Protozoans

Protozoa are unicellular, eukaryotic organisms, which are already assigned to the animal kingdom. The basis for the previous classification of these organisms was their ability to move, which occurs in a variety of ways:

• amoeboid in the case of the rhizopods
• by means of cilia covering the whole cell surface in the case of the ciliates or
• by means of one or more flagella as in the flagellates.

Protozoa are characterized by several state forms:

• trophozoites: vegetative, mostly motile state form
• gamonts: initial stages of sexual development
• gametes: mature or male female gametes
• Cysts or oocysts: permanent forms with increased resistance to external agents. Mode of transmission of pathogens from one host to another.

Classification of protozoa

• Sporozoa The most important representatives are Plasmodia as the causative agent of malaria, and Toxoplasma with Toxoplasma gondi as the causative agent of toxoplasmosis and Babesia as the causative agent of babesiosis.
• Ciliates The only humapathogenic pathogen is Balantidum coli, which causes the rare balantidial dysentery with bloody mucous diarrhoea.
• Rhizopods The main representatives are the amoebae with the worldwide occurring humapathologically important species Entamoeba histolytica, the causative agent of amoebic dysentery, and Naegleria as the causative agent of meningoencephalitis.
• Flagellates (flagellates) with the humapathologically important genera: trypanosomes, leishmania, trichomonads and giardia.

1. Alberts B. et al: Molecular Biology of the Cell. Wiley-VCH, Weinheim 2003
2. Darai G et al: Encyclopedia of infectious diseases of man. Springer, Berlin 2011
3. Halliez MC et al.(2013) Extra-intestinal and long term consequences of Giardia duodenalis infections. World J Gastroenterol 19:8974-8985