Infection alters sleep

A team of biologists from the University of Münster has investigated whether and how the immune system can influence the behaviour of sticklebacks

It’s a well-known fact that if you don’t get enough sleep, you’re more likely to get sick. And it has also been observed that people sleep differently when they’re infected. Biologists from the Institute for Evolution and Biodiversity at the University of Münster have now investigated how a parasite infection affects the immune system and sleep in three-spined sticklebacks infected with their natural parasite, the tapeworm. One conclusion was that infected fish sleep longer after infection than their uninfected counterparts. However, the team only observed this difference one month after infection. In the first few days, there were virtually no differences. The results should help to deepen our understanding of the interactions between macroparasite infections, sleep and the immune response.

The research also shows that fish that were exposed to the tapeworm but not infected, because their immune systems had probably successfully fought off the parasite, slept less than those not exposed to the tapeworm. The team also found differences in the activity of genes responsible for the immune system and sleep in the brains of the fish, depending on which group the fish belonged to: infected, exposed to the tapeworm but not infected, or tapeworm-free.

"Our study is one of the first to show how macroparasites, i.e. multicellular parasites, can influence the sleep of their hosts," emphasised doctoral candidate Marc Bauhus. Previous studies have focused on bacterial and viral infections, mostly in mammals. They showed that infections can affect sleep, which is consistent with the current results of the Münster study. In the long term, these findings could also be relevant to biomedicine, for example in the treatment of sleep disorders or parasitic diseases.

About the methods: The team infected three-spined sticklebacks (Gasterosteus aculeatus) in the laboratory with the tapeworm Schistocephalus solidus and automatically recorded their behaviour fully with cameras to monitor activity and sleep phases. A mathematical model ("hidden Markov model") was used to objectively identify sleep patterns based on activity data. This new approach makes it easier to measure sleep in organisms where brain activity cannot be measured directly. "Strictly speaking, we are talking about sleep-like behaviour in fish because we are unable to measure the electrical activity of their brains underwater in a sleep laboratory as we can in humans. In fish, it is common in sleep research to use inactivity as an indication of sleep," explained Dr Robert Peuß. The activity (expression) of genes in the brain was analysed to understand which genes might be involved in the observed changes.

Original publication

Marc B. Bauhus, Sina Mews, Joachim Kurtz, Alexander Brinker, Robert Peuß, Jaime M. Anaya-Rojas (2024): Tapeworm infection affects sleeplike behaviour in three-spined sticklebacks. Scientific Reports 14, 23395: DOI: 10.1038/s41598’024 -73992-7