An epidemic of dengue fever of an intensity rarely known in Reunion; bats that recolonize the island two hundred years after their disappearance; zoonoses, animal diseases transmissible to humans, which are racing in the Indian Ocean … Even if the reasons for this crisis are many, most scientists point to climate change. It’s a fact: it has never been so hot on the island. “In fifty years, temperatures have increased by 1 ° C. And it’s been accelerating for a decade: 2019 broke all records, with + 1.2 ° C compared to the average of the last thirty years “, confirms François Bonnardot, head of the “studies and climatology” department at Météo France Indian Ocean. Now this increase “Promotes the spread of Aedes mosquitoes, important vectors of vector-borne diseases (malaria, dengue fever, chikungunya, West Nile fever, filariasis) in the intertropical zone”, warns the National Observatory on the effects of global warming.
This is the case in Reunion: since 2018, dengue fever has affected nearly 30,000 people, not counting undiagnosed patients, perhaps three times more numerous. The disease, which causes headache and fever, also killed 24 patients. Without common measure with the Covid-19, for which there were Wednesday “only” 425 cases and no deaths. Dengue fever occurs regularly in Reunion, as in 1978-1979, or even in 2004, but not at this level. Reine-Claude Carron, 59, hoarse voice and tired look, pays the price: the resident of Quartier-Français, on the East Coast, contracted the disease “Stack on Good Friday”. Paracetamol, lemongrass tea and citrus fruits soothed his pain, not his anger: “Before, we burned the leaves in the garden, the smoke scared away the mosquitoes; but the last time, the neighbors called the municipal police! ” The passion fruits, banana, coconut, guava and lychee from his garden grow best, the roots soaking in a stream. And the mosquitoes are having fun …
Sadly, even the tireless Josette Brosse, who created the Reunion Island association against chikungunya in 2006, is also a victim of dengue fever. The activist from Saint-Louis had escaped the mosquito during the terrible “curved back” epidemic, which had affected 240,000 people and caused more than 200 deaths. The person responsible was the tiger mosquito, which took advantage of global warming to colonize temperate countries, particularly in the south of the metropolis. At 72, Josette Brosse now suffers from muscle pain, severe diarrhea, and has lost “Eight kilos in five days”.
Another effect of global warming, according to François Chieze, director of surveillance and health security at the regional health agency, “The development of illnesses hitherto on stand-by, such as Rift Valley fever, in the Comoros and in Mayotte”. The disease, also transmitted by the mosquito, can cause hemorrhagic fever. It mainly affects zebus, goats and sheep, but 150 human cases were diagnosed last year in the French department. François Taglioni, university professor specializing in health risks, talks about climate change, but above all the destruction of the environment: “Forests are reservoirs of pathogenic organisms. By deforesting and dislodging animals, we encourage their circulation to humans. ” “Almost 60% of emerging diseases are of animal origin, adds Eric Cardinale, researcher at the Center for International Cooperation in Agronomic Research for Development (CIRAD) research center in Reunion. Of these, 70% are due to wild animals. ”
In Madagascar, a neighboring country of Reunion, pneumonic plague appeared in 2017, transmitted by rats driven from their nest by slash and burn crops. In Reunion, bats, disappeared from the island for two hundred years, suddenly reappeared. Chased in Mauritius, they took advantage of an intense cyclone to cross the 200 kilometers that separate the two islands. Climate change is precisely leading to a “Widening to the south of the cyclonic belt, towards Reunion”, recalls François Bonnardot, from Météo France. These three-foot-long black dogfish are being watched because the animal can transmit zoonoses, as seems to have been the case in Asia with the Covid-19. The bat is further “A natural reservoir of the Nipah virus”, recalls Eric Cardinale. This virus had caused hundreds of deaths in Asia in the 2000s, especially among pig breeders. However, this return of bats to Reunion would be “a chance”, to believe Sarah Fourasté, project manager at the Chiroptère Indian Ocean Group. “The fruit bat participates in the pollination and the dispersion of seeds of endemic trees of the island”, welcomes the ecologist. Best of all, bats can eat up to 25% of their weight in insects, including mosquitoes, which are responsible for many of the emerging diseases! Bats are also protected species in France; It is therefore enough, recommends Sarah Fourasté, to “Limit contact with humans”…
Laurent Decloitre corresponding to Reunion