Like any living being, a tick spends most of its life seeking food and reproduction. It is during its meals that it will, if necessary, take an infectious agent from a host. Then she can pass it on to the next ones.
The tick-biting device
Once it has set its sights on a host, the tick anchors itself in the latter's skin. From then on, she does not let go of him again before the end of her blood meal.
The mouthparts of ticks are composed of two chelicerae and a hypostome. They are impressive when viewed under a microscope. The chelicerae are like saws, capable of dilacerating the tissues. The hypostome, armed with rows of teeth, functions like a harpoon which anchors itself very firmly in the host. The whole constitutes the rostrum. Many species also synthesize a kind of glue, cement, which reinforces their attachment.
This is what makes the extraction of the tick hazardous. It is especially important to avoid pulling brutally on a fixed tick, under penalty of breaking the biting parts.
During its blood meal, the tick absorbs the blood of the host while injecting it with saliva. The particular substances that make up the tick's saliva destroy the tissues and dilate the vessels. In addition, they prevent blood clotting. Thus, the rostrum can easily penetrate the skin where it clings firmly with the help of its harpoons.
These substances also have the property of inhibiting pain and itching. This explains why in most people bitten, the bite goes unnoticed . In addition, tick saliva also contains factors that inhibit the host's immune system.
Following the bite, the subject risks a skin reaction or an infection, if the tick is infected. In this case, the risk of developing a disease increases as time passes .
The tick bite
Even in the absence of transmission of infectious agents, ticks can create problems by the simple fact of their bite. They are manifested by reactions to saliva, significant blood loss or superinfection of the wound.
Saliva allergy can be more or less serious, from a harmless skin reaction to a life-threatening anaphylactic shock . Soft tick bites of the genus Argas can cause extreme reactions of this type in some people.
A new allergic phenomenon has recently been described following stings. This is an allergy to a sugar called “alpha-galactose” or “alpha-gal”. This one is contained in the saliva of the tick but that the human being does not synthesize. If the bitten person then eats red meat that contains this sugar, anaphylactic shock may occur. Initially described in Australia, this phenomenon is becoming increasingly concerning in the United States. A few cases have also been reported in Europe.Ticks, Lyme & Cie , Sarah Bonnet & Nathalie Boulanger, Scitep Editions 2019
The saliva of some hard ticks can cause a paralysis known as ascending tick paralysis . This can occur following a puncture near a nerve path in sensitive people or animals. Paralysis, progressive, can lead to death.
This problem, which concerns animals, is the most well-known direct effect. A massive infestation may correspond to the collection of considerable quantities of blood. As a result, it can lead to anemia in the animals concerned.
Significant economic losses related to the production of milk or meat may result.
Diseases caused by ticks
Most tick-borne diseases are described as emerging, otherwise appearing in an area where they did not exist, or increasing in a given place. They are practically all “zoonoses” whose agents are transmitted naturally from animals to humans, and vice versa . The infection can be of bacterial, viral or parasitic origin.