Killer Protists

Plasmodium Protozoa

These cause human diseases such as malaria and many others. Malaria is caused by the protist plasmodium. The parasites are spread by a mosquito vector. Parasites enter a host’s blood through the bite of an infected mosquito. The parasites infect the host’s red blood cells, causing symptoms such as fever, joint pain, anemia, and fatigue.

Trypanosoma Protozoa

Members of the genus Trypanosoma are flagellate protozoa that cause sleeping sickness, which is common in Africa. They also cause Chagas disease, which is common in South America. The parasites are spread by insect vectors. Trypanosoma parasites enter a person’s blood when the vector bites. Then they spread to other tissues and organs. The disease could be fatal without medical treatment.

Giardia Protozoa

Giardia are flagellate protozoa that cause giardiasis. The parasites enter the body through food or water that has been contaminated by infected people or animals. The protozoa attach to the outside of your small intestine, where they prevents you from fully absorbing nutrients. They may also cause diarrhea, abdominal pain, and fever.


Diplomonads are small heterotrophic protists with no mitochondria. Some diplomonads are free-living and can be common in fresh water, but most are in the intestines of animals. Some are parasitic and cause diseases in humans. The diplomonad Giardia infects the intestine and can cause diarrhea. Although diplomonads have no hard parts and completely lack a fossil record, studies of the ribosomal RNA of diplomonads have shown that they form one of the earliest branches of eukaryote evolution.