What Diseases Do Protists Cause?

Before getting to know “what diseases do protists cause”, let us first try to consider “what exactly are protists”. Protists are unicellular organisms that are not animals, fungi or plants. Instead, they are a diverse group of eukaryotic microorganisms.

Protists tend to remain in environments containing liquid water. Their natural function of these organisms is to serve as primary producers in ecosystems, especially in oceans. On the other hand, they also cause certain diseases in humans. Some common diseases caused by protists are:


Malaria is an infectious disease caused by protists of the Plasmodium genus. This mosquito-borne disease is prevalent in tropical and subtropical regions, particularly the areas below the Sahara Dessert in Africa.

The disease causing protista when enter the blood stream of a human being, it travels through the liver and matures, invades and multiplies within the red blood cells. Gradually, symptoms like fever, chills, excessive sweating, malaise, diarrhea, vomiting etc develop.

African Sleeping Sickness

African Sleeping Sickness or Trypanosomiasis is tsetse fly borne parasitic disease caused by the protists of Trypanosoma Genus. Tsetse flies are mostly found in sub Saharan Africa.

The disease may be present in the form of chronic infection (due to Trypanosoma brucei gambiense) but without the manifestation of any serious symptoms.

The symptoms of the disease tend to appear in its advanced stages when the central nervous system is affected. When this disease is present in the form of acute infection (due to Trypanosoma brucei rhodesiense), it manifests the symptoms with a few weeks or months of the infection and develops rather rapidly.

American Trypanosomiasis or Chagas disease

This disease is another form of African Sleeping Sickness. It occurs in 15 Central and South American countries due to the protozoan parasite Trypanosoma cruzi.

The disease is usually transmitted through blood sucking triatomine bugs or through skin breaks, mucous membranes, contaminated food, blood transfusion, organ transplantation etc.


In acute stages, it causes mild symptoms but in chronic form it causes symptoms related to the nervous system, digestive system and the heart.

Amoebic Dysentery

As the name suggests, this disease is caused by amoeba Entamoeba histolytica. It is transmitted through the ingestion of contaminated food or water. It is more common in developing countries.

This intestinal infection results due to the formation and consequent bursting of infective cysts containing protists within the large intestine.

Free amoebae that do not form infective cysts tend to die in the acidic environment of the stomach. The disease is characterized by symptoms like painful bowel movements, peritonitis, bloody diarrhea, vomiting etc.


Giardiasis, an infection of the small intestine is caused by protists known as Giardia Lamblia. The disease is more common in developing countries as compared to the developed countries. It causes symptoms like cramps, diarrhea, fatigue, weight loss and other similar symptoms.

The disease is generally spread though ingestion of contaminated water. A variety of aquatic or semi aquatic wild mammals such as beavers, small rodents, muskrats etc may also spread this disease to humans.


Babesiosis is a parasitic infection caused by protists of Babesia genus. The disease is transmitted through the bite of Ixodus tick, that also causes Lyme disease. Contaminated blood transfusion may also result in the same.

Most of the cases of Babesia are asymptomatic. However, when the symptoms are present, they are similar to the symptoms of Malaria.


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