Pick, shovel and canary. For centuries, workers descended into coal mines with a canary in a cage. This animal, being smaller, suffered the effects of toxic gases before humans, so its condition could serve as an alarm in the event of a gas leak. More than a canary, he was a sentinel. A similar approach is proposed by an editorial published in the magazine Sciencea showcase of the best world science, which suggests that dogs should become the guardians of human health. Because they share the same environment as their owners, dogs can help study, for example, the epidemiology of vector-borne pathogens, the effects of exposure to heavy metals or microplastics, and even the effects of social difficulties, the authors argue.
“Dogs are special animals because they have coexisted with humans for about 30,000 years. By sharing space, the factors that can influence their health are very similar to ours,” explains Courtney L. Sexton, professor at the University of Virginia and co-author of the essay (with Audrey Ruple). In addition, the way in which dogs move around the world means that they have a higher incidence of infectious diseases. They suck everything they find, they spend more time in areas populated by disease vectors – such as in a meadow full of ticks – and they do not have hygienic habits. Finally, they live much shorter lives than humans, so “we are often able to make connections between environmental impact and life outcomes more quickly in them,” Sexton explains.
There have already been some isolated examples of sentinel dogs. 2007, in the United Statesan increase in kidney failure in pets led to the investigation and subsequent withdrawal of a contaminated feed. This feed was also used as food for chickens and pigs intended for human consumption and was quickly withdrawn, avoiding possible consequences for the local population. The idea, according to the authors, would be to turn this case, the exception, into something more like the rule. And for this, canine data collection would have to be improved, with a sentinel program in veterinary clinics. “This would help evaluate the health of the people who cohabit with them,” the researchers state in their article.
The context is favorable due to the way in which our relationship with pets has evolved. “On the one hand, we have improved a lot in veterinary medicine, there are more analytical techniques,” he says. Guadalupe Miro, Professor of Parasitology and Parasitic Diseases at the Complutense University of Madrid. Animals are much more controlled today than a few years ago and it would be easier to find spikes in certain diseases.
“On the other hand, direct contact habits have become much more relaxed. Dogs used to be working animals and contact with them was less common. Now it seems funny that a dog licks your face and many people share their bed with them. You have to understand that you have to take care of your hygiene habits,” Miró laments. This makes it easier for diseases to jump from one species to another. Dogs and people do not share many diseases, but they do share vectors such as ticks, certain infections and also some diseases of parasitic origin, such as leishmaniasis.
Dogs or cats?
The writing of Science emphasizes the concept of one health. “It’s a transdisciplinary approach to public health that is based on the principle that the health of people, the environment and the other animals that we share our environment with are interconnected,” explains Sexton, who clarifies that although the underlying concepts are not new, there has been a renewed recognition of this idea in the last 20 or 30 years.
Miró exemplifies this idea of a single health by referring to a case in which he personally worked: the outbreak in Fuenlabrada. “It was an outbreak of leishmaniasis that arose in the Community of Madrid in 2010. Suddenly there was a boom of cases in nearby hospitals in the south of Madrid.” The first thing they thought was that the disease could have jumped from dogs to people, but when they sampled the dogs in the area they saw that there had been no rebound in this disease. Then the experts looked at a newly created park. “In the Polvoranca park there was a huge population of hares, because they didn’t have any predators there. And it was seen that the vectors fed on the hares, they actively multiplied and began to infect people who went to the parks for a walk.” In this way, the circle was closed and it was demonstrated that human health is closely related to that of the animals with which it lives and the environment in which it moves.
In a response editorial published also in ScienceRamiro Pastorinho, a researcher at the Department of Medical and Health Sciences at the University of Évora (Portugal), says that the present study “highlights the not-so-obvious role that companion animals can play as sentinels of public health, social well-being and human health.” Pastorinho praises the study’s vision, but qualifies some of its proposals. “The belief that, among companion animals, dogs are the best placed to be sentinels is debatable,” he says. “For example, cats, due to their grooming habits, similar to children’s hand-to-mouth behaviour, are much better sentinels of exposure for young children.”
Turning dogs or cats into sentinels of our health has the same advantages. And above all, the same limitations. The veterinary network does not have a sentinel program or a centralized system. It is difficult to add up isolated cases to find a trend. It is difficult to understand the health of pets in a global way. But as this article warns, it is important to change this mentality; collecting data more efficiently can not only improve the health of pets. It will also do the same for that of their owners.
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