Treatment of Protozoal and Helminthic Infections

Question 1

Name the protozoa that infect the small and large intestine

Answer 1

Small - Giardia lamblia and cryptosporidium parvum.

Large - Entamoeba histolytica

Question 2

What is the treatment for G. lamblia?

Answer 2

Single dose of metronidazole or tinidazole

Question 3

What is the treatment for cryptosporidial infections?

Answer 3

Paromomycin, nitazoxanide and spiramycin despite having limited evidence they impact the severity or duration of diarrhoea of the immunocompromised,

Question 4

Describe the treatment of amoebiaasis

Answer 4

• Intestinal infection is treated with metronidazole but chronic infection can occur if resistant to metronidazole. Then it is treated with diloxanide fuorate. Amoebic abscess require treatment with metronidazole at higher conc

Question 5

Describe features of metronidazole

Answer 5

• It generates toxic radicles that damages bacterial and protozoal DNS.
• Active against entamoeba histolytics and giardia lamblia.
• Penetrates tissue so good at amoebic liver abscess.
• Metallic taste and causes acute nauseous reaction with alcohol.

Question 6

Describe features of Diloxanide furoate

Answer 6

• Luminal amoebicide which causes side effects of flatulence, itchiness and hives but is generally well tolerated with minimal toxicity

Question 7

Describe features of paromomycin

Answer 7

• Aminoglycoside which is given orally and not absorbed from the GI tract so is used to kill amoebic cystic stage. Side effects include abdo cramps, diarrhoea, heartburn, nausea and vomiting.

Question 8

What are features of oral rehydration therapy?

Answer 8

Involves replacement of fluids and electrolytes lost during diarrhoeal illness. Most acute, watery diarrhoea can be treated with ORS

Question 9

Explain some of the prevention mechanisms for protozoal infections of the GI tract

Answer 9

• Improved hygine and water supplies,
• Eating only freshly prepared food serves hot,
• Avoiding salads and fruit which cannot be peeled,
• Avoiding tap water and ice cubes

Question 10

Name some examples of nematodes that infect blood and tissue and that infect intestines

Answer 10

B+T - Brugia and mansonella.

Intestines- Ascaris, hookworm, enterobius and trichiuris

Question 11

Name some taenia and echinococcus examples of cretodes

Answer 11

Taenia - Taenia solium.

Echinococcus - E. Granulosus

Question 12

Name some examples of vectors for different helminths

Answer 12

Flies - Onchocerciasis (river blindness),

Aedes mosquito - Filariasis,

Chrysops (deer flies) - Guinea worm,

Snails - Schistosomiasis, capillaria and fasciola

Question 13

Name some examples of helminths whos main pathogenic mechanism is inflammation

Answer 13

• Filariasis,
• Enterobis,
• Schistosomiasis,
• Toxocariasis

Question 14

Name examples of helminths whos main pathogenic mechanism is competition for nutrients

Answer 14

• Hookworm, ascaris, tapeworms and trichiuris trichiura.
• They tend to have a more severe impact on people who already have poor nutrition. It can cause slowed intellectual development (particularly with trichiuris)

Question 15

Name exaples of how helminths main pathogenic mechanism is by forming space occupying lesions

Answer 15

• Eggs in the wrong place,
• Cysticercosis causing CSF obstruction,
• Ascaris causing intestinal obstruction

Question 16

Describe the different approaches to the treatment of helminth infections due to their pathogenesis

Answer 16

1) Inflammation - Anti-inflammatory drugs.
2) Competition for nutrients - Reduce worm burden and support nutrition.
3) Space occupying lesions - Surgery for depcompression,
4) Stimulation of fibrosis - Helminth eradication and treatment of secondary effects

Question 17

Explain the treatment of cestodes

Answer 17

Praziquantel.

With cysticercosis need to continue anti-epileptic drugs and combine anti-helminthic treatment with steroids

Question 18

Describe the treatment of nematodes

Answer 18

• Albendazole is most effective.

- Levamisole and piperazine rarely used.

Question 19

What is the mechanism of praziquantel?

Answer 19

It isnt fully known but thought to increase calcium permeability of membranes depolarising them.

Question 20

Name some infections praziquantel is used to treat

Answer 20

Hydatid disease, cycticercosis, schistosomiasis, fascioliasis infection

Question 21

What are some of the side effects of praziquantel?

Answer 21

• Dizziness,
• Headache,
• Drowsiness,
• Somnolescence (sleepyness),
• Seizures (rare),
• Abdo cramps, nausea, diarrhoea,
• Urticaria, rash and pruritis

Question 22

What is albendazole and what is it used to treat?

Answer 22

It is a benzimidazole which is used in the treatment of nematode infections (trichiuriasis, filariasis, enterobius infection, ascariasis, hookworm etc) Some protozoa (Giardia) and some cestodes (hydatid disease)

Question 23

What is the mode of action of albendazole?

Answer 23

It binds to colchicine sensitive receptors or tubulin which prevents polymerisation into microtubules. It causes impaired glucose uptake and causes degenerative changes in worms.

Question 24

What are some side effects of albendazole?

Answer 24

• Concentrated in semen so can be teratofenic,
• Sore throat,
• Headaches and seizures,
• Acute liver failure,
• Aplastic anaemia and marrow supression

Question 25

Describe features of piperazine?

Answer 25

• Agonist activity against gamma butyric acid receptor.
• Used to treat ascaris and enterobius,
• Side effects include GI upset and rarely hypersensitivity and dizziness.

Question 26

Describe some features of Pyrantel

Answer 26

• Causes depolarising neuromucular blockade.
• Treat hook/round worms.
• Can cause intestinal obstruction if heavy worm load.

Question 27

Describe features of levamisole

Answer 27

• Nicotinic acetylcholine receptor antagonist,
• Ascariasis and mix ascaris hookworm infections.
• Side effects are abdominal pain, nausea and vomiting

Question 28

What are features of Diethyl carbamate

Answer 28

Inhibits arachadonic acid making parasites more susceptible to immune attack. It is associated with an increase in inflammation

Question 29

Describe features of Ivermectin

Answer 29

• Increases permeability of membrane to chloride ions which results in paralysis and death or parasite.
• Complicated by CNS depression

Question 30

Describe features of Niclosamide

Answer 30

It is uncommon but inhibits glucose uptake, oxidative phosphorylation and anaerobic metabolism. Used solely for tapeworm infections.
Causes dizziness, skin rashes, drowsiness and perianal itching.