The Unusual Sleeping Sickness Parasite or Trypanosoma

Trypanosoma is a microscopic and unicellular parasite of humans and other animals. It can produce some very serious effects, but it’s a fascinating organism with some unusual characteristics. In humans, two species of Trypanosoma cause the disorder known as sleeping sickness. One of the symptoms of this disease is daytime sleepiness and disruption of sleep patterns at night. The disorder can be treated, although the drugs that are used are often quite toxic. If it’s not treated, the disease is very often deadly.

Trypanosoma sp.
Photo credit: CDC/Dr. Myron G. Schultz

Sleeping Sickness

Sleeping sickness is technically known as trypanosomiasis. It’s sometimes called African sleeping sickness because it occurs in the continent of Africa. Two subspecies of Trypanosoma brucei cause the illness: T. b. rhodesiense (which causes East African sleeping sickness) and T. b. gambiense (which is responsible for West Africa sleeping sickness). The latter organism causes most cases of the disease.

The parasite requires both a human and a tsetse fly (genus Glossina) in order to complete its life cycle. One of the common symptoms of sleeping sickness is a sore in the area where the fly bites, which is sometimes known as a chancre. Other common symptoms include a fever, headache, aching muscles and joints, a skin rash, and swollen lymph nodes. If the parasite invades the central nervous system, confusion, personality changes, and extreme fatigue may appear.

The effects are slightly different in the two types of sleeping sickness. The East African variety develops faster and if untreated can lead to an earlier death. A doctor’s diagnosis is required to confirm the presence of either form of the disease and to prescribe treatment.

The Trypanosoma Parasite and the Kinetoplast

In its mature form, Trypanosoma has an elongated cell with a tapered shape. It moves by beating its flagellum, or the whip-like appendage extending from its cell. It exists in specific forms in its insect host and in its human host and has a complex life cycle. Tsetse flies feed on human blood and pass the parasite to people while feeding on them.

Trypanosoma is sometimes referred to as a kinetoplastid. Kinetoplastids are organisms that contain a special structure in their mitochondrion known as a kinetoplast. Trypanosoma has a single and very large mitochondrion. The mitochondria are the organelles that produce energy. They are the only cellular location of DNA outside the nucleus in either the parasite or us. Unlike the parasite, we have numerous mitochondria in our cells.

The kinetoplast looks like a large and very dense granule in electron micrographs. It contains kinetoplast DNA or kDNA. This exists as a network of interlocking large and small mitochondrial DNA rings. The interesting arrangement is often said to resemble chain mail. RNA is also present in the kinetoplast. The nature, behaviour, and function of the structure are still being investigated.

Evading the Immune System With a Protein Coat

One reason why Trypanosoma is such a potent pathogen is it has the ability to evade our immune system. Its cells are covered by identical proteins. Our immune system recognizes these proteins as inappropriate for our body and destroys the parasite. This sounds like it should be the end of the story and the problem, but the parasite has a very useful feature that protects it from the immune system.

The proteins borne by the parasite are known as variable surface glycoproteins, or VSGs. A glycoprotein is a protein with attached carbohydrates. The proteins cover the cell membrane of the parasite in a dense, tightly-packed layer that prevents the immune system from attacking the membrane.

Occasionally, the parasite changes the identity of its VSGs. As is true for other proteins, the code for making VSGs is found in the genes located in the DNA of the nucleus. Trypanosoma has many VSG genes, each coding for a different protein. During an infection, parasite cells that haven’t yet been killed by the immune system activate a different VSG gene and make different surface proteins. One researcher likens the process to putting on a different coat. The antibodies produced by the immune system don’t recognize the new coat and the parasite concentration builds up again. Understanding the details of the process could be useful in improving the treatment of the disease.

Dealing With the Disease and the Parasite

Ideally, sleeping sickness either wouldn’t exist or every incidence of the disease would be quickly and successfully treated. From a biological point of view, however, the parasite that causes the disease is a very interesting entity. The scientific study of its complex life cycle, cell structure, and behaviour might help us to understand not only the parasite's biology but also the biology of other cells, including those of humans.

