In the first half of the 20th century, researchers throughout the world confirmed the transmission of pathogenic agents by ticks . It was the discovery of Lyme disease in the late 1970s that rekindled their interest in ticks as vectors .
Bacterial infections
All the bacterial infections described here can be treated effectively with antibiotics, but only early diagnosis can prevent sequelae. Moreover, they do not lead to immunity: it is therefore possible to contract the same disease several times.
Lyme borreliosis
It is the most important human disease in the northern hemisphere and the bacteria responsible for it are the Borrelia , transmitted by ticks Ixodes . Depending on the geographical areas, when the bacterium is present, the infection rate generally varies between 2% and 20% in Europe, up to 50% in. Certain regions of the United States.
In the Overseas Territories, Lyme borreliosis is currently non-existent. In France, the risk of contracting the disease is greatest during the period of activity of Ixodes ricinus in spring and autumn.
Recurrent fevers Borrelia
Other Borreliae can affect humans and are responsible for recurrent fevers. They differ from the previous ones in that they cause a high fever.
They are found mainly in tropical areas, where they are often confused with malaria, but also in the United States. They are mainly transmitted by soft ticks of the genus Ornithodoros , which bite at night.
Read also: The tick bite
Anaplasmosis
They are transmitted by bacteria Anaplasma . They mainly affect animals, but also humans. In this one, they are manifested by a flu-like syndrome, with fever and chills, malaise sometimes accompanied by digestive signs and rash skin.
Rickettsioses
The culprits are bacteria Rickettsia , transmitted during the bite, but also by skin wounds or by the eyes when they are rubbed with dirty fingers.
Tularemia
Tularemia is mainly present in the northern hemisphere. The bacterium is capable of infecting a very wide variety of animal species.
In humans, in Europe, the disease occurs either in winter during hunting, or in spring when tick activity peaks. The symptoms are an undulating and brutal fever, often associated with gastrointestinal manifestations.
Q fever
Around 40 species of ticks are capable of transmitting it, but the main route of infection is the inhalation of infected aerosols or dust from sick animals.
In humans, the disease is mainly manifested by a flu-like syndrome, atypical pneumonia and biological hepatitis. One in two individuals does not develop symptoms.
In animals, the bacterium could be responsible for abortions and could be associated with respiratory disorders.
cat scratch disease
Its main vector is the flea, but transmission by ticks Ixodes , although probably marginal, has been demonstrated.
The cat is generally not very sick, but it can present small haemorrhages. In addition to the possible transmission by tick bites, it is through its dirty claws that the cat transmits the bacteria directly to humans during scratches.
In humans, between one and three weeks after infection, the first symptomatic manifestation of the disease is the appearance of lymph nodes.
Cat-scratch disease is generally mild and has no sequelae, but in some cases the clinical manifestations may resemble eye infections, muscle pain or even neurological and cardiac damage, especially in immunocompromised patients.
viral infections
Tick-borne encephalitis (TBE)
TBE infections are today the most important vector-borne neuroinvasive disease in Europe and Asia. There are several thousand human cases per year.
The virus is transmitted to humans through tick bites Ixodes or ingestion of raw dairy products from infected animals.
The infection may be asymptomatic, but after incubation (one to two weeks), the disease manifests in two phases:
- a flu-like illness for two to four days;
- disappearance of symptoms for a week;
- a second febrile phase with neurological signs of varying severity.
Mortality is between 0.5% and 3% for the European and Siberian subtypes, but reaches 35% for the Far Eastern subtype.
France remains little affected to date, but an increase in cases has been observed in Alsace.
There is an effective vaccine against this infection, but no specific treatment.
Crimean-Congo fever
The virus is found in several countries in Africa, Asia, the Balkans, and the Middle East; he is absent from the new world.
The ticks of the genus Hyalomma are the main vectors as well as some Dermacentor and Rhipicephalus .
Among its hosts (hares, hedgehogs, rodents, domestic cattle, etc.), humans are the only ones to develop the disease. Migratory birds from Africa play an important role in the circulation of the virus and in the importation of infected ticks.
Crimean-Congo hemorrhagic fever is characterized by summer outbreaks in humans, which allow the identification of foci. It can be deadly.
Vector species are present in the south of France and in Corsica, but no case has yet been reported in France.
Parasitic infections
Babesiosis
They are also called piroplasmoses because of the pear-shaped parasite in red blood cells.
The disease resembles malaria, but it is a tick that transmits the parasite. Of more than a hundred species of Babesia only five species infect humans. Babesiosis is above all a veterinary problem, the economic impact of which is very significant.
In humans, its manifestations depend on the immune status of the patient. It is usually asymptomatic in people immunocompetent , but severe in debilitated individuals. The infection can cause anorexia, fatigue, fever, and blood problems.
In dogs, similar symptoms are observed. For animals, there is an antiparasitic treatment and several vaccines of varying effectiveness.
Theileriosis
The impact of these is essentially veterinary: Parasites infect both wild and domestic ruminants. They are transmitted by different Hyalomma, Dermacentor, Haemaphysalis, Rhipicephalus and Amblyoma.
The disease is most prevalent in tropical areas with a few cases in southern Europe.