“800,000 Viruses of Animal Origin: Future Threats to Human Health”

At nightfall, in a forest in Yucatan (southeastern Mexico), veterinarian Omar Garcia collects fluids from a bat using a headlamp as part of a research program on zoonoses, these diseases which pass from animals to humans, such as perhaps Covid-19. Caught in nets, motionless in the hands of the veterinarian, the bat is a species considered to be a virus reservoir.

Omar Garcia collaborates in a Franco-Mexican scientific research program on zoonotic pathogens (viruses, bacteria, parasites) at the origin of numerous epidemics in recent decades in tropical areas, such as Ebola for example.

Regarding Covid-19, scientists widely believe that the pandemic started because an animal transmitted the virus to humans, probably in the Chinese market of Huanan, in Wuhan. Researchers and US officials, however, defend the hypothesis of a laboratory leak, which China disputes.

In any case, the threat and the risks have not disappeared: it is estimated that between 500,000 and 800,000 viruses of animal origin could affect humans. On the strength of this figure, scientists from the Institute for Research and Development (IRD) and the National Autonomous University of Mexico (Unam) chose Yucatan, a tropical zone at risk like elsewhere in the world (Central Africa, Asia southeast).

With significant deforestation problems, two hours by plane from a megalopolis connected to the whole world, Mexico City, the Yucatan presents itself as “a very emblematic region of the risks of emergence of zoonosis”, underlines Benjamin Roche, researcher and director at the IRD, and co-director of the Franco-Mexican Eldorado laboratory in Mérida.

In theory, this laboratory can share its “experiences and good practices” with other research centers elsewhere in Latin America, Central Africa or Southeast Asia. This is in any case the aim of the French initiative Prezode (preventing the emergence of zoonotic diseases) which brings together 22 countries. The objective of the Franco-Mexican mission is to understand how pathogens, which circulate between animals, birds, rodents and mosquitoes, can potentially affect humans, explains Audrey Arnal, researcher at the IRD.

It is a question of “understanding what the consequences of contact between humans and wild fauna could be, and understanding what could be the next epidemic likely to emerge from nature”, she adds. “We have a lot of questions,” adds Maria José Tolsa, biologist at Unam, stressing that the Covid-19 pandemic has highlighted the research she has been carrying out for ten years.

Fieldwork begins in the early morning with the laying of nets to capture birds and bats. Then comes the taking of blood or other fluids by the scientists who identify the animal and record data, before releasing it. Then comes the time for analysis, on site in Mérida in the Franco-Mexican Eldorado laboratory, or in Mexico City.

“Among birds, we found species identified as a reservoir for West Nile virus (arboviruses mainly transmitted by mosquitoes that can cause neurological damage in humans)”, explains Rosa Elena Sarmiento, from the virology laboratory of the veterinary faculty of Unam.

In a later step, the team plans to take blood samples from local populations to determine if they carry a virus of animal origin. In the meantime, the project includes visits to these rural communities and interviews on social and environmental themes, against the backdrop of the extension of agricultural and tourist areas. “We cannot arrive and impose ourselves, we need an exchange of knowledge with the communities”, explains Erika Marcé Santos, of the NGO Kalaankab.