References

Sleeping sickness from the CDC (Centers for Disease Control and Prevention)

Facts about kinetoplasts from Tulane University

Trypanosoma camouflage from the phys.org news service

Two Captive Belugas Will Go to a Sea Sanctuary

Little Grey and Little White are twelve-year-old beluga whales living in an aquarium in China. In the spring of 2019, if all goes according to plan, they will be transported to Iceland to live in a sanctuary. The plan may sound wonderful to people opposed to keeping belugas in captivity. There are some concerns associated with it, however. The transfer will be a major undertaking that will likely involve a considerable amount of stress for the animals. The belulgas' new home should be much better than their old one, but it will have some limitations. It will also present some new environmental challenges for the animals.

The head of a beluga whale
Steve Snodgrass, via Wikimedia Commons, CC BY 2.0

Beluga Whales

Belugas live in the Arctic and the Subarctic. Unlike most whales, some belugas enter rivers. They are white as adults and have no dorsal fins. They have a large, fatty melon in the front of their head, which plays an important role in echolocation. During this process, the whales produce sounds that are focused by the melon and sent into the environment. The melon changes shape during this activity. The sound waves bounce off objects and return to the whales, giving them detailed information about their surroundings. Another interesting feature of the beluga is the fact that its neck vertebrae aren't fused, giving it the ability to turn and nod its head.

Belugas are social animals and feed on both fish and invertebrates. They are sometimes known as sea canaries because they're so vocal. The animals emit chirps, squeals, grunts, whistles, and other sounds. They generally live from forty to sixty years.

A Sanctuary With a Sea Pen

Since Little Grey and Little White's new home is being referred to as an "open-sea sanctuary",  some people seem to think that the belugas are being set free. This isn't the case,  however. The whales will be placed in a sea pen in an ocean inlet. The pen will have an area of 32,000 square metres and a depth of 10 metres (which doesn't sound very deep to me). This is certainly larger than the whales's current tank, but the pen is still an enclosure. It will be exposed to the cold water and tides in the area by netting of some kind, which explains the "open water" designation. The facility will have a visitor centre and a care center for the whales. The organizers say that the belugas can't be released into the wild because they depend on humans for their care.

A captive beluga
Carquinyol, via Wikiimedia Commons, CC BY-SA 2.0

Ocean World and Iceland

The whales currently live in Shanghai in the Changfeng Ocean World aquarium. The facility is owned by Merlin Entertainment. The move is being arranged by an organization called Sea Life Trust in cooperation with Merlin. The original plan was to transport three belugas to Iceland. Since then, one of the whales (Jun Jun) has died. The sea pen will be located at Klettsvik Bay in the Westman Islands off the coast of Iceland. This area was also the location for the Free Willy movie. The pen is currently being created and should be ready by March of next year.

Training

The belugas are undergoing "training" for life in their new home. Their enclosure will be longer, wider, and deeper than their current one. Trainers are trying to build up the animals' strength so that they can deal with currents and tides and can dive in their new habitat. They are giving them more calories to eat in order to build up blubber to protect them from the cold. The whales are also being introduced to the stretchers that will carry them during transport.

The Journey

The journey to Iceland will take thirty-five hours and cover 8,000 kilometres. The whales will be accompanied by veterinarians and other experts. At the end of their trip they'll find a larger and more natural home. If the trip is successful, it may encourage other facilities to release their whales and dolphins into sea pens. While a pen is not as good as freedom, it could be much better than an aquarium tank.

Will the Effort Be Worthwhile?

I think it's wonderful that the whales will no longer have to perform and will have a larger swimming area. The trip to Iceland will likely be stressful, though. I hope the size of the pen and the new environment will make the effort and stress worthwhile and that the belugas are much happer in their new home.

References

World's first sanctuary for belugas from New Scientist

A beluga sanctuary in Iceland from the Canadian Broadcasting Corporation

Whales in training from the Iceland Review