Colds, coughs, parasites, lice… Humans and animals can contract similar diseases that have similar characteristics without being transmitted from one to the other. If humans and dogs can both have lice, for example, they are two different species of parasites, which is why contamination between the two is not possible. The same goes for the common cold between humans and cats, which are two very distinct viruses that cannot be transmitted between the two species.
However, there are many diseases that are transmitted between humans and animals, which are called zoonoses. If we most often mention those that animals can transmit to us, you should know that there are some rare diseases that humans can catch before contaminating their dog or cat.
Zoonoses: the diseases we share with our animals
We speak of zoonosis to refer to any disease or infection that is transmitted between vertebrate animals and humans or between humans and vertebrate animals. Science is primarily interested in the pathologies that they can transmit to us, for public health reasons. Indeed, very few studies are carried out on those that we are likely to convey to them. They are few, in fact, but do exist and they all require as many precautions, for obvious reasons of more extensive risks of transmission. In addition, it can be worrying for a sick master to know if he can transmit his virus to his little companion, cat or dog.
The diseases that humans and animals “share” are recognized and have existed for millennia. Their origin dates back to the domestication of animals and their breeding, which greatly contributed to the proximity of species and the sharing of bacteria, viruses and other microorganisms.
The epidemics that have spread over the centuries are above all the result of a lack of hygiene and/or health safety. Man’s responsibility is complete. The destruction of wild life spaces promotes inter-species contacts that have never occurred and/or that upset the fragile balances put in place by nature. By increasingly colonizing ecosystems, destroying wildlife and reducing the natural borders formed between humans and certain animal species, the transmission of viruses and diseases is more important. Like a border that is no longer guarded, exchanges take place, except that these sometimes have disastrous consequences for the natural balance and the health of humans and animals alike.
If animals are often incriminated and if humans delight in making them responsible for a good number of diseases, it is largely because of their anthropocentric vision – as evidenced by the very rare studies that focus on diseases. transmitted by humans to animals in comparison to many relating to reverse contamination – but not only. To consider that Man has his share of responsibility, we must go back very far to the origin of viruses.
For example, the Mycobacterium bovis, which is the agent of bovine tuberculosis, has for ancestor an agent that humans transmitted to bovines. Indeed, the disease has been identified in particular on the skeleton of an Australopithecus dating back more than 2 million years.
The transmission of inter-species diseases: when humans infect animals
Man carries bacteria within him and he is in regular contact with viruses which are part of his daily life. Over the course of evolutions and generations, the body develops defense mechanisms that make it possible to fight against these invasives or to “live with them”, that is to say with a reasonable level of risk to health.
However, these bacteria and viruses can present another form of danger to the health of other animal species. The rare scientific studies carried out on the subject have in fact shown that many of the diseases that animals know today and that they are likely to transmit to us have their origin in… humans! Humans have probably contributed to the decimation of certain animal species in a localized way, in particular groups of monkeys.
To understand this transmission and the place of the evolution of a species within its environment, it is also possible to evoke contamination between humans. Indeed, some populations accustomed to living in more remote areas have been seriously affected by viruses and bacteria from other populations. If the first European colonizers brought diseases to the New Continent which decimated many indigenous peoples several centuries ago, certain populations living in the Amazon, in areas far from other civilizations, are still, today, susceptible to perish in contact with benign pathologies for the foreigners that we are, and vice versa probably. Survival within an environment pushes humans and animals to evolve in such a way as to resist the dangers that are likely to eradicate it.
Several transmissions from humans to animals have been clearly identified. This is the case of respiratory diseases observed in chimpanzees and transmitted by humans. The latter can also transmit hepatitis A to the monkey. Humans and pigs also share a great genetic proximity, which is why certain diseases pass from one species to another and favor inter-species contamination, like certain influenza viruses. Influenza, including the H1N1 flu. The ferret, which is now a domestic animal, can catch the flu from humans and pass it on to him.
Unfortunately, human pollution favors the contamination of wild species. Indeed, humans massively diffuse antibiotics in the environment and contribute to reduce the immune resistance of many species, thus leading to an easier circulation of bacteria and viruses.
By dint of destroying his environment and the natural balance of ecosystems, man is destroying himself.
Can humans contaminate their dog or cat?
Closer to home, many dog and cat owners are wondering about the risk of contamination of their little companions when they themselves are sick. I have the flu, can my cat catch it? I have lice or chiggers, can I transmit them to my doggie? Normal and legitimate questions.
Fortunately, most diseases that seem similar to us cannot be transmitted from humans to animals. As an owner, you are more likely to catch a disease brought by your cat or your dog than to transmit one to him. The human cold, for example, is unique to humans. The one that your little companion may present is not of the same nature. The lice that your children may bring home from school are not likely to parasitize your animal, because those that invade humans, cats and dogs are completely different species.
Nevertheless, we know that certain human diseases can affect our little companions. Science, as we have said, pays little attention to the transmission of viruses in the human-animal direction and insists that the majority of viral strains that impact humans do not affect our pets. However, in 2009, a case of contamination of a cat by influenza A H1N1 was identified in France. It was unfortunately not isolated, other small felines having been affected around the world. In France alone, thirteen cats and one dog were infected with the same virus between 2011 and 2012, infections transmitted by humans.
What are the main diseases that pets can transmit to us?
The risk of contamination is greater from animals to humans. Indeed, our dogs and cats are likely to transmit several pathologies to us.
- Rabies : pets are vectors of rabies, which is why it is recommended to have them vaccinated. They are themselves contaminated by carrier animals, such as foxes, raccoons, skunks or bats, but also other affected dogs and cats.
- Toxoplasmosis : this parasite can be transmitted to humans by the cat, itself infected by the mice that it hunts and ingests. Toxoplasmosis is mainly transmitted through the cat’s stool. It presents a significant gravity for pregnant women who can have a miscarriage in contact with the parasite brought by the kitty.
- Ringworm : this fungus, ringworm, which develops on the skin of cats can be transmitted to humans, but the case is mainly observed in allergic or immunodeficient people.
- intestinal parasites : more than 55 parasitic zoonoses have been identified. It is important to deworm your little companion regularly to avoid contamination.
- salmonellosis : dogs infected with the bacteria Salmonella can transmit it to humans through their excrement.
- Leptospirosis : Dogs who drink dirty water in ponds or swamps can develop this disease which lodges in the kidneys and urine. It is very dangerous for humans, but a vaccine exists to limit its effects in animals.
