“Okay, this is it,” Filipa Rijo-Ferreira thought after hearing some neuroscience presentations. She’d spent a year as a technician in a lab studying sleeping sickness but had never understood why no one studied the way in which the sickness affected the brain. But for this particular disease, it seemed important to study neuroscience and parasitology together. “I’m just going to make my own project.”
Through a unique Ph.D. program in her native Portugal, she was able to combine both fields of research, working with co-advisors on two continents to study the circadian rhythms of parasites. It’s well-known that parasites have rhythms — schistosoma emerge at the time of day when they’re most likely to encounter a host; sleeping sickness parasites scramble their host’s sleep cycle. But did these parasites’ rhythms derive from their hosts’ circadian rhythms, or from their own internal clocks?
Rijo-Ferreira found that 80% of the malaria parasites’ genes were being expressed in the bloodstream of their host at a specific time every day, even if she and her colleagues blocked light-triggered circadian rhythms that might give the host animal a sense of day and night. When they repeated the experiment in mice that didn’t have the genes to make their own internal clocks, they found that 60% of the parasitic genes were still being expressed at one time of day, showing that the malaria parasites themselves had an internal clock.