Killer Protists

by Rishi Talati

What are Protists?

Protists are a very large, diverse group of organisms, including the plant-like protists (algae), fungi-like protists, and the animal-like protists (protozoans). They are all eukaryotic, most are unicellular, and they are classified under the Kindom Protista.

Killer Protist #1:

Dinoflagellate (Dinoflagellata)

The dinoflagellates, a large group of flagellate protists, are primarily responsible for the phenomenon when a dinoflagellate population increases to huge numbers. The water is discolored red or brown due to the presence of dinoflagellate cells numbering up to 20 million cells per liter. Red tides produce toxins that kill fish and make shellfish dangerous to eat. The toxins may also make the surrounding air difficult to breathe.

Symptoms of Red Tide

Red tide can cause:

  • Respiratory problems
  • Rashes
  • Irritation of the eyes, nose, throat, lips, tongue, and mouth.
  • Also, through consumption of infected sea organisms, such as shellfish, humans may devlop serious illnesses, such as paralysis.

Killer Protist #2:

Plasmodium (Plasmodium)

Also known as Malaria, this parasitic protist always has two hosts in its life cycle: a mosquito vector and a vertebrate host. Its vector, as mentioned before, is a mosquito, and that mosquito travels around, and, when it gets onto human skin, is transmitted via its saliva to the human bloodstream, where it grows, destroys, and infects red blood cells, old and new. There are an estimated 300-500 million cases of malaria each year.

Symptoms of Malaria

The stages of Malaria are:

  • a cold stage (sensation of cold, shivering)
  • a hot stage (fever, headaches, vomiting; seizures in young children)
  • and finally a sweating stage (sweats, return to normal temperature, tiredness).


The symptoms of Malaria are:

  • Fever
  • Chills
  • Nausea and vomiting
  • Body aches
  • Sweats
  • Headaches
  • General malaise

Deadly Protist #3:

Giardiasis (caused by Giardia lamblia)

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 (poop) from infected humans or animals.

Symptoms of Giardiasis

The symptoms of Giardiasis are:


  • diarrhea
  • abdominal pain, particularly cramping
  • bloating
  • nausea with or without vomiting
  • malaise
  • Fatigue

Killer Protist #4:

Sleeping Sickness (caused by Trypanosoma brucei)

Sleeping sickness, or African trypanosomiasis, is a disease. It is caused by a protozoan parasite, Trypanosoma brucei. The tsetse fly is the vector that spreads it. It is common in certain areas of tropical Africa. Today, around 30,000 people are infected with it.

Symptoms of Sleeping Sickness

Symptoms of this disease vary in two stages:


First Stage:


  • Bouts of fever
  • Headaches
  • Joint pains
  • Itching.



Second Stage:


  • Changes of behavior
  • Confusion
  • Sensory disturbances and poor coordination.
  • Disturbance of the sleep cycle, which gives the disease its name, is an important feature of the second stage of the disease. Without treatment, sleeping sickness is considered fatal although cases of healthy carriers have been reported.