Chapter 1

PARASITISM


 

            In its broad, ecological sense, “parasite” means an organism that feeds on the living tissues of another organism (called host) and causes harm to it without eating it entirely. An organism eating whole bodies of other organisms is called a predator, while an organism feeding on the tissues of another without causing harm to it is called a commensal.

            In a narrower, medical sense, the term “parasite” is restricted to “animal” parasites, i.e. those belonging either to the motile unicellular eukaryotes unofficially called “protozoans” or to the multicellular animals (metazoans). For that reason, our parasitology course will not include viral, bacterial or fungal pathogens. Instead, because it aims at giving an idea about the diversity and evolution of animals, it will occasionally include metazoans that are not parasites. Some of them are interesting for the medical student as venomous animals, while others have no medical importance.

            To understand the relationships between different parasites, the student needs to have a basic knowledge of taxonomy. A quick indicator: if you have no idea who Linnaeus was, you are poorly prepared for our course and should make an effort to fill the gaps in your background. Below are the major taxonomic ranks, from higher to lower level:

 

Kingdom

            Phylum

                        Class

                                    Order

                                                Family

                                                            Genus

                                                                        Species

 

            By convention, to each taxon is assigned a Latin name, although many have also names in English and other languages. For example, the scientific name of human as species is Homo sapiens; it belongs to genus Homo, family Hominidae, order Primates, class Mammalia, phylum Chordata, kingdom Animalia (Metazoa). Warning: we insist on the Latin names!

            Our course will move from simpler to more complex organisms, so naturally we are beginning with unicellular (protozoan) parasites.

 

 

 

Main references


            Barrett M.P., R.J. Burchmore, A. Stich, J.O. Lazzari, A.C. Frasch, J.J. Cazzulo, S. Krishna (2003). The trypanosomiases. Lancet 362: 1469-1480.

            de Souza W., T.M. de Carvalho, E.S. Barrias (2010). Review on Trypanosoma cruzi: Host Cell Interaction. Int. J. Cell Biol. [Online] http://www.hindawi.com/journals/ijcb/2010/295394/

            Ghaffar A. (2010). Parasitology – chapter one. Intestinal and luminal protozoa. In: Microbiology and immunology on-line. [Online] http://pathmicro.med.sc.edu/parasitology/intest-protozoa.htm

            Ghaffar A. (2009). Parasitology – chapter two. Blood and tissue protozoa. In: Microbiology and immunology on-line. [Online] http://pathmicro.med.sc.edu/parasitology/blood-proto.htm

            Rendón-Maldonado J.G., M. Espinosa-Cantellano, A. González-Robles, A. Martínez-Palomo (1998). Trichomonas vaginalis: in vitro phagocytosis of lactobacilli, vaginal epithelial cells, leukocytes, and erythrocytes. Exp Parasitol. 89(2): 241-250. [Online] http://biblioteca.cinvestav.mx/indicadores/texto_completo/cinvestav/1998/76959_2.pdf

            Sehgal D., A. Bhattacharya, S. Bhattacharya (1996). Pathogenesis of infection by Entamoeba histolytica. J. Biosci. 21: 423-432. [Online] http://www.ias.ac.in/jarch/jbiosci/21/423-432.pdf

            Simpson A.G.B., J. Lukeš, A.J. Roger (2002). The Evolutionary History of Kinetoplastids and Their Kinetoplasts. Mol. Biol. Evol. 19: 2071-2083. [Online] http://mbe.oxfordjournals.org/content/19/12/2071.full

            World Health Organization (2012). Chagas disease (American trypanosomiasis). [Online] http://www.who.int/mediacentre/factsheets/fs340/en/

            Ximenez C., P. Morán, L. Rojas, A. Valadez, A. Gómez, M. Ramiro, R. Cerritos, E. González, E. Hernández, P. Oswaldo (2011). Novelties on amoebiasis: a neglected tropical disease. J. Glob. Infect. Dis. 3: 166–174. [Online] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3125031/

 

URL http://www.mayamarkov.com/biology/P01Parasitism/P01Parasitism_eng.htm

 

Published in 2013

Copyright © Maya Markova


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