Protist diseases are diseases caused micro These disease-ca microorganisms are called pathogens and can include viruses, bacteria fungi, and protists. Anyone can become infected by a pathogen, which can be spread through direct contact with contaminated objects or sick individuals. Some of the most dangerous pathogens are bacteria and viruses, but protists and fungi are also capable of causing serious illnesses. Inanimate objects that can spread disease are called fomites. To learn about other types of pathogen-causing diseases, check out our articles on bacterial, viral, and fungal diseases.

What are protists?

Protists are a diverse group of eukaryotic organisms that include protozoans and algae like seaweeds. They are single-celled or cluster of similar cells that have a nucleus. These eukaryotes are not plants, animals or fungi, but they have structures in the cytoplasm that are surrounded by membranes. Although only a few protists are pathogenic, the diseases they cause are serious, such as malaria. They often require a vector, like the Anopheles mosquito, to transfer from one host to the next. Vectors play a vital role in transmitting pathogens. Hosts are organisms that carry the pathogenic agent, while vectors are organisms that spread infection by transmitting pathogens from one host to another. To learn more about eukaryotes and prokaryotes, check out our article types of organisms!

What are the different types of protists?

Protists are a diverse group of organisms that can have more similarities with organisms from other kingdoms than with one another. For example, algae can be considered plants rather than protists. Protists can be divided into three main categories based on their characteristics: plant-like, animal-like, and fungus-like.

Plant-like protists live in various environments like soil, freshwater, saltwater, or bark, and produce oxygen. They include euglenoids, dinoflagellates, diatoms, and algae such as green, red, and brown algae.

Animal-like protists are known as protozoans, which means "first animals." They are unicellular and categorized based on their mode of movement. Examples include those that move by cilia, flagella, or amoeboid movement.

Fungus-like protists have cell walls and reproduce by forming spores similar to fungi. Examples include water molds and slime molds. The diversity of protists is vast, and their characteristics and behaviors vary widely.

Protist diseases in humans

There are several diseases exemplified below that are caused in humans by protist pathogens. The most relevant and lethal today by far is malaria which remains one of the biggest causes of death in the developing world.

Malaria

Malaria is a disease that spreads through the bites of female Anopheles mosquitoes. These mosquitoes act as vectors and transmit the pathogenic agent Plasmodium falciparum, which is an animal-like protist. Mosquitoes carry the parasite without being affected by the disease. Malaria is prevalent in regions with high temperatures, such as Africa, Asia, South and Central America.

The transmission of malaria requires infection in both humans and mosquitoes. Plasmodium multiplies inside both hosts, increasing the chance of infecting other mosquitoes and humans. Its life cycle has two stages: a sexual stage in the mosquito and an asexual stage inside humans.

When the malaria parasite enters the bloodstream, it initially targets the liver cells, followed by red blood cells, where it multiplies. Most of the pathological symptoms of malaria result from the infection of erythrocytes or red blood cells. During this stage, the parasite repeatedly destroys the red blood cells and invades other red blood cells cyclically.

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Malaria can cause various symptoms and is divided into uncomplicated and severe (complicated) disease. The incubation period for malaria symptoms to appear can range from a week to a year, but on average, it takes 10-15 days. Symptoms include fever, sweats, chills, headaches, vomiting, and diarrhea.

Malaria is treatable and curable, and early diagnosis and treatment are essential to reduce malaria incidence and deaths. Antimalarial drugs like quinine and chloroquine prevent the parasite from growing and spreading within the body by inhibiting protein synthesis. Artemisinin-based combination therapy (ACT) is currently the best treatment available, especially for Plasmodium falciparum infection.

Preventive measures for malaria include vector control strategies, such as reducing mosquito populations and avoiding mosquito bites by using mosquito nets and wearing insect repellent. The first approved malaria vaccine, RTS,S (Mosquirix), has been recommended by the WHO for use among children since late 2021. It acts against Plasmodium falciparum and significantly reduces severe malaria disease in children.

Sleeping sickness

Like malaria, sleeping sickness disease is spread via a vector. The Tsetse fly is a species native to Africa and it spreads a protist disease called sleeping sickness, also known as Human African trypanosomiasis. This disease is caused by protists microorganisms of the species Trypanosoma brucei. (animal-like protist) The Tsetse flies are found only in sub-Saharan African countries and it's the people who live in the rural parts of Africa that are most affected.

When the fly bites a person, the bite develops into a red sore and the person develops a fever, muscle and joint ache, swelling in the lymph glands, irritation and headaches. It is a disease that attacks the central nervous system. Other symptoms include: Seizures Personality changes. Alteration of sleep patterns. Difficulty in walking and talking. If these symptoms are not treated, the disease will worsen and can be fatal within months.

Giardiasis

Giardiasis is a diarrheal disease caused by a small parasite protozoan called Giardia that can be found in contaminated soil, food, or water. Swallowing Giardia can result in giardiasis, which can be easily transmitted from person to person, as well as through polluted water, food, surfaces, and items. The most common way for people to become ill is by drinking or coming into contact with contaminated water.

Symptoms of giardiasis include smelly diarrhea, tummy pain or cramps, flatulence, dehydration, and weight loss. Giardiasis can be treated with antibiotics and prescription drugs.

Amoebic disyenteria

Entamoeba histolytica is a protozoan parasite that causes amoebic dysentery or amebiasis. It's transmitted through contaminated drinking water or anything that has come into contact with infected faeces. Symptoms include fever, chills, diarrhea, and abdominal discomfort, and only 10-20% of people become ill after infection. Treatment involves antibiotics, IV fluids, and medication to control diarrhea, nausea, and vomiting.

Downy mildew is a protist disease that affects many plants and is spread by spores that can remain dormant in the soil for several years. It's caused by different types of protists that infect leaves and can affect the yield and quality of crops as well as the appearance of ornamental plants. Symptoms include mould-like growth on the underside of the leaf, discoloured blotches on the upper leaf surface, and severely affected leaves may shrivel and turn brown. Crop rotation can help avoid reinfection. Spores are reproductive cells produced by some organisms that can originate a new individual without fusion with other reproductive cells.

Control of Downy mildew

To summarize, protists are a group of eukaryotic organisms that can cause infectious diseases in humans, animals, and plants. Examples of protist diseases include malaria in humans and downy mildew in plants. Non-chemical control strategies, such as crop rotation, removing affected leaves, and improving air circulation, can be used to manage protist diseases in plants.

Protist Diseases

How do protists cause disease? 

Usually by being spread through vectors (an organism that does not cause disease itself but which spreads infection by conveying pathogens from one host to another). 

What are three examples of protists? 

Animal-like Protists; Fungus-like Protists; Plant-like Protists

How are protist diseases treated? 

Mostly through preventative measures. Malaria prevention includes using mosquito nets and insecticides while in downy mildew, crop rotation is recommended.  

What is a protist disease? 

A disease caused by protists which are a group of eukaryotic, usually single-celled organisms of the kingdom Protista.

Is malaria a protist disease? 

Yes, it is caused by the plasmodium protist.

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