Anti-helminthics and Anti-protozoals Flashcards
Describe the treatment of G. lamblia.
Intestinal trophozoite is treated with metronidazole or tinidazole (single dose)
Describe the treatment of C. Parvum.
- Drugs have been proposed for use: paromomycin, nitazoxanide and spiramycin
- BUT limited evidence that any of these drugs have an impact on the severity or duration of diarrhoea in the most immunocompromised patients
How can we distinguish between small and large intestine disease based on stools ?
infrequent large stools = small intestine (e.g. salmonella infection)
frequent small stools = large intestine (e.g. amoebic colitis)
Describe the treatment of amoebiasis.
- Intestinal infection is treated with metronidazole
- In chronic infection cysts will survive and cause relapse and are resistant to metronidazole
- Chronic infection needs treatment with diloxanide furoate
- Amoebic abscess requires treatment with metronidazole at higher and longer doses
What type of medication is metronidazole ? What is its mechanism of action ?
Originally an antiprotozoal agent.
Under anaerobic conditions it generates toic radicals that damage bacterial and protozoal DNA. Penetrates well into tissue – hence its value in amoebic liver abscess.
What pathogens is metronidazole effective against ?
Active against Entamoeba histolytica and Giardia lamblia
What are issues with the use of metronidazole ?
- A metallic taste is common and can be hard to tolerate
* Cause an acute nauseous reaction with alcohol
Diloxanide furoate
- Indication
- Type of drug
- Side effects
Diloxanide furoate
- Indication: Chronic amoebiasis infection
- Type of drug: luminal amoebicide
- Side effects: flatulence, itchiness, and hives are associated with use (but isually well tolerated with minimal toxicity)
Identify drugs on the WHO essential medicines list.
Diloxanide furoate Praziquantel Albendazole Levamisole Diethyl carbamazine
Paromomycin
- Type of drug
- Indication
- Mechanism of action
- Administration
- Side effects
Paromomycin
- Type of drug: aminoglycoside
- Indication: C parvum infection
- Mechanism of action: Kills amoebic cystic stage
- Administration: Orally (but not absorbed from GI tract)
- Side effects: abdominal cramps, diorrhoea, heartburn, nausea, and vomiting
What treatment is needed for any diarrheal illness ?
ORT
• Involves the replacement of fluids and electrolytes lost during diarrheal illness
• 90-95% of cases of acute, watery diarrhoea can be successfully treated with an oral rehydration solution (ORS)
• ORS increases the resorption of fluids and salts into the intestinal wall
Identify measures to prevent protozoal infections of the GI tract.
- Improved hygiene and water supplies
- Eating only freshly prepared food served hot
- Avoiding salads and fruit which cannot be peeled
- Avoiding tap water and ice cubes
Identify the main helminthic pathogens.
NEMATODES (ROUNDWORMS)
1) Blood and Tissue Nematodes
- Brugia
- Wucheraria
2) Intestinal Nematodes
- Ascaris
- Hookworm
- Trichiuris
CESTODES (FLATWORMS/TAPEWORMS)
1) Taenia (cause disease in humans)
- Taenia solium
2) Echinococcus (cause disease in animals)
- E. granulosus
TREMATODES (FLUKES)
1) Lung
- Paragonomiasis
2) Liver
- Opisthorcis
3) Blood
- S. mansoni
What is so special about the replication of helminths in the human body ?
If ingest one egg, get one worm, direct relation (doesn’t ever change, doesn’t really replicate in the body, except for a couple exception). If can drop amount of infection people get, may lure the worm burden into something that doesn’t cause any disease
Identify some hosts for helminths.
- Wild bore (tinea solium)
- Rats
- Humans
Identify some vectors for helminths, along with the species each carries.
- Flies: Onchocerciasis
- Aedes mosquito: Filariasis
- Crysops: Guinea worm
- Snails: Schistosomiasis, Capillaria, Fasciola
How do Schistosomiasis infections occur ?
Eggs in water, survive until find snail, then
develops. What emerges through these stages is the Cercariae which are
programmed to find something hot(i.e. a person), then burrow through skin, cause a bit of a lesion, then go into liver and mate and produce eggs (cause hepatosplenomegaly)
Identify the main pathological mechanisms of helminths.
- Inflammation
- Competition for nutrients
- Space occupying lesions
- Stimulation of fibrosis
Identify species of helminths for which inflammation is the main pathogenic mechanism.
- Filariasis
* Onchocerciasis
Describe the main features of inflammation in filarial infection.
1) Filaria do cause the disease but actually not them themselves, it’s Wolbachia bacteria living inside them that cause the disease (same as for Onchocerca helminth).
From a therapeutic POV, once kill worm, release bacteria, so worsened infection and inflammation
2) Filarial infection also associated with
acute lymphoedema, which leads to repeated cycles of inflammation and
bacterial infection, leading to Elephantiasis
Identify species of helminths for which competition for nutrients is the main pathogenic mechanism.
- Hookworms (blood)
- Ascaris
- Tapeworms
- Trichiuris trichiura
What are possible clinical consequences of infection by helminths which compete for nutrients ?
- Intellectual development may be slowed
* In general, major threat to health
True or false: consequences of infection by helminths which compete for nutrients are more severe with poor nutrition
True
What are the main clinical features of Trichiuris clinical features ?
• Vague abdominal symptoms • Trichiuris dysentery syndrome (bloody mucoid diarrhea, small frequent stools...) • Growth retardation • Intellectual compromise -micronutrient deficiency -mucosal integrity
