated? What is the mechanism of action for these drugs?

Answer 35

Ivermectin - treatment of microfilariae of Onchocerca; increases cell membrane permeability for chloride ions, causing hyperpolarization of nerve or muscle cell, leading to paralysis Diethylcarbamazine - similar to Ivermectin, but also kills adult worms

Question 36

What drugs are used to treat Babesia microti?

Answer 36

Clindamycin + quinine Atovaquone + azithromycin

Question 37

What drugs are used to treat Toxoplasma gondii?

Answer 37

Spiromycin Pyrimenthamine/sulfadiazine + leucovorin

Question 38

What drugs are used to treat Giardia lamblia?

Answer 38

Metronidazole Nitazoxanide Tinidazole