Great East. Covid-19, smallpox, rabies, Lyme disease… We tell you all about zoonoses

The bank rat is responsible, in Grand Est, for the transmission of a zoonosis. (©CC BY SA Wikimedia Commons)

The pandemic crisis Covid-19 illustrates the major impacts that the emergence of new living organisms responsible for diseases can have, especially zoonosesin our society, at the health, economic and social levels.

But it also raises many questions about its origin, its dynamics and the mechanisms that explain it. What are the links between damage to biodiversity, ecosystems and zoonoses? How to avoid them? And what is hidden behind the word “zoonosis”? Which are found in Lorraine, and in the Grand Orient ?

Explanations with Élodie Monchatre-Leroy, Director of the Rabies and Wildlife Laboratory at Nancy (Meurthe-et-Moselle)veterinarian and university doctor in microbiology-epidemiology.

What is a zoonosis?

A zoonosis is a disease that is transmitted from animal to human, or from human to animal.

Zoonoses can be “subdivided into two parts: vectorized diseases, that is, transmitted by everything that is tick, mosquito, etc. And those that are transmitted directly, without a vector”, defines Dr. Élodie Monchatre-Leroy.

What zoonoses are found in the region?

The Grand Est region is not spared by the presence of zoonoses. In addition to Covid-19 and smallpox, pandemics, we asked Élodie Monchatre-Leroy about those present in the region.

  • Puumala virus, transmitted by the bank rat

With 321 cases humans in France in 2021, this virus, from the hantavirus family, historically present in the Grand Est, has a variable incidence depending on the year. Its bearer is the bank rat.

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The last human case of terrestrial rabies in France dates from 2017. The contamination occurred in Sri Lanka. For animal cases, the last 2 date from 2020: a diagnosed dog raging on the Ile de Ré in February. The dog had been recovered in Spain and certainly arrived from North Africa, as evidenced by the rabies strain. the 2and case is a infected cat in May at the Grand Est, eating a bat.

  • Alveolar echinococcosis, transmitted by fox droppings

The disease, caused by the parasite Echinococcus multilocularisis transmitted with the berry contamination by fox droppings. Between 10 and 42 cases are identified per year (in data since 2008). Annual fluctuations are also due to screening.

For Lyme disease, better known and transmitted by ticks, a clear increase is notable across France: in 2009, 80 cases reported and 29,000 estimated, and in 2020, 347 cases reported and 60,000 estimated. Here it is also important to note the influence of improved screening over the years.

  • tick-borne encephalitis

Also transmitted (quite logically) by ticks, this disease requires – for the tick to become a carrier – that two individuals feed on the same host at the same time.

For this, the data are more fragmented, the disease is only notifiable since 2020. However, most infections, ie 88% (62/73), were acquired in Alsace. In 2020, a cluster of more than forty cases linked to the consumption of raw goat’s milk cheese was discovered.

However, these pathologies transmissible to human beings undergo transformations and tend to multiply.

Human activities, climate, extinction… What influences the increase in zoonoses

In essence, a zoonosis, vectorized or not, depends on its carrier – which is often healthy to vectorized, that is, asymptomatic.

However, “anything that can disturb wildlife can cause it to move, which increases the likelihood of contact between wild animals and humans,” explains Nancy, director of the ANSES rabies and wildlife laboratory.

Climate change is one of them. It disrupts the population dynamics of wild animals that can flee from floods, as has been observed with hantaviruses (such as the infections that occurred in the United States after a remarkable number of mice took refuge in dwellings), or animals in search of water due to the droughts that also lead to lack of vegetation.

Elodie Monchatre-LeroyVeterinarian and Director of the Nancy Rabies and Wildlife Laboratory

However, this change can also lead to a decrease in the possibility of reproduction of certain species and, in fact, to the reduction or even elimination of a certain population (eg rodents).

“Human activities play into the climatethat influences biodiversity which, when disturbed, has an impact on the transmission of zoonotic agents”, he describes, highlighting the multifactorial aspect of the influences on their number and propagation.

Are zoonoses becoming more numerous?

Yup. And the vet logically explains:

There are more and more human beings on the Earth’s surface, which inevitably increases the contact surface between us and animals, and increases deforestation, thus disturbing the biotope of the fauna included. In addition, to feed the population, there are also more and more farms that can serve as amplifiers for emerging zoonoses.

Elodie Monchatre-LeroyVeterinarian and director of the ANSES rabies and wildlife laboratory in Nancy

In short, the probability of catching a zoonotic virus increases.

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