Killer Protists

4 Protists that Cause Disease and Potential Deaths

Naegleria - Primary Amebic Meningoencephalitis


Naegleria fowleri

Primary Amebic Meningoencephalitis

How Someone Gets Sick

The parasite, Naegleria fowleri, also known as the "brain eating amoeba" causes a rare brain infection. The protist is typically present in contaminated water, more specifically in warm, freshwater bodies such as lakes and rivers. The infection occurs when the contaminated water enters the nose, carrying the parasite. Naegleria fowleri then travels from the nose, up into the brain where fatal incidents can take place. The traveling protist causes a disease entitled primary amebic meningoencephalitis, otherwise known as PAM. The protist can only travel up the nose, so a person will not get infected if the contaminated water is consumed.


The initial symptoms of the PAM disease include headaches, fever, nausea, and vomiting. However, these initial symptoms do not occur until about five days after the infection. In the later stages of the disease, symptoms include stiff neck, confusion, lack of attention to surroundings, loss of balance, seizures, and hallucinations. The protist acts quickly, usually causing death after about 5 days of experiencing the symptoms.

Toxoplasma gondii - Toxoplasmosis


Toxoplasma gondii


How Someone Gets Sick

Toxoplasmosis is a food-borne disease, so the host becomes infected from consuming anything infected by the parasite, Toxoplasma gondii. This can be caused by the consumption of undercooked meat, drinking contaminated water, or swallowing the parasite from the contact of cat feces.


The symptoms of the toxoplasmosis infection are similar to those of the flu, including swollen lymph glands and muscle aches. If the disease is severe, symptoms such as damage to the brain, eyes, and organs can occur. However, these severe cases are more common to people with weak immune systems, as it typically can be combatted through strong immune systems. Despite having a healthy immune system, the damage affecting the eyes can occur in some cases.

Plasmodium - Malaria


Plasmodium falciparum


How Someone Gets Sick

Malaria is caused by a parasite that infects a certain type of mosquito, an infective female Anopheles mosquito, which then infects the human host. For humans specifically, the parasite infects the liver cells where they grow, then in the red blood cells. The parasite then destroys the red blood cells, which cause the release of daughter parasites to destroy other red blood cells. Malaria can also be spread through blood transfusion and organ transplants because the parasite is found in red blood cells.


Malaria can cause the human host to suffer with high fevers, chaking chills, and symptoms similar to the flu. More symptoms include headaches, muscle aches, nausea, vomiting, and diarrhea. Malaria could typically be treated, but if it is not, kidney failure, seizures and mental confusion can occur. These symptoms typically then lead to death.

Giardia - Giardiasis


Giardia lamblia


How Someone Gets Sick

The parasite, Giardia causes the diarrheal disease called giardiasis. A person may be infected by the protist through the stool of an infected person or animal, which then must be swallowed. A person may also have a chance of being infected if water or ice is consumed that is contaminated. People are infected when they swallow the parasite and it is impossible for the disease to be spread through blood. Once infected, the parasite exists within the intestines, where it is then passed on to the feces.


The symptoms that occur result from problems in the intestines. They include diarrhea, gas, greasy stool, stomach cramps, nausea, and dehydration. These symptoms typically lead to weight loss.