West Nile, dengue, Lyme disease, leishmaniasis. What do they have in common? They are all zoonoses or inverse zoonoses, now known and sadly topical terms. The first and most frequent case, namely that of diseases that are transmitted from animals to humans, was the subject of a symposium at the congress of the Italian Society of Parasitology (SoIPa), organized by Msd Animal Health.
The starting point is there One Health, a concept that expresses the interconnection between human beings, animals and the environment: when a health problem emerges for one, all the others can be and indeed are always involved. According to EFSA (European Food Safety Authority), 75% of the diseases that have affected humans in the last 10 years have been transmitted by animals or products of animal origin.
We already know about leishmaniasis, dengue, the current spread of Lyme disease on the rise due to the proliferation of ticks, and West Nile fever, caused by the virus of the same name, whose reservoir are birds and mosquitoes that transmit it to humans. with their stings.
But there is an important distinction to be made: “Let’s talk about perfect spillover when the virus passes to humans but does not stop and is capable of being transmitted to other people, as happened with Covid – explains the doctor Joy Hair, of the National Reference Center for diseases in the human / animal / environment interface of the IZS Venezie. In classical zoonoses, such as West Nile, we are accidental guests but we do not pass the virus to other human beings, except through medical practices such as transfusions “.
The transition from animal to man
But what are the social and environmental conditions that favor the passage to man? “All those that influence or favor the encounter between man and wild animal” adds the doctor. There are particular environmental, climatic or social conditions that lead to an increase in wild animal-human contact. “Climate change can affect, for example, the movements of animals that no longer find a suitable habitat for their survival and approach humans. The variations in heat and cold, humidity affect density and movements. Then there are the upheavals caused by wars: the fright of animals leads them to travel that they would never have done “.
When man enters their habitat
Then there are the cases in which it is man who enters the habitats of wild animals. “This is the case, for example, of speleologists, of those who research bats in the caves, but also of those who go into the woods in search of a bit of coolness and come into contact with ticks. An encounter that can end with a classic zoonosis , which however remains unusual “.
The first step for the citizen is to establish a correct relationship between humans and animals. “The wild must be treated with respect and must continue to live far from man, in their habitats, which should be guaranteed and protected”. If we are “forced” to invade their space, we must know how to behave, avoiding disturbing them.
“From the scientific point of view, however, we must start with knowledge, to discover which pathogens are found in these animals, in avian fauna, in pig farms – continues Dr. Capelli. Now we have all the tools to do this, genetic methods that highlight pathogens we do not even know existed, genetic sequences (next generation sequency) that allow you to explore all the microorganisms that live in an animal. There is the whole world. “And this is the first step.
And then the surveillance
The second step is surveillance. “Once we have identified zoonotic pathogens, we can keep them under control, monitoring mutations. When a virus can infect a mammalian cell, we realize it with the genetic sequence, and we can keep the basic elements ready to create, in case of need, a vaccine “.
The Italian integrated plan, unique in Europe
And in this Italy can boast a unique plan in Europe. “Let’s start from the fact that we have veterinary medicine under the ministry of health, while in all other countries it is under the ministry of agriculture”, continues Dr. Capelli. “But when there are zoonoses, different plans cannot be made for humans, animals and the environment, but an integrated plan must be created, where all the veterinary part works at the service of human health, as happens in our National Arbovirus Response Planunique in Europe “.
The West Nile case
The doctor then brings a practical example, relating to West Nile, which unfortunately passes from man to man through blood donations. For this reason, all donors must be checked even if asymptomatic, with an enormous cost in economic terms. “Before the virus circulates in humans, we can detect it in mosquitoes. So the blood centers remain stationary until they receive the ok from veterinary medicine. From May to November the situation is monitored through traps placed in geographical units, check weekly “. So you can more easily know if the virus is there and how widespread it is, by checking its vector at a much lower cost. “Here it means integrated system, it makes no sense without talking to each other”. And this is also there One Healththe unique health, the one that connects man, animal, environment and acts in unison for the protection of all.