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parasites trypanosomes trypanosomiasis humans

Trypanosomes - A Weird Pathogen You Haven't Heard Of

Ever wonder what parasites are up to when they’re not bothering people? Take a look at the secret lives of parasites.

I am personally always enthralled to hear the stories of people who have lived lives with a diverse array of experiences, bouncing from career to career or country to country as they please, perfectly adapting to each new role. People like this are so impressive to me because of how they are able to re-create themselves to succeed in a number of environments, while many of us learn the rules and habits of one world, get comfortable, and stick to it.

What is more impressive than these people who adapt to different lifestyles are the parasites that have adapted to infect them. Most parasites by nature live in an array of different hosts throughout a single lifetime, and have to change their physical form drastically to be able to survive in these different environments.

Parasites do this all the time, and don’t get much recognition for it. Their well-developed flexibility is one of the most incredible, impressive, and mind-bogglingly frustrating things about these critters. Take Plasmodium, for example, the single-celled parasite that causes malaria. You probably know that in many countries, malaria is transmitted from mosquitoes to people. You also probably know that you (as a person) are really, really, remarkably different from a mosquito. Parasites like this have to adapt from living in one type of organism to another (and as a bonus, different organs within the hosts).

This is not a much more akin to the crazy-pants, unbelievable change of transforming from a fuzzy green larvae to a spectacular butterfly. Although, in this metaphor, the ‘butterfly’ causes malaria.

Another parasite that has to make big life changes is the African trypanosome. If you’ve never heard of such a thing, don’t feel too bad. Neither had I until recently, when I started doing research on the little guys. Now their mysterious inner workings possess a great deal of my mental capacity, and the maintenance of their health in my lab takes up a chunk of my time every day. In short, I promise they are a real thing (but don’t take my word for it, check out my citations!). Trypanosomes, like Plasmodium, are a single-celled parasite, but instead of being spread by mosquitoes, they are spread by an insect called the Tsetse fly. I promise this is also a real thing. Tsetse flies are found in Sub-Saharan Africa and have a painful bite.

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Fig. 1 Bloodstream-form trypanosomes among red blood cells (left) and a Tsetse fly at meal time (right) (https://www.cdc.gov/parasites/sleepingsickness/epi.html).

African Trypanosomes cause Human African Trypanosomiasis, or African Sleeping Sickness, in people, and they can also cause a devastating disease called nagana in cattle. Forms of this infection can be found in sub-Saharan countries including the Democratic Republic of Congo, Sudan, Central African Republic, Tanzania, and Uganda [1]. African Sleeping Sickness is also considered a neglected tropical disease [2]. Trypanosomiasis occurs in two phases. The symptoms first phase can include fever, joint pain, and headaches. The second of these phases includes more neurological symptoms that occur once the parasites cross the blood-brain barrier (one of their more impressive feats). These symptoms include confusion, disruption of sleep cycles (hence the name), changes in behavior, and loss of coordination [2]. This second phase has more symptoms that are specific to the disease, making it easier the easier stage to diagnose, however, treatment at this point can be difficult.

Without treatment, African Trypanosomiasis is fatal, and treatment in the second stage involves chemotherapies that can be painful and can cause adverse effects in patients [3]. Limited therapeutic options also contribute to drug-resistant strains of this parasite cropping up. Researchers work hard to understand these weird little organisms in order to find new and better ways to treat them. However, these processes take time, and are complicated by the diversity and adaptability of the parasite population. In the meantime it’s important to spread awareness of diseases such as these so they receive the funding and attention these problems require.

References:

[1] “Parasites – African Trypanosomiasis” Center for Disease Control. Last modified: August 29, 2012 https://www.cdc.gov/parasites/sleepingsickness/gen_info/index.html,

[2] “Trypanosomiasis, human African (sleeping sickness)” World Health Organization. Last modified: January 2017. http://www.who.int/mediacentre/factsheets/fs259/en/

[3] Lutje, Vittoria, Jorge Seixas, and Adrian Kennedy. “Chemotherapy for second-stage Human African trypanosomiasis.“ Cochrane Database of Systematic Reviews 8 (2010).

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