Parasitology Flashcards
What is a parasite
An organism which lives in or on another organism and benefits by deriving nutrients at the host’s expense
What is symbiosis
Living together, long term interaction between the 2 species
Mutualism
an association in which both species benefit
Parasitism
association in which the parasite benefits and the host suffers some injury
Commensalism
An association in which the parasite only is benefiting without harming the host
Definitive host
Haarbours the adult stage of the parasite or where parasite sexually reproduces
Reservoir host
An species infected by a parasite which serves as a source of infection for other species
Intermediate host
Harbours the larval or asexual stages of the parasite
Paratenic host
Host where the parasite remains viable without further development
Protozoa
Single celled organisms - can be free living or parasitic in nature and multiply in humans
What are the 4 categories of phylum protozoa + examples
- Flagellates - Giardia
- Amoeboids - Entamoeba
- Sporozoans - Malaria, cytposopridia
- Trypanosomes - Trypanosoma, Leishmaniasis
What are the 3 classifications of parasite
Phylum protozoa
Helminths
Ectoparasites (anthropods)
Helminths
Large multicellular organisms - adults visible by eye - adults cannot multiply in humans
What are the 2 categories of helminths
- Platyhelminth (flatworms)
- Nematodes (round worms)
Categories and examples of flatworms
- Cestodes (tapeworms) - Taenia sp
- Trematodes (flukes) - Schistosoma sp
Categories and examples of ring worms
Intestinal nematodes - Ascaris lumbricoides
Tissue nematodes - Wuchereria bancrofti
Ectoparasites
Broadly include blood sucking anthropods and those that burrow into skin
Examples of ectoparasites
Insects - Anopheles (mosquito)
Lice - Pediculus humaus capitus
Mites - Scabies sp
Arachnids (ticks) - Argasids
What types of life cycle can a parasite have
Direct
Simple indirect
Complex indirect
Ascariasis - Parasite + transmission
Macroparasite - INTESTINAL NEMATODE - Ascaris lumbricoides
- Acquired by ingestion of eggs
Ascariasis Life cycle
- Formed in human intestine and secreted in faces
- Egg is fertilized in nature and reingested in food
Ascariasis clinical features
Lung migration = Loefflers syndrome - haemoptysis, dry cough
Intestinal phase - Malnutrition, malabsorption, Intestinal obstruction (worms)
Ascariasis treatment
- Albendazole prevents glucose absorption by worm so it starves
Schistosomiasis sp.
Macroparasite - Helminth - PLATYHELMINTH - fluke - Schistosoma
Life cycle of schistosoma
- Eggs that hatch infect snails
- Snails are the intermediate host and infect humans by penetrating skin
- Schistosomulae is formed which develops
Schistosomiasis clinical
- Katayama syndrome
- Chronic schistosomiasis
- Bladder fibrosis and dysfunction (Urinary)
- Liver cirrhosis, Abdo pain, Portal hypertension
Schistosomiasis- Treatment
- Praziquantel - increased ionic permeability, tetanic contraction, detachment, death.
Hydatid disease
Macroparasite - PLATYHELMINTH - Tapeworm - Echinococcus sp.
Hydatid disease- Life cycle
- Formed in small intestine and embryonic egg secreted in faeces.
- Hyatid cyst in organs
- Scolex attatches to intestine
- Usual host is sheep, dog - human can be accidental
Hydatid disease- Clinical
- Cysts 70% liver, 20% lungs
- Mass effect
- Secondary bacterial infection
- Potential cyst rupture
Hydatid disease treatment
- Albendazole + praziqantel for daughter cysts
Malaria
Microparasite - Protozoa - sprozan - caused by specied of PLASMODIUM
Strongyloidiasis life cycle
- Rhabditiform larvae in intestine are excreted
- Develop into infective filariform
- Penetrate skin and migrate to small intestine
- Adult worm in intestine deposits eggs
Strongyloidiasis clinical
- Strongyloidiasis hyper infection syndrome mortality 90%
Strongyloidiasis parasite
Strongyloides - roundworm
Strongyloides Treatment
- Ivermectin
- Albendazole
- Stop or reduce immunosuppressive therapy
Malaria life cycle - mosquito
- Mosquito take blood whilst injecting sporozoites
- Sporozoites infect liver cell
- Erythrocytic cycle forms gametocytes
- Gametocytes ingested by mosquito
Malaria- Clinical
- rupture red blood cells, block capillaries
- fever and rigors
- Cerebral malaria
- Renal failure
What are the different lengths of Erythrocytic cycle
P.knowlesi = 24 hours
P.falciparum, P.vivax, P.ovale = 48 hours
P.malariae = 72 hours
Returning traveller + fever =?
Malaria! until proven otherwise
Falciparum Malaria-Treatment
Antimalarials - co-artem
IV artesunate - haemolysis may occur so Hb levels should be checked
Non-Falciparum Malaria treatment
- Oral chlorquine
- Vivax and Ovale need Primaquine 14 days to treat Liver form
Cryptosporidiosis parasite
- Caused by Cryptosporidium parvum and hominis - microparasite - SPOROZOAN - PROTOZOA
Cryptosporidiosis life cycle
- Oocyte exits host
- Contamination of food and water with oocyte
- Oocyte ingested by host
Cryptosporidiosis- clinical
- Watery diarrhoea (no blood)
- Bloating, cramps, nausea
Cryptosporidiosis- treatment
- Rehydration, Nitazoxanide
For immunocompromised: - Paromomycin, Nitazoxanide, Octreotide
Trichomoniasis parasite
Caused by Trichomonas vaginalis - FLAGELLATED protozoan
Trichomoniasis - clinical
Men - asymptomatic
Women - Smelly vaginal discharge, haemorrhages on cervix, dysuria
Trichomania life cycle
- Trophozoite in vaginal secretion
- Multiplies and infects vagina and urethra
- Transmitted by sex
Trichomoniasis treatment
- Metronidazole single dose
Giardiasis parasite
Caused by Flagellated protozoan - GIARDIA DUODENALIS
Giardiasis life cycle
- Infective cysts excreted, contaminate water and food
- Contaminated contents is ingested
Giardiasis treatment
Metronidazole/tinidazole
- No vaccine available
