Tiny bugs live in the blood.
They move like a corkscrew. A small fly can pass them to you. They can make people feel very sleepy.
This matters for our health. Have you ever seen a fly?
Tiny bugs live in the blood.
They move like a corkscrew. A small fly can pass them to you. This happens when the fly bites a person or an animal.
These bugs can make people very sleepy. This is called sleeping sickness.
They also make cows and horses sick.
A man named David Bruce found them. He looked at the blood of sick cows. He found the tiny bugs in 1894.
The bugs have a long, thin body. They have a tiny tail to help them move. This tail is called a flagellum.
Scientists still work to find new ways to help. They want to make better medicine for sick people.
Trypanosoma brucei is a tiny parasite. It lives in sub-Saharan Africa.
These parasites live in blood and body fluids. They do not live inside cells. They move like a corkscrew. This name comes from Greek words for "borer body."
These parasites cause serious sickness. In humans, it is called sleeping sickness. In cattle and horses, it is called nagana.
A tsetse fly passes the parasite from one host to another. This happens when the fly bites to drink blood.
David Bruce found these parasites in 1894. He looked at the blood of sick cows.
There are three main types of this parasite. One type is very common in central and western Africa. It causes a slow sickness. Another type causes a fast sickness.
The parasite has a long, thin body. It is 8 to 50 micrometers long. A micrometer is a very small unit of measure. It has a tail called a flagellum. This tail helps it move. It also has a part called a kinetoplast. This part holds many circles of DNA.
Trypanosoma brucei is a tiny living thing called a parasite. It lives in the blood and body fluids of animals in sub-Saharan Africa.
Most parasites like to hide inside cells, but this one stays outside of them. It can cause very serious diseases that can be deadly. In humans, the sickness is called African trypanosomiasis, or sleeping sickness. In animals like cattle and horses, the disease is called nagana.
This parasite is a major problem for people and animals in many parts of Africa.
The parasite moves from one living thing to another using an insect. This insect is called a tsetse fly. The fly carries the parasite and passes it on when it bites to drink blood.
As the parasite moves between the fly and a mammal, it goes through many changes. Its shape and form change to survive in different bodies. Once inside a human, the parasite uses special proteins on its surface to hide. These proteins change constantly so the body's immune system cannot find them. This clever trick helps the parasite stay in the body for a long time.
People have known about these sicknesses for a very long time. Ancient Egyptian writings even described sleeping sickness in animals. In the 1800s, the disease was a huge problem in southern and eastern Africa. A doctor named John Atkins gave the first medical description of human sleeping sickness in 1734. Later, in 1803, Thomas Masterman Winterbottom described important symptoms like swollen nodes in the neck. He called this "Winterbottom's sign."
These early doctors helped people start to understand the sickness.
Sir David Bruce discovered the actual parasite in 1894. He was a captain in the army and a professor of pathology.
He and his wife, Mary Elizabeth Bruce, went to Ubombo Hill to study nagana. On the sixth day, David found the parasites in the blood of sick cows. He proved they were the cause of the disease. Scientists later named the genus Trypanosoma after the Greek words for "borer body." This name describes how the parasite moves like a corkscrew. The specific name honors David Bruce for his hard work.
The parasite has a very unique shape and structure. It is a single cell that is between 8 and 50 micrometers long.
It has a long, tapered body that is very streamlined. One part of the cell is called the kinetoplast, which holds thousands of circles of DNA. It also has a tail called a flagellum that helps it swim. This parasite is special because it is one of the few that can cross the blood-brain barrier. This makes the disease very hard to treat with current medicines.
Trypanosoma brucei is a complex species of parasitic kinetoplastid found in sub-Saharan Africa. Unlike many other protozoan parasites, it does not live inside host cells. Instead, it is exclusively extracellular, meaning it lives in the blood plasma and other body fluids. This parasite is responsible for causing two deadly vector-borne diseases. In humans, the infection is known as African trypanosomiasis, or sleeping sickness. In animals like cattle and horses, the disease is called nagana.
The parasite moves between mammal hosts using an insect vector called the tsetse fly, or Glossina. Transmission occurs when the fly bites a host to take a blood meal. During this process, the parasite moves from the fly into the mammal, or vice versa. The parasite undergoes complex morphological changes, which are changes in shape and structure, to survive these different environments. Once in the mammalian bloodstream, the parasite uses a clever survival method called antigenic variation. It uses variant surface glycoproteins on its cell surface to constantly change its appearance. This allows it to evade the host's adaptive immunity, leading to a chronic infection.
Scientists classify T. brucei as a species complex consisting of three distinct subspecies. The first is T. b. brucei, which infects non-human mammals and causes nagana. The other two are zoonotic, meaning they can infect both humans and animals. T. b. gambiense causes a slow-onset chronic form of sleeping sickness and is most common in central and western Africa. It is responsible for about 98% of all human cases and is nearly 100% fatal without treatment. The third subspecies, T. b. rhodesiense, causes a fast-onset acute form of the disease. It is prevalent in southern and eastern Africa, where game animals and livestock serve as the primary reservoir.
Humanity has observed the effects of this parasite for many centuries. Ancient Egyptian writings included descriptions of sleeping sickness in animals. In 1734, John Atkins provided the first medical description of human sleeping sickness in Guinea. Later, in 1803, Thomas Masterman Winterbottom described swollen lymph nodes in the neck, a symptom known as Winterbottom's sign. The parasite itself was discovered in 1894 by Sir David Bruce. Working at Ubombo Hill with his wife, Mary Elizabeth Bruce, he identified the parasites in the blood of diseased cows. The genus name comes from Greek words meaning "borer body," describing its corkscrew movement.
Research into the parasite's life cycle was a major scientific effort involving many teams. In 1902, a Sleeping Sickness Commission was formed to investigate an epidemic in Uganda. This epidemic was severe, with an estimated death toll of 20,000 people, and eventually killed more than 250,000 people over two decades. While early investigators struggled, David Bruce eventually established that the tsetse fly was the transmitter. Later, in 1909, Friedrich Karl Kleine discovered that the parasite has developmental stages within the fly. Finally, Muriel Robertson established how the parasites reach the salivary glands of the fly between 1911 and 1912.
At a microscopic level, T. brucei is a single-celled eukaryotic organism. It measures between 8 and 50 micrometers in length and has a streamlined, tapered body. Its cell membrane is called a pellicle, which protects organelles like the nucleus and mitochondria. A unique feature of this parasite is the kinetoplast, an organelle containing thousands of interlinked circles of mitochondrial DNA. This kinetoplast sits near the basal body, which is the starting point for the flagellum. The flagellum is a tail-like structure that allows the parasite to swim through body fluids.
Understanding T. brucei is critical because it is one of the few pathogens that can cross the blood-brain barrier. This ability to enter the central nervous system makes the disease particularly dangerous. Currently, there is an urgent need for new drug therapies. Existing treatments can have severe side effects and may even be fatal to the patient. Because the subspecies are so closely related, scientists use molecular markers to tell them apart. For example, the SRA gene helps identify T. b. rhodesiense, while the TgsGP gene is specific to certain T. b. gambiense strains.
Where will your curiosity go next?
🖼️ Images & Media (6)
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.