Protozoa

Protozoa are unicellular organisms. Protozoal infections can be very dangerous to humans.

What are protozoa?

Protozoa are a group of eukaryotic organisms. In contrast to prokaryotes, eukaryotes are living things that have a nucleus. Together with the fungi and the algae, the protozoa form the group of protists. The protozoa are assigned to the animal kingdom, whereas algae are counted among the plants and fungi in turn form an independent genus.

There are many different types of protozoa. They differ in their size or in their external appearance. Protozoa are among the heterotrophic organisms. In order for their metabolism to function, they depend on substances that have been built up by other organisms.

A distinction can be made between commensal, parasitic or mutualistic interacting protozoa. Commensal interactions are profitable for one species involved. For the other species, the interaction is neutral. Parasites damage their host. Mutually interacting protozoa live in an interrelationship with the other species from which both partners can benefit. In humans, however, no mutualistic protozoa are known. Most protozoa are pathogenic, i.e. disease-causing.

According to morphological points of view, protozoa can be divided into four groups. Sporozoa (Apicomplexa) are protozoa that multiply by forming spores. The spore animals include Plasmodium, the causative agent of malaria. Cilia are ciliate animals. Their cell surface is covered with eyelashes that help them move around. The flagellates, also called flagellates, have flagella for locomotion. The leishmanias, trypanosomes and trichomonads harmful to humans belong to the flagellates. The root pods (rhizopods) form so-called pseudopods. The rhizopods include, for example, amoeba and heliozoa.

Occurrence, Distribution & Properties

The protozoa of the genus Plasmodium, more precisely the species Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale and Plasmodium vivax occur mainly in tropical and subtropical areas. Malaria pathogens are particularly widespread in Africa, in the areas south of the Sahara. Further distribution areas are Southeast Asia, South Asia and Papua New Guinea. Until the middle of the 20th century, malaria-causing plasmodia were also native to the Mediterranean region in Europe.

The plasmodia are usually transmitted to humans by mosquitoes. Suitable vectors are, for example, the mosquitoes from the genus Anopheles. The pathogen enters the human bloodstream through a bite from the infected mosquito.

The protozoon Toxoplasma gondii from the genus Toxoplasma is distributed worldwide. A large part of the population is infected with the parasite. It is transmitted to humans through the eggs of the protozoa. These oocysts are usually passed out with cat feces. Close contact with cats or cleaning the litter box are therefore possible sources of infection for toxoplasmosis. The eggs get into the earth through the excrement. Infection is therefore also possible when working in the garden or when eating vegetables that have not been adequately washed. The protozoa also enter the bodies of farm animals via the earth. The main sources of infection in humans are therefore insufficiently cooked or raw lamb and pork.

Trichomonas vaginalis, a protozoan from the Trichomonadida family, is only transmitted through direct contact. An infection with Trichomonas vaginalis is therefore one of the sexually transmitted diseases. The pathogen is distributed worldwide.

Illnesses & ailments

Various pathogens from the Plamodien family can cause malaria infection in humans. A preform of the plasmodia enters the blood through the mosquito bite and from there to the liver. The pathogens mature and divide in the liver. The resulting forms of plasmodia enter the bloodstream and attach to the red blood cells (erythrocytes). They penetrate the erythrocytes and mature into what are known as trophozoites. After multiple divisions, many merozoites develop, which cause the infected blood cells to burst. The pathogens then spread in the blood and infect other blood cells, so that the cycle starts all over again.

The typical malaria fever develops due to the breakdown of the red blood cells. It occurs every three to four days. As the fever rises, people suffer from chills. Defeverment is accompanied by sweats. In addition to the fever, impaired consciousness, seizures, and anemia can develop.

An infection with Toxoplasma gondii, toxoplasmosis, on the other hand, proceeds quietly and without symptoms in many cases. In patients with a weakened immune system, however, foci of inflammation can develop in all organs. In addition, there are changes in nature, seizures or paralysis. In these cases, toxoplasmosis can also manifest as pneumonia or meningitis.

Infection with the protozoan Toxoplasma gondii can also be dangerous during pregnancy. Toxoplasmosis during early pregnancy is a common miscarriage. Infections in the second or third trimester sometimes lead to epileptic seizures, cognitive abnormalities, intellectual disabilities, water head, chorioretinitis or calcifications of the cerebral vessels in infected children.

An infection with the parasite Trichomonas vaginalis is also known as trichomoniasis. A typical symptom of such a trichomonads infection is a foul smelling, foamy discharge. The affected women suffer from a severe burning sensation in the vaginal area. The vagina may be red or swollen. If the trichomonads have also infected the urethra, the patients can only urinate with pain. In men, too, trichomonas infection can lead to inflammation of the urethra.