Ticks hardly know borders. This is what a study published on Monday, November 18 in the journal Frontiers in cellular and inspection microbiology. These mites, which feed on blood, have a privileged means of transportation: migratory birds. Clinging to their host, they travel thousands of miles, far beyond their usual ranges. And with global warming, more survive in their destination, as do the pathogens they carry.
To study this phenomenon, American researchers set up bird traps along the coast of the Gulf of Mexico. Once captured, the birds were identified and examined to determine if they were carrying ticks. The scientists then mapped the geographical distribution of the migrants to understand where they might have contracted these parasites.
“The results showed that ticks could be transported to distances of up to 5,000 kilometers.”explains Shahid Karim, from the University of Southern Mississippi and lead author of the study. This shows that ticks are now reaching areas where they could never have established themselves before. The increase in temperatures linked to climate change provides them with favorable conditions for their establishment and propagation. »
Lyme borreliosis, the most common disease
A worrying situation, when we know that ticks are excellent vectors of pathogens, responsible for diseases in animals and humans.
The most common tick disease is Lyme borreliosis, caused by the bacteria Borrelia burgdorferi sensu lato It is transmitted to humans through the bites of infected hard ticks of the genus Ixodes. According to the study, in the United States more than 95% of vector-borne diseases are related to these parasites. “Not only could these ticks bring new pathogens, but if they manage to establish themselves in the United States, they could become additional vectors for pathogens already present in this country and transmit them to wildlife and humans”explains Shahid Karim.
In total, the researchers collected 421 ticks from 164 birds, a number “not inconsiderable” according to Pasteur Institute arthropod researcher Sarah Bonnet: “Four hundred is enough for a population to establish itself. A female tick can lay thousands of eggs at a time. So, if all conditions are met, a single fertilized tick can allow the establishment of a new species. »
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