Definition
Parasites are small creatures that infest another living being in order to feed and/or reproduce. In microbiology, the term “host” is used in the context of the human or animal infested by the parasite. The host can be affected by the parasite in its life, but deaths do not usually occur.
If a person is infected by a parasite, this is called parasitosis. Parasites can also be transmitted from animals to humans. Then one speaks of a zoonosis.
Parasites can settle in or on different areas of the body. As an ectoparasite they are on the body, for example on the skin or hair, as an endoparasite they are in the body, i.e. in the intestine or bloodstream. Often a parasite infestation of humans goes unnoticed at first and the symptoms only appear after some time.
What forms of parasites are there?
There are many different types of parasites. They can be subdivided in different ways.
- Division into unicellular (protozoa) and multicellular parasites (metazoa), to which the worms belong.
- Classification according to the location of settlement into parasites living on the skin (ectoparasites) and in the body (endoparasites).
- Classification according to the duration of the infestation into stationary and temporary parasites. Stationary parasites live continuously on or in their host, like lice. Mosquitoes, on the other hand, are among the temporary parasites that only visit their host at certain times, for example to feed.
Causes of parasites
The most common cause of transmission is contaminated food or drinking water. Especially raw meat is often responsible for transmission. But a transmission of parasites from person to person is also possible, as well as from animals to humans.
The risk of parasitic transmission increases especially in places where there is close contact between humans and animals and, on top of that, poor hygiene conditions prevail. People with a poor intestinal flora are more likely to be infected if they have had contact with parasites, e.g. in the form of spoiled raw meat or contaminated drinking water. Similarly, a sugary diet offers the parasites plenty of food and promotes their settlement in the human intestine.
A strong immune system should actually prevent parasites from settling down by producing special antibodies. However, some parasites have developed survival strategies that make it impossible for the immune system to fight them. For example, they change their surface structure so that they are no longer recognized as a parasite or they secrete certain substances that suppress the immune system. This allows them to nestle undisturbed in humans and use them as hosts.
