Navigation und Service

Caution ticks! - The "common tick" can be dangerous for humans and animals

15/2001, 27.04.2001

A TBE vaccination is a must when travelling to high-risk areas

The "common tick" (Ixodes ricinus) is a tough case. "When the tick is infected with the corresponding pathogen, a bite can suffice in order to transmit Lyme borreliosis, spring-summer encephalitis (also known as TBE - tick-borne encephalitis), ehrlichiosis, Q fever or babesiosis to humans and animals", according to the lecturer, Dr. Jochen Süss, Head of the National Reference Laboratory for Tick-borne Diseases within BgVV. Their relevance for health was the subject of the 6th International Potsdam Symposium on Tick-borne Diseases which was staged in Berlin on 26 and 27 April. Around 150 guests from 22 countries discussed questions of epidemiology, ecology, prophylaxis and treatment at the BgVV conference.

In Germany 50,000 to 60,000 people contract Lyme borreliosis every year and a further 150 to 200 tick-borne encephalitis (TBE). Effective vaccination is available for TBE which BgVV recommends to all people who live, work or spend some time during their vacation in risk areas. The vaccine is contraindicated for children under the age of 12; no other vaccine has been authorized at present in Germany for administration to children. There is no vaccination against Lyme borreliosis even today. Protection against tick bites through appropriate clothing or effective defence mechanisms is, therefore, the best way of protecting children from infection.

Lyme borreliosis is the most frequent cause of tick-borne disease in humans in Europe and the USA. In Germany 10 to 30% of ticks are infected with the bacterium Borrelia burgdorferi. There are no specific risk areas. When diagnosed early borreliosis can be successfully treated with antibiotics. If the infection is not diagnosed, diagnosed too late or treated with an inadequate or overly short course of antibiotics, a chronic course of the disease may develop affecting the nervous system, joints and heart which is difficult or even impossible to treat. Prophylactic vaccination, which has been available in the USA for 2 ½ years, is promising but does not cover the German spectrum of pathogens. Work is currently being undertaken in Germany on developing an effective vaccine. It could be available in about two years' time for prophylactic administration.

TBE is an infectious disease which leads to disorders in the cerebral membranes, the brain and medulla with, in some cases, a serious course of the disease. It occurs in numerous European countries with very varied infection risks. Only the United Kingdom, the Iberian Peninsula and the Benelux countries are free from TBE. Denmark (with the exception of Bornholm), Italy (with the exception of Florence), Greece (with the exception of Thessaloniki) and France (with the exception of Alsace) are largely free. In all other European countries TBE is more or less widespread. Particularly in the Baltic States, which are considered to be high-risk countries, the infection rates are again on the increase. In Germany this also applies to Baden-Württemberg and Bavaria. Up to 5% of ticks are infected with the TBE virus there. The risks are smaller in Odenwald and in the Rhineland-Palatinate. Inhabitants in (high) risk areas are particularly at risk from TBE as are all individuals who travel to such areas, hike, camp or pursue leisure activities in nature during the tick season. Around 70% of the people bitten by an infected tick, show few or no symptoms. In around 30% of cases serious diseases do occur. 1 to 2% of these individuals die in the course of the infection. There is no specific therapy. The symptoms are treated. Against this backdrop, the participants in the seminar felt there was an urgent need for a vaccine to be made available as soon as possible again in Germany which can be given to children.

Participants from Austria reported on successes with a consistent protective vaccination. The vaccination rate is now more than 90%. The number of TBE cases could thus be reduced from more than 1,000 to well under 100. In particular, the vaccination of children has proven its worth. Whereas in the past up to 25% of all TBE cases occurred in children under the age of 14, today they only account for 4.5%.

In contrast to Lyme borreliosis and TBE, the importance of ehrlichiosis, Q fever and babesiosis transmitted by ticks is still largely unknown. Ehrlichiosis is a multi-organ disease which runs a mild course in most cases. In studies in Baden- Württemberg the pathogen was detected in around 3% of ticks; 5 to 15% of 4,000 forest workers had antibodies in their blood. Disorders with Q fever go hand in hand with a high temperature, severe head and muscular pain. The infection can be treated with antