Tick ​​bite

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In a tick bite (also tick bite ) is of a skin- tick with the jaw claws scribed and then (which is the "spine" hypostome ) in the wound anchored. The tick does not prick a vein, but tears a wound that runs full of blood from injured capillaries (so-called pool feeder ). Before starting to eat, the tick releases a salivary secretion that contains several important components.

  • An anticoagulant that prevents blockage of the proboscis (hypostome) and increases blood flow to the puncture site.
  • A type of glue that firmly anchors the mouthparts to the skin.
  • An anesthetic that makes the puncture site insensitive.
  • An anti-inflammatory agent that is supposed to avoid stimulating the body's own immune system at the puncture site.

Then the blood is absorbed by the tick. The upper side of the hypostome forms a recessed channel that forms a food channel with the lower side of the chelicerae. The mouth opening is above the hypostome, at its base. The underside of the hypostome bears rows of teeth that are shaped specifically for the species. The longer the tick species remains anchored in the host, the coarser these are.

infection risk

When sucking, the tick chokes or spits (regurgitates) back indigestible food residues into its host at regular intervals during the blood meal . In this process in particular, pathogens that have previously been ingested from a previous host and have maintained or even multiplied in the tick's body can be transferred to the next host. Pathogens that are found in an infected tick's intestinal tract are not necessarily transmitted to humans immediately, but sometimes only during the act of sucking after a few hours (in Lyme disease, for example, about 6 to 24 hours after the prick). It is therefore strongly advised to remove a tick as quickly and carefully as possible.

The stage of development of the tick also has an influence on the risk of infection. A tick in the nymph stage contains ten times more pathogens than an adult tick.

Transmitted Diseases

Warning of ticks in a forest area in Mecklenburg-Western Pomerania
Erythema migrans as an early manifestation of a tick bite with borreliosis infection (stage I) on a man's lower leg

The different tick families or genera can transmit the following pathogens or toxins (and diseases) to humans :

Leather ticks (Argasidae)

Shield ticks (ixodidae)

The most important vectors in Central Europe are the species of the genus Ixodes with the most common native species, the common wood tick ( Ixodes ricinus ), in the eastern USA Ixodes scapularis , in Russia Ixodes persulcatus . Other genera are Rhipicephalus , Dermacentor , Haemaphysalis , Amblyomma .

The saliva therefore also contains pathogens ( viruses , bacteria , single-cell or multicellular parasites ) that the tick ingested with the blood of an infected victim when it had previously eaten. If these pathogens not only survive in the tick, but also multiply or transform in it, the tick is a host or intermediate host for these pathogens and infects its next food victim in the manner already described. Ticks, including the common wood tick, which is most common in Central Europe, are found to be vectors , i.e. carriers of viruses ( arboviruses ) and bacteria. They can therefore transmit a wide variety of infectious diseases to humans and all possible vertebrate species through their sting . A purely mechanical transmission of viruses adhering to the lancing organ is also possible.

The following pathogens or diseases can be transmitted:

and around 50 other diseases worldwide such as Texas fever - the most important diseases are briefly presented below.

Lyme disease

→ Main article: Lyme disease

Borreliosis is the most common tick-borne disease in the northern hemisphere ; it is often associated with severe neuropathic symptoms and is triggered by the bacterium Borrelia burgdorferi from the group of spirochetes . Borrelia infection by ticks is possible throughout Germany, in the Swiss Central Plateau and in central and eastern Austria. Ticks are also found in cities: a study at the Max von Pettenkofer Institute for Hygiene and Microbiology ( LMU Munich ) showed that “direct contact with bushes in gardens is a previously underestimated risk” of contracting Lyme disease from a tick bite .

In 2004, the mean infection rate of ticks with Borrelia ( B. burgdorferi species) in southern Germany was 30%. The number of new infections per year for Germany is estimated at 50,000 to 100,000. There is no vaccination against Lyme disease, but it can be treated with antibiotics if it is detected early . In Germany, borreliosis is a reportable disease in the new federal states and Berlin .

Early summer meningoencephalitis

→ Main article: Early summer meningoencephalitis

Early summer meningoencephalitis (TBE) is also transmitted by ticks in Europe. It is caused by viruses and causes inflammation of the brain or meninges . The transmission of these viruses in the tick's saliva cells begins immediately after the bite and can increase significantly in the course of food intake until the viral load necessary for an infection with a subsequent outbreak of disease is reached . However, early summer meningoencephalitis is not limited to early summer, but ticks can also transmit the pathogen in late summer or autumn. The tick season is from March to October, but can be longer in mild weather.

A vaccination against the TBE is possible. In the German-speaking area, there is a risk of TBE infection only in certain areas, which, however, expand along the rivers from year to year. While it is otherwise assumed that every 20,000th tick carries the virus, 0.1–5% of ticks in these epidemic areas in Germany are affected. TBE is only actually transmitted in 30 percent of cases.

Q fever

The pathogen responsible for Q fever , the bacterium Coxiella burnetii , which causes this disease in particular in cattle, pigs, horses, sheep, goats, but also in wild animals and domestic animals such as deer, foxes, cats and dogs, especially in southern Germany, it is not primarily transmitted to humans by the spring forest tick ( Dermacentor marginatus ) from the sheep tick genus . Infection occurs when the tick first stings an infected animal and then a person. But it is enough to inhale the tick's droppings. Q fever is a reportable disease according to the Infection Protection Act.

Babesia

The marsh tick ( Dermacentor reticulatus ) from the kind of dermacentor is particularly lately in Germany with the holders of dogs and cats as carriers of the blood parasite Babesia ( Babesia canis canis feared). These unicellular organisms attack domestic animals and, like malaria, destroy red blood cells. Therefore, the most common symptom of babesiosis ( piroplasmosis ) is anemia . Further symptoms in the infected animals can be a high fever, red or greenish urine or jaundice. Some species of babesia are also transmitted to humans by the auzecke. However, these pathogens are not very dangerous for humans. Only in rare cases do they trigger flu-like symptoms if the immune system was previously weakened. The pathogen Babesia canis canis , which was first detected in the German state of Brandenburg in April 2005, only affects dogs or canine-like animals such as foxes after transmission by the auzecke. This pathogen is therefore strictly host-specific and can therefore not be transmitted to humans.

Most cases with the human pathogenic parasite Babesia microti come from the USA. In Germany, only test kits for the American Babesia microti pathogen are currently used. However, it is known that the Babesia divergens pathogen is mainly found in Europe. It would make sense to check to what extent the test kits used can detect infections caused by Babesia divergens . Babesia attacks the erythrocytes (red blood cells). The babesia invade the red blood cells, multiply and destroy the blood cells. In most cases, the infection is said to be symptom-free in people with a strong immune system (immunocompetent), but this primarily affects the American pathogen Babesia microti. The Babesia divergens pathogen found in Europe is more aggressive.

After an incubation period of 1 to 6 (12) weeks, symptoms such as nausea, loss of appetite and fatigue appear; After a few days, fever, muscle weakness, headache and arthralgia appear, as well as severe symptoms of exhaustion. This is followed by hemolytic anemia, hemoglobinuria (red colouration of the urine) lasting a few days or weeks. In extreme cases, it can lead to kidney failure and acute lung failure.

Therapy: quinine , clindamycin In the event of severe hemolysis and impending kidney failure, exchange transfusions may be necessary.

Tick ​​paralysis

Reactions to the nerve toxin secreted by ticks as an anticoagulant can in rare cases also lead to paralysis and death in humans . Tick ​​paralysis has not yet been observed in Europe.

More diseases

Another tick-borne disease that is widespread in the northern hemisphere is tularemia . Also the boutonneuse fever , the Omsk hemorrhagic fever , the Crimean-Congo hemorrhagic fever , which Kyasanur Forest Disease , the East African coast fever and various hemorrhagic fever , ehrlichiosis and rickettsial infections (eg, the Mediterranean spotted fever and mainly American on the continent, at the Tick ​​bite fevers ( found in the Mediterranean and Africa ) are transmitted by ticks. In the tropics , ticks are carriers of spot , relapse , Texas fever and also Babesia , a parasitic species of protozoa. Ticks transmit more than 50 other diseases worldwide.

In addition, there may be as yet unknown pathogens, as often none of the known pathogens could be identified in people who had a fever after a tick bite .

Allergic reaction

Before the tick picks up their food, they injected through their proboscis ( proboscis ) a glandular secretion (in general, saliva ) in their victim into it. For the immune system of the food victim, this saliva is a foreign body despite the anti-inflammatory agent it contains.

Prevention of a tick bite

Regularly carefully searching the body - especially with children who play outside during the day - is the safest way to avoid tick bites. Protection against tick bites is also provided by using defense sprays as a preventive measure and by wearing clothing that largely covers the body. It makes sense not to give the ticks a chance to crawl in and under clothing. If you work intensively in bushes and tall grass, you can spray both your skin and your clothing beforehand with commercially available defense sprays. Additional screening should always be carried out, as the sprays do not exclude the infestation, but can only reduce the probability of an infestation. In addition, one should avoid walking through tall grass, bushes and shrubs with light clothes on during the tick months. The ticks lurk for their nearest host, especially on slightly damp grass. Ticks withdraw in dry and hot weather.

distance

This medical tick tweezer opens when you press it and can be applied directly to the puncture site from above or from the side.
Tick ​​tongs (When the metal cylinder is pushed back, the jaws open enough to grip the tick.)
Tick ​​card with two different sized notches that can be pushed under the tick.
Remove the tick with thread

A tick that has become entrenched should be removed as soon as possible. Studies on mice and hamsters have shown that the risk of borreliosis infection and possibly also the risk of infection with early summer meningoencephalitis (TBE) increases many times over with the duration of the sucking act. Only one in 14 animals was infected if the tick was removed within 24 hours; on the other hand, 13 out of 14 animals were infected when the tick was able to suckle for 72 hours. It is assumed that these results can also be transferred to humans.

When removing, the tick should be squeezed as little as possible in order not to expose it to additional stress and the associated panic reactions. However, there are no studies that show an increased risk of Lyme disease infection when the tick is squeezed. A study with gerbils showed that squeezing saturated ticks does not increase the infection rate and that the probability of infection only correlates with the duration of the sucking act. The tick returns relatively large amounts of excess water to the host during the act of sucking. As a result, the tick maintains its internal osmotic balance and concentrates the amount of usable substances. Infection with Borrelia mainly occurs at this stage.

Removal tools

Various instruments are used to remove ticks:

  • The tick is grabbed as close as possible with tweezers and pulled out while gently turning or shaking it. Tweezers specially designed for this purpose are available under the name Tick ​​Tongs .
  • Tick ​​cards (sometimes equipped with a magnifying glass) have inclined incisions in the corners, the flanks of which are pushed under the tick. The tick jammed in this way can then be levered out with the card. This method depends on relatively free skin and can hardly be used in the fur of animals.
  • A tick hook is a slotted, curved rod that works similarly to a nail iron .
  • With a tick snare, a pen-like tool, ticks can be removed very easily, although the tick usually survives the removal. Pressing the spring piston opens a loop that is placed over the tick flush with the host's skin. If you let go of the plunger, the noose pulls itself back into the pen and grips the tick by its neck .
  • With a stable thread, a tightening loop in the form of a square knot can be placed around the tick and the tick pulled out.

Pull out or unscrew?

It is being discussed whether rotating the tick will aid the removal process.

  • The Bavarian State Office for Health points out that ticks anchor themselves in the skin by means of a salivary gland secretion ("cement substance") and that the mouthparts are equipped with strong barbs. As a result, larger parts of the mouthparts could tear off when turned and remain in the skin. It is better to grab the tick close to the skin and pull it straight out with a gentle pull. At most, a slight turning back and forth or a careful shaking could facilitate the removal. Under no circumstances should the tick be pulled jerkily, but rather lift the tick slightly and hold it with continued pull until it loosens by itself. This could take a minute, but ensure complete removal.
  • In another study on infected dogs, on the other hand, it was found that in the categories "Time required to remove", "Grasping the tick", "Required force" and "Condition of the mouthparts after removal", the twisting method using tick tongs or the so-called "tick." Twister ”was superior to pulling it straight out with tweezers or a tick card.

Incomplete removal

Sometimes parts of the mouthparts remain in the wound; after removing the tick, a small black point can be seen. (It is not the "head" as popularly claimed, since ticks belong to the genus of mites and do not have a head.) In any case, further irritation of the wound and the risk of inflammation must be avoided. In many cases, the tick remains are rejected by the body after a short time. The remains can also be removed with sterile tweezers, e.g. B. from a doctor .

Investigation for pathogens

Tick ​​bites should be documented with a date and a photo in order to have evidence of the time of infection in the event of illness. If you do not trust yourself to remove the tick yourself, a doctor or pharmacist should be consulted for professional removal.

It is possible to have the removed tick examined for Borrelia in a laboratory using a PCR examination (polymerase chain reaction, a form of DNA examination). The costs for the service not borne by the health insurance companies are between 10 and 100 euros, depending on the provider. Some state health offices offer such an examination at cost price, such as the state health office Baden-Württemberg in Stuttgart. If this test is negative, the likelihood of infection is very low. A positive evidence is only an indication of a possible infection. This test is not recommended by any professional society as the sole proof of a Borrelia infection and is not shown in any relevant guidelines.

Quick test kits for home use are also available in stores to determine whether a tick is a carrier of Borrelia. So far, no reliable statements or studies are available about the reliability of the tests.

