Montpellier: A Pioneer in Parasitic Ecology
To better manage the effects of parasites on human health, we need to understand how they fit into their ecosystem. This is the focus of parasitic ecology, a discipline that originated at the University of Montpellier through the work of Louis Euzet.
It is a very strange living organism. It uses another living organism, called a host, as its habitat and source of energy. Parasites can cause human diseases, some of which are serious: malaria, schistosomiasis, dengue fever, and chikungunya. To control these diseases, doctors cannot do without the contributions of researchers in parasitic ecology. Their work: “ understand how parasites move through ecosystems, analyze their relationships with their hosts, and identify the factors that influence their evolution “explains Catherine Moulia, a research professor at the Institute of Evolutionary Sciences in Montpellier (ISEM).
While researchers around the world now practice this discipline, it owes much to the work of Professor Louis Euzet, who headed the Laboratory of Comparative Parasitology at the University of Montpellier 2 from 1969 to 1990. As the founder of the “Montpellier School of Parasitology,” he, along with his student Claude Combes, is considered one of the pioneers of this field of parasitic ecology, one of whose goals is to understand the evolutionary aspects of host-parasite interactions. “ Our teams in Montpellier— ISEM, MIVEGEC, and others—are the successors to the Euzet-Combes School “Catherine Moulia points out.”
When the parasite takes control
Students in Louis Euzet’s laboratory were thus among the first to demonstrate that parasites could alter their host’s behavior to increase their chances of being transmitted to another host.“This is what is known as the ‘favoritism phenomenon,’” explains Alain Lambert, Professor former Professor retired who spent his career at UM2 alongside Louis Euzet. Example: the small liver fluke. During its life cycle, the small liver fluke first parasitizes an ant. To continue its cycle and reach adulthood, it must then parasitize a sheep.
Problem: how does it move from one host to the other, given that sheep aren’t particularly fond of ants? The liver fluke has found a fascinating solution: it alters the ant’s behavior so that, instead of going about its business around the anthill with its fellow ants, it perches atop a blade of grass to increase its chances of being eaten by a sheep grazing nearby.“The parasite takes control of its host’s brain,” summarizes Alain Lambert.“Combes has shown that an entire segment of the food chain is controlled by parasites,”explains Laurent Gavotte, Professor ISEM. “This is a key finding for the management of populations and ecosystems.”
Cut off communication between the host and the parasite
And when it comes to combating human diseases, having the most detailed understanding possible of the parasite’s life cycle and its interactions with its host is crucial. Researchers have thus succeeded in limiting the transmission of schistosomiasis, a tropical disease that has long plagued Guadeloupe.“The goal is not to eradicate the schistosome, the parasite responsible for this disease, but to implement public health measures to prevent people from coming into contact with the waters where these parasites live,” explains Catherine Moulia.“This amounts to breaking the transmission chain between the host and the parasite.” Similarly, malaria, which was rampant in France—and in the Hérault region in particular—was eradicated after the war. How?“By draining larval breeding sites and widely implementing the use of quinine,” explains Alain Lambert.
But the disappearance of a parasite is sometimes not without consequences for its host.“There are areas in Africa where both intestinal worms and a severe neurological form of malaria are prevalent. We found that children who had received treatment to eliminate these worms were much more likely to contract neuro-malaria, which is far more dangerous,” explains Laurent Gavotte. It is therefore vital to understand the cross-interactions between parasites in order to best treat the resulting diseases.
Finding environmental solutions
“The contribution of non-medical scientists is crucial to understanding these interactions,” emphasizes Catherine Moulia. Researchers are increasingly sought out by doctors, who need a more comprehensive view of the situation.“We need a multifactorial approach that involves understanding each system and each environmental context,” explains Alain Lambert.“And taking into account changing global dynamics,” adds Laurent Gavotte. This was one of Louis Euzet’s fundamental contributions: moving beyond the medical framework to provide a broader perspective. Today, researchers in parasitic ecology are focused on finding sustainable environmental solutions.“We never completely eradicate a parasite,”explains Catherine Moulia, “we try to keep it at a manageable level to limit the impact—particularly the economic impact—of the diseases associated with it.” It is a never-ending task in an environment in constant flux. Parasitic ecology and its offshoot, epidemiology, have a bright future ahead of them…