2023-05-24 09:10:01
In 2020, public health authorities estimate more than 60,000 cases of Lyme disease each year in France. But this borreliosis is not the only disease transmitted by ticks. At a time when outings in the forests, mountain hikes and nights camping are resuming, researchers are publishing a study on diseases transmitted by ticks, depending on the species of tick. Results.
Tick bites and Lyme disease
Every year, the tick bites are responsible for several thousand cases of Lyme disease, a pathology that can have serious consequences if not diagnosed and treated in time. By biting, the tick transmits bacteria to humans (among others of the genus Borrelia) that are responsible for the disease. But the situation is actually more complex. Indeed, there is not just one species of ticks, but several, just as there is not just one disease transmitted by ticks, but several.
In Marseille, there is a reference center, a world specialist in diseases transmitted by ticks. Researchers and doctors analyze ticks received from all over the world. In 2016, this team published a study on the different species of ticks taken from humans between 2002 and 2013, as well as the bacteria pathogenic to humans potentially transmitted when biting. The team has just published new data, on samples taken in France over the period 2014-2021.
Ticks, different species capable of biting humans
The researchers analyzed all the ticks taken from humans in France and sent to the reference center during the period under consideration. In total, the analyzes focused on 418 ticks, removed from 359 people. Various analyzes were carried out on these ticks:
- Morphological analyzes by an entomologist specializing in ticks;
- Spectrometric analyzes capable of differentiating ticks from other vectors of bacterial diseases;
- Genomic analyzes to identify bacteria transmitted by ticks.
At the same time, the clinical and demographic characteristics of bitten patients were taken into account. Serological analyzes were carried out to determine if these patients had been contaminated by a bacterium transmitted during the bite.
On all the ticks analyzed, the results highlight several species of ticks :
- Of the Ixodes (47% of ticks analyzed);
- Of the Dermacentor (33 %) ;
- Of the Rhipicephalus (16 %) ;
- Of the Hyalomma (3 %) ;
- Of the Amblyomma (2 %) ;
- Of the Argas (0.5 %) ;
- Of the Haemaphysalis (0.5 %).
Demonstration that ticks constitute a fairly diverse family!
More than half of ticks carry pathogenic bacteria!
In parallel with the different species of ticks found, the researchers detected that 58% of ticks carried at least one pathogenic bacterium. And the pathogenic bacteria vary according to the species of tick in question:
- Rickettsia is raoult et Rickettsia slovaca for ticks of the genus Dermacentor;
- Borrelia For ticks of the genus Ixodes;
- Rickettsia massilia for ticks of the genus Rhipicephalus.
What is the point of distinguishing tick species and the different pathogenic bacteria? When bitten, it is impossible to determine the responsible species with the naked eye.
Developing techniques to identify the species of tick in question and therefore to know which bacteria it can transmit is important to determine the best treatment for the patient. Of all the patients in the study, 107 presented symptoms following the bite and 26 of them developed an illness. Among the diseases observed were scalp sores, neck lymphadenopathy et Lyme disease. The implementation of a preventive antibiotic treatment following a bite can be oriented thanks to the results of this study. All cases of Lyme disease observed resulted from a bite by a single species of tick, Ixodes ricinus.
Estelle B., Doctor of Pharmacy
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#Tickborne #diseases