Global warming could make ticks attack humans more often than dogs

(ORDO NEWS) — A further rise in temperatures on Earth will lead to the fact that ticks infecting dogs will be about two to three times more likely to settle on the body of the owners of four-legged pets than today. This was announced on Monday by the press service of the American Society for Tropical Medicine and Hygiene (ASTMH).

“Our observations show that rickettsia ticks are about 2.5 times more likely to bite humans than dogs if temperatures rise from 23 to 37 degrees Celsius. This means that the number of cases of the disease could skyrocket in the next years during heat waves and hot weather, “said Laura Backus, a veterinarian at the University of California, Davis, USA, quoted by ASTMH Press Office.

In fact, all climatologists on Earth today have no doubt that global warming exists and that it will radically change the face of the planet if the rise in temperatures cannot be contained at around 1.5 degrees Celsius. This is evidenced not only by hundreds of computer models of the planet’s climate, but also by thousands of measurements obtained using various climatic satellites, land-based meteorological stations and oceanic buoys.

One of the consequences of this process, as scientists found out at the beginning of the last decade, will be an increase in the number of parasites that infect both humans and various animals. For example, back in 2013, ecologists recorded a sharp increase in the number of ticks in Russian forests, and oceanologists and paleontologists found hints that an increase in sea temperatures would dramatically increase the number of parasitic worms in fish and other ocean fauna.

Backus and her colleagues discovered another example of how global warming can affect the behavior and prevalence of parasites by watching how air temperatures affect the behavior of brown dog ticks, one of the most common bloodsucking parasites in pets.

Climate and parasites
Under normal conditions, as the veterinarian notes, these ticks rarely attack humans, but in recent years, scientists have begun to assume that this has begun to happen much more often. The fact is that arthropod parasites spread rickettsia, the causative agent of Rocky Mountain spotted fever, the number of cases of which has grown dozens of times over the past twenty years.

Suggesting that the increase in the incidence may be associated with an increase in tick attacks and rising temperatures, the scientists tested how unusually high air temperatures could affect the behavior of these creatures. For these experiments, Backus and her team built a special cage connected by air ducts to two rooms where a man and a dog were.

By raising or lowering the temperatures inside it, biologists monitored how ticks behave in such an environment and whose scent would attract them more. These experiments showed that the preferences of the parasites were indeed highly dependent on the ambient temperature. For example, at 23 degrees of heat in the room, ticks almost always crawled towards the room with the dog.

On the other hand, in a very hot summer day with a temperature of 37 degrees Celsius, all tick subspecies changed their minds and tried to attack a person 2-3 times more often than their traditional prey. In the case of some tropical subspecies of brown dog ticks, this led to the fact that they began to attack exclusively humans, while other parasites simply lost interest in dogs, moving equally actively towards humans and towards the four-legged pet.

Both, scientists believe, explain why the incidence of Rocky Mountain spotted fever has increased dramatically in recent years. This should be taken into account when preventing diseases spread by blood-sucking invertebrates, including other types of ixodid ticks, summed up Backus and her colleagues.


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