5 The protozoa Flashcards
Protozoa are eukaryotes ranging in size 2nm to 100nm. Protozoa is a loose term used for free living organisms which feed on organic matter
Where to protozoa exist in the human body
Intracellular parasites - e.g RBC, macrophages, epithelial cell,s brain, muscle. Obtain nutrients by direct uptake or ingestion of cytoplasm
Extracellular - e.g blood, intestine, genitourinary. Obtain nutrients directly or by ingestion of host cells.
How to protozoa normally replicate
Usually asexual by binary fission, or multiple division of growing stages called trophozoites. Asexual reproduction gives potential for rapid increase in number, particularly when host defence impaired. e.g toxoplasma most pathogenic in foetus/ neonates
Sexual reproduction usually absent, or occurs in insect vector
Cryptosporidium is exceptional as undergoes asexual and sexual reproduction in humans.
Examples of protozoa which infect intestinal tract
Transmission via ingestion of cysts in food or water
Entamoeba histolytica - amoebiasis
Giardia intestinalis - giardiasis
Cryptosporidium spp - cryptosporidioisis
Cystoisospora belli - cystoisosporiasis
Cyclospora cayetanensis - cyclosporiasis
Microsporidia - microsporidiosis
Which protozoa infects urogenital tract
How is it transmitted
Trichomonas vaginalisis - trichomoniasis
Sexual
What are examples of protozoa which infect blood and tissue
Trypanosoma spp. - trpanosomiasis
Leishmania spp - leishmaniasis
Plasmodium - malaria
Toxoplasma gondii - toxoplasmosi
What are species of trypanosoma
How is trypanosomiasis transmitted
T Cruzi - Chagas disease. Reduviid bug. Also vertical transmission
T. brucei gambiense. Tsete fly
T. brucei rhodesiense. Tsetse fly
What are species of leishmaniasis
How is it transmitted
Cutaneous -
L tropica
L major
L mexicana
Mucucutaneous -
L braziliensis
Visceral (kala-azar) -
L donovania
L infantum
Sandlfy
What are plasmodium species
How is it transmitted
P falciparum P vivax P ovale P malariae P knowlesi
Anopheles mosquito
How is toxoplasma transmitted
Ingestion of cysts in raw meat
Ingestion of oocysts from cat faeces, via environmental contamination
Vertical transmission
What are some examples of strategies protozoa use to avoid host responses
Trypanosomes udnergo antigen variation of surface antigens, so evade recognition
Malaria parasites show polymorphisms in dominant surface antigens
Amoebae can consume complement at cell surface
Patient with liver abscess. What anti-microbials should they be on/ which organisms should be covered?
Bacterial - streptococci anginosus/ milleri, enterobacter
Parasitic - entamoeba histolytica (protozoa).
Co-amox/gent covers bacterial causes, and metronidazole covers amoebic liver abscess
If amoebic cysts in stool, will need further treatment with diloxonate or paramomycin
Visits Guyana, returns with papule which enlarges over time. rolled up edges. What is most likely cause?
Myiasis
Infected insect bite
Cutaneous leishmaniasis
Pyoderma gangrenosum
Cutaneous Leishmaniasis based on travel history and lesion
Biopsy lesion for microscopy, culture and molecular testing