Legal

In the case of civil servants, a tick bite can be recognized as an occupational accident if it occurs while on duty. However, it is a prerequisite that the date and location of the tick bite can be determined with sufficient accuracy.

therapy

Since no reliable evidence of disease is possible, especially in the early stages of many of the communicable diseases except for reddening, if unspecific flu-like symptoms or joint pain occur shortly after a tick bite, the question of weighing up the risks and side effects of a suspected, possibly superfluous antibiotic therapy arises and - if such a measure is not implemented, but also if such a measure is conceivably unsuccessful - the possible health, social and financial consequences of years of chronic suffering (which in extreme cases can lead to disability) on the other hand. The relatively safe therapeutic window of around four weeks from infection with Lyme borreliosis to the onset of stage II (pathogen spread and onset of systemic disease) must also be taken into account.

In the early stages of an infection, tetracyclines such as doxycycline are the drug of choice because of their cell penetration and their effectiveness against many bacterial pathogens transmitted by tick bites such as Borrelia, Rickettsia, Ehrlichia, Anaplasma and Babesia. Due to the long generation succession of Borrelia, the treatment must be carried out much longer than with many other pathogens.

literature

  • Hans-Peter Wirtz: Ticks as a disease carrier: what to do if you get a bite? In: Biology in Our Time. Volume 31, No. 4, 2001, pp. 229-238, ISSN  0045-205X .

Individual evidence

  1. ↑ Harald W. Krenn, Horst Aspöck: Form, function and evolution of the mouthparts of blood-feeding Arthropoda. In: Arthropod Structure & Development. Volume 41, No. 2, March 2012, pp. 101-118, doi: 10.1016 / j.asd.2011.12.001 .
  2. ↑ Ticks: the smaller, the more dangerous. In: Migros magazine . May 13, 2013, accessed July 19, 2016. «Nymphs are the most dangerous! ... During the metamorphosis to the next stage, the nymph loses 90 percent of its pathogens. "
  3. ↑ Press release from the Robert Koch Institute : Lyme borreliosis can be acquired in gardens. Results of a study in a district in the east of Brandenburg ( memento from October 7, 2014 in the Internet Archive ). On: rki.de from May 31, 2001, accessed on January 17, 2019.
  4. ^ Robert Koch Institute: Risk factors for Lyme borreliosis: Results of a study in a Brandenburg district. In: Epidemiological Bulletin . No. 21/2001, May 23, 2001, pp. 147–149 ( full text as PDF file ).
  5. ↑ Carolin Rauter, Rainer Oehme, Isabel Diterich, Matthias Engele, Thomas Hartung: Distribution of Clinically Relevant Borrelia Genospecies in Ticks Assessed by a Novel, Single-Run, Real-Time PCR. In: Journal of Clinical Microbiology. Volume 40, No. 1, January 2002, pp. 36-43, doi: 10.1128 / JCM.40.1.36-43.2002 .
  6. ↑ Monika Anthes, Beate Greindl: scaremongering with tick protection vaccinations. The irresponsible campaigns of the pharmaceutical industry. In: Report Mainz . May 4, 2009, accessed October 2, 2014.
  7. ↑ RKI advice for doctors: Early summer meningoencephalitis (TBE) . dated June 7, 2011, accessed October 2, 2014.
  8. ↑ How dangerous are ticks really? In: derStandard.at. April 12, 2007, accessed October 2, 2014.
  9. ↑ O. Kahl et al .: Risk of infection with Borrelia burgdorferi sensu lato for a host in relation to the duration of nymphal Ixodes ricinus feeding and the method of tick removal. In: Zentralblatt für Bakteriologie. Volume 287, No. 1-2, 1998, pp. 41-52. PMID 9532263 (study on the risk of infection depending on the duration of the sting and tick removal technique, FU Berlin ).
  10. ↑ Bavarian State Office for Health and Food Safety: How is a tick removed correctly? From: lgl.bayern.de , last update August 26, 2013, accessed on October 2, 2014.
  11. ↑ Working group for forestry services Hessen e. V .: Arbeitsschutzinfo 2/2009 - Tick protection. On: afl-hessen.de from 2009, accessed on October 2, 2014.
  12. ↑ L. Zenner, E. Drevon-Gaillott, MP Callait-Cardinal: Evaluation of four manual tick-removal devices for dogs. In: The veterinary record. Volume 159, 2006, pp. 526-529 doi: 10.1136 / vr.159.16.526
  13. ↑ A tick bite is an accident at work if it occurs while on duty . - Federal Administrative Court, judgment of 25 February 2010, the Federal Administrative Court 2 C 81.08, on: kostenlose-urteile.de with other decisions, accessed October 2, 2014.
  14. ↑ Joachim Gruber: Neuroborreliosis: Some background for the course of the disease and long duration of treatment . A literature compilation at: lymenet.de , February 1, 2008, accessed on October 2, 2014.

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