Protozoa

what kind of oganism is protozoa

Unicellular eukaryotic organisms

can protozoa grow outside host?

Do not grow outside host

can protozoa grow in food

they are not able to grow in food but can survive in food as cyst 

protozoa vulnerability

Organism itself vulnerable to environmental stresses e.g. low pH

resistant structure protozoa

Resistant structure: cysts and oocysts

D/R protozoa

Low dose response relation

The active form of protozoa are known as

trophozoites

what does protozoa cause

Protozoa can cause foodborne infections, mainly transmitted through water 

Giardia lamblia host

man

Giardia lamblia sources 

Water fruit, man, vegetables 

 

Food sources: salads, fruits washed with contaminated water 

 

 

1. Ingested cysts in intestine. 

2. Flagellate trophozoite 

3. Multiplication in intestine 

4. Cysts 

5. Faeces 

6. Contamination of water or food

Giardia lamblia survival 

survives in food and water as cysts. This is a resistant stage that occurs when the organism forms a thick wall around itself in periods of stress. 

  

Food and water are stress situations 

 

Gastric juices help to release trophozoites

Giardia lamblia disease

giardiasis 

Giardia lamblia symptons

diarrhoea, abdominal cramps, nausea

Giardia lamblia treatment

Treatment with drugs available. 

Chlorination of water not very effective 

Entamoeba histolytica host

man

Entamoeba histolytica sources

Water ,man ( Transmission via water similar to Giardia)

Entamoeba histolytica disease

Amoebic dysentery 

Entamoeba histolytica symptons

• invading the intestinal wall  

•  spread of trophozoites from the intestine via the bloodstream  

•  amoebic liver abscess 

Entamoeba histolytica treatment

Effective drugs available

Cryptosporidium parvum host

Animal, man 

Cryptosporidium parvum sources

Water Food, man, animal 

 

Transmission oocysts through water

Cryptosporidium parvum survival 

Chlorine resistant 

(Oo)cysts resistant structure 

Cryptosporidium parvum disease

cryptosporidiosis

Cryptosporidium parvum symptons

Can be asymptomatic  

Can cause diarhhoea. Especially affecting susceptible people (“Aids defining illness”)

treatment Cryptosporidium parvum

Lesson for companies (include in HACCP plan) to make sure water is free of the pathogen 

 

Boil water 1 min to kill it  

Toxoplasma gondii host

Feline

Toxoplasma gondii sources

Meat (cat faeces) 

Cat is definitive source- full growth circle takes place inside cat 

Cat then produces oocysts that then released into environment  

Rats and mice may eat contaminated grass etc 

Toxoplasma gondii Disease  

Toxoplasmosis 

symptons 

• spontaneous abortion, eye defects, brain defects  

• changes in behaviour  

• asymptomatic 

 

Tissue cysts can be transferred from person to person via blood