This visible sign generally appears within 30 days of the bite, sometimes later…
Around 50,000 cases of Lyme disease are recorded in France each year, according to Inrae. Mainly in the Grand Est, Burgundy-Franche-Comté, Auvergne Rhône-Alpes and Nouvelle Aquitaine. The disease is caused by the Borrelia bacteria, transmitted to humans by the bite of an infected tick. The tick transmits the disease at the larva, nymph and adult stages. 15% of ticks carry it. There are three stages of Lyme disease: early localized, early disseminated and late disseminated. The earlier it is diagnosed (at the early localized stage), the better because this allows antibiotic treatment to be started without delay. To do this, you must locate the bite – which is not always easy since the tick can bite in discreet places: behind the knee, the calf, the ear or under the armpit – and look at it carefully in order to find a particularly suggestive sign of an infection by the Borrelia bacteria.
This is the first visible sign of infection. It occurs within 30 days of the bite, sometimes “up to 3 months later“, explains Dr Alice Raffetin, coordinator of the Reference Center for Tick Vector Diseases, Paris and the Northern region. This sign takes the form of‘an oval or round spot that can expand centrifugally to reach up to 30 cm in diameter. This is called erythema migrans. This is a skin lesion that appears on the body at the site of the bite. “This lesion does not hurt, is not hot and does not itch so it can easily go unnoticed depending on its location. continues our interlocutor.
Erythema migrans is the most common manifestation (60 to 90% of cases) and the most suggestive of Lyme borreliosis. It should not be confused with a reaction to tick saliva which appears earlier and does not spread centrifugally (in a circle). When the erythema is not initially treated with antibiotics, the bacteria can migrate away from the bite: we then arrive at the “disseminated” stage. “Erythema migrans can become multiple. Spots then appear in several places on the body” explains Dr. Raffetin. This stage can occur several days to several weeks after the tick bite. In addition to spots in various places on the body, the patient may present neurological symptoms (facial paralysis, isolated meningitis), joint symptoms (arthritis with effusion of a large joint like the knee), cardiac or ophthalmological.
When returning from a walk in the forest, in a park or a picnic in the garden, meticulously observe all areas of the body, particularly folds and private parts, pass your hand over the skin to feel for any ticks attached, do not hesitate to get help for the hard-to-reach parts (back, neck, scalp) and repeat the same action the next day. If bitten, remove the tick with a tick remover and disinfect. Any other method for removing a tick should be avoided (oil, alcohol, ether, etc.).