Learn Basic Concepts of Parasitology






1. What is parasitism?

Parasitism is an inharmonious interspecific ecological interaction in which individuals of a species (the parasites) explore organs, tissues or cells of individuals of another species (the hosts) causing harm to these.



2. What is the difference between ectoparasite and endoparasite?

Ectoparasites are parasites that explore the external surface of the host (like, for example, mites that parasite the skin). Endoparasites are parasites that live within the body of the host (like the taenias).

Image Diversity: ectoparasite endoparasite



3. Concerning the number of hosts how are parasites classified?

Parasites that require only one host are called monoxenous parasites. Parasites that need more than one host for their life cycle are called heteroxenous parasites.



4. What is the criterion used to classify hosts as intermediate hosts or as definitive hosts?

The criterion used to classify hosts as intermediate hosts or as definitive hosts is the kind of reproduction of the parasite, sexual or asexual, within the host. The host within which the sexual reproduction stage of the parasite occurs is the definitive host. The host within which the asexual reproduction stage of the parasite occurs is the intermediate host.






5. What are vectors of parasites?

Vectors of a parasite are organisms able to transport the parasite during stages of its life cycle mediating the infection of other hosts. For example, the mosquito Aedes aegypti is the vector of the dengue virus; triatomine bugs are vectors of the Trypanosoma cruzi, protozoan that causes Chagas’ disease; mice are vectors of leptospira, bacteria that cause leptospirosis.

Image Diversity: vectors of disease



6. What is an etiological agent of disease?

An etiological agent of disease is the agent that causes the disease. It may be a living being, substance or environmental fact.



7. What is the difference between the concepts of epidemic disease and endemic disease?

Endemic diseases are those that often affect people of a given place, many or few individuals. Epidemic diseases are those of rapid spread and elevated number of new cases. An endemic disease can turn into an epidemic disease.