PH1123 - protozoa & helminths Flashcards
What are the properties of protozoa?
Eukaryotic, unicellular, heterotrophic, lives in or on other organisms often in aqueous environments
What are the 2 stages of the malaria life cycle?
Erythrocytic cycle and the Exoerythrocytic cycle.
How can malaria be prevented?
Mosquito control- nets, insecticides.
Prophylaxis- chosen on many factors e.g risk of exposure.
What is the exoerythrocytic cycle
Stage that involves the liver, this is where the parasite multiplies in the liver cell. It then bursts releasing merozoites.
What is the erythrocytic stage?
Merozoites infect erythrocytes to form an immature then a mature trophozoite, the immature trophozoite can either form a gametocyte which will be ingested by a mosquito or can mature and causes lysis of the cell so more merozoite is released.
Why does prophylaxis have to be taken up to 4 weeks after leaving an endemic area?
Malaria prevention drugs only work in the erythrocytic cycle so if a patient stops taking treatment and a merozoite releases then symptoms will start to appear.
What are the 4 malaria prevention drugs?
Chloroquine, Mefloquine, Doxycycline, Malarone.
What are the 3 malaria treatments?
Quinine, Malarone, Riamet.
How does riamet work?
Stops the malaria parasites being able to convert haem into haemozoin this is toxic if haem gets to high so parasites in the blood stage are killed.
How does malaone work?
Interferes with pathways that make pyrimidines required for nucleic acid replication.
What does the protozoa Cryptosporidium parvum cause?
Cryptosporidiosis. If ingested causes diarrhoea, abdominal pain and nausea. its spread by the faecal oral route or by water contamination.
What is the treatment for cryptosporidiosis?
Fluid and electrolyte replacement ( no licensed drugs in the uk)
What cause amoebic-dysentery?
Entamoeba histolytica spread through contaminated water and the oral faecal route.
What are the symptoms of amoebic dysentery?
It may or may not b symptomatic and can remain latent. Ranges from mild diarrhoea to blood and mucus in the stool.
What are the two major forms of severe amoebiasis infection?
Invasion of intestinal lining causes amoebic dysentery or amoebic colitis.
If parasite reaches the blood stream then it can spread to the liver where it causes amoebic liver abscesses.
What is the life cycle of Entamoeba histolytica?
Ingestion
Cysts form and rupture
Releases amoeboid trophozoites.
feed on bacteria and reproduce asexually in the colon.
Causes ulceration and that can mean the parasite enters blood vessels.
What are the types of parasitic worms?
Flukes, tapeworms, roundworms, threadworms, hookworms, whipworms.
What infections can worms cause?
Schistosomiasis.
Lymphatic filariasis (elephantiasis)
Onchocerciasis (river blindness)
What are the symptoms of worms?
Stomach upset (pain, nausea or vomiting).
Reduced nutritional uptake.
Intestinal obstruction or bleeding.
Presence of worm in stools or vomit.
flu like symptoms (fatigue, fever)
skin rash
breathing difficulties if lungs affected.
What does mebendazole treat?
Threadworm, roundworm, whipworm by inhibiting the synthesis of microtubules.
What does praziquantel treat?
Tapeworm, whipworm, roundworm by increasing the permeability of the membranes causing paralysis.
What are the drugs that treat worms called?
Anthelmintic.
