Blog post: Beyond thoughts – Sanctuary for Parasites
By- Praveena R G Chandrasegaran
Our brain plays an important role in controlling our every move, but did you know that it can also serve as an unexpected hideout for parasites? A protective membrane in the brain, called the blood-brain barrier, is a formidable shield, that selectively permits access to our nervous system.
Despite this defence, elusive intruders like the African trypanosome can enter our brain with its peculiar skill - to hide behind the protective layers of the blood-brain barrier within our nervous system.
African trypanosome causes trypanosomiasis, famously known as sleeping sickness. Typically transmitted by the bite of an infected tsetse fly, it is more common in rural areas.
While it’s still uncertain whether these parasites can pass through the blood-brain barrier, research suggests that some types of sensory neurons might provide a conducive environment for their growth. Areas densely supplied by these neurons, like ganglia neurons (clusters of nerve cell bodies outside the brain and spinal cord), could potentially become a refuge for these parasites, enabling their survival.
The clinical manifestations of this invasion by the parasites, include sensory, motor, and mental disturbances. However, what sets this parasitic infection apart is its profound impact on sleep, aptly named “sleeping sickness”. This disease induces alterations in our sleep patterns.
These parasites manipulate our circadian rhythm, the precise mechanisms of which remain a mystery. One hypothesis proposes that inflammation in part of the brain which is responsible for circadian rhythm, including sleep-wake cycle, may result in disruptions. This cascade of events could then disrupt the circadian timing and sleep-regulatory systems, leading to the unique sleep disturbances observed in sleeping sickness.
It is important to note that the sleep-wake regulation disruptions seen in sleeping sickness are not typical for infectious diseases. This peculiar characteristic further highlights a complex relationship between the parasites and our brain that continues to baffle scientists as they delve into the mysteries of this ‘neuro-parasitic invasion’. The brain, it seems, harbours not only our thoughts but also a cosy realm for parasites to survival and hideout.
Author bio: Praveena (she/her) is a first-year PhD student at the Roslin Institute. She is studying the host immune responses to infection of Toxoplasma gondii, a unicellular parasite, in both pigs and humans.
Image Credit: The tsetse fly is the insect that carries African trypanosomiasis, or sleeping sickness. (Photo by Geoffrey Attardo, assistant professor, Department of Entomology and Nematology, University of California Davis).