Improving knowledge and fighting tick-borne pathogens
Updated on 05/08/2016
Ticks, Lyme disease, Zoonosis
Ticks, along with mites, belong to the subclass Acari, and are found mainly in wooded areas in the spring and summer. In Europe, they are the most common vectors of infectious diseases in humans and animals. They can transmit bacteria, viruses and parasites. In France, the main disease transmitted to humans by ticks is Lyme disease. ANSES studies tick-borne pathogenic agents in order to identify and characterise them and more effectively combat them.
Ticks (Ixodes ricinus) belong to the Acari subclass, and are found in wooded areas in the spring and autumn. They are responsible for vector transmission of infectious diseases that can affect animals and humans (zoonotic agents). Ticks are the most common vectors of infectious diseases in Europe.
There are just under 1000 species of tick in the world, but only a few are carriers of disease (mild to severe).
These diseases can be caused by:
bacteria (Lyme disease, rickettsiosis, tularemia, bartonellosis),
viruses (tick-borne encephalitis, tick and haemorrhagic fevers, louping-ill in sheep),
parasites (canine piroplasmosis, bovine babesiosis).
How do ticks transmit diseases?
Ticks feed on the blood of the human or animal hosts to which they attach themselves and may become infected by pathogens from infected hosts. They can then retransmit the pathogens to new hosts whose blood they feed on. Ticks are therefore known as disease "vectors". Diseases are mainly transmitted through their saliva.
Ticks are excellent vectors because:
The feed on large quantities of blood for long periods (and therefore have a higher chance of absorbing a pathogen).
Attached to their host, ticks can travel long distances (high dissemination capacity).
Thanks to their relatively long lifespans (several months), pathogens are kept alive in nature for prolonged periods.
They feed on a wide variety of hosts that can be carriers of many different pathogens.
They reproduce in large numbers.
Additionally, tick bites are painless.
Lyme disease, the main disease transmitted to humans
In France, the main disease transmitted to humans by ticks is Lyme disease. It is caused by a bacteria belonging to the group B. burgdorferi sensu lato, which comprises at least five species pathogenic to humans which are found in France.
Several days after a tick bite, erythema migrans (a typical red "bull's eye" rash pattern) appears, spreading outward from the central bite location. At this stage, an antibiotic treatment can effectively treat the disease. However, without treatment the disease can cause cutaneous, muscular, neurological and articular damage that may be highly disabling.
Antibiotic treatments exist which are effective if administered rapidly. It is therefore important to obtain a prompt diagnosis following a tick bite.
To protect yourself from tick bites when taking walks in wooded areas:
wear clothes that cover the body
inspect your body after walks
immediately detach attached ticks using a tick remover, thin tweezers, or your fingernails (never use ether or similar products)
disinfect the wound
If an erythema migrans rash should appear following a tick bite, see your doctor immediately.
The work of the Agency
Via its Maisons-Alfort Laboratory for Animal Health, ANSES studies tick-borne pathogens. To do this, it organises regular tick collection campaigns in various regions of France. The pathogens found in the ticks are then identified using high throughput techniques.
The ticks' competence in transmitting the newly identified pathogens is studied and the laboratory develops innovative methods for providing epidemiological surveillance of these pathogens. In this way, ANSES can better understand the pathogens transmitted by ticks in order to more effectively combat them.
This research topic, at the interface between animal health and human health, shows how the fight against animal-borne infectious diseases is consistent with the "One Health" concept implemented by the international health authorities.
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