Killer Protists

By: Dillon Petersen


Plasmodium is a large genus of parasitic protozoa. Infection with these protozoans is known as malaria. The parasite always has two hosts in its life cycle: a mosquito vector and a vertebrate host. The genus contains about 200 species in divided into several subgenera. At least ten species infect humans; other species infect other animals, including birds, reptiles and rodents.


The genus Trypanosoma contains a large number of parasitic species which infect wild and domesticated animals and humans in Africa. Commonly known as African sleeping sickness, human trypanosomiasis is caused by the species Trypanosoma brucei and is transmitted to humans through either a vector or the blood of ingested animals. The most common vector of Trypanosoma brucei is the tsetse fly, which may spread the parasite to humans and animals through bites. Through a process known as antigenic variation, some trypanosomes are able to evade the host's immune system by modifying their surface membrane, esentially multiplying with every surface change. As the disease progresses, Trypanosoma brucei gradually infiltrates the host's central nervous system. Symptoms include headache, weakness, and joint pain in the initial stages; anaemia, cardiovascular problems, and kidney disorders as the disease progresses; in its final stages, the disease may lead to extreme exhaustion and fatigue during the day, insomnia at night, coma, and ultimately death. Human trypanosomiasis affects as many as 66 million people in sub-Saharan Africa.


Giardia is a microscopic parasite that causes the diarrheal illness known as giardiasis. Giardia is found on surfaces or in soil, food, or water that has been contaminated with feces from infected humans or animals.

Giardia is protected by an outer shell that allows it to survive outside the body for long periods of time and makes it tolerant to chlorine disinfection. While the parasite can be spread in different ways, water (drinking water and recreational water) is the most common method of transmission.

Giardia infections usually clear up within a few weeks. But you may have intestinal problems long after the parasites are gone. Several drugs are generally effective against giardia parasites, but not everyone responds to them. Prevention is your best defense.


The dinoflagellates are a large group of flagellate protists that constitute the phylum Dinoflagellata. Most are marineplankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth. Many dinoflagellates are known to bephotosynthetic, but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey, (phagotrophy).[1] In terms of number of species, dinoflagellates form one of the largest groups of marine eukaryotes, although this group is substantially smaller than the diatoms.

Dinoflagellates are protists which have been classified using both the International Code of Botanical Nomenclature and the International Code of Zoological Nomenclature, approximately half living dinoflagellate species are autotrophs possessing chloroplasts and half are non-photosynthesising heterotrophs. It is now widely accepted that the ICBN should be used for their classification. Dinoflagellates and their cysts belong to the Division Pyrrhophyta, Class Dinophycaea, the related Class Ebriophyceae includes the ebridians which have internal siliceous skeletons, are extant and have a fossil record beginning in the Palaeocene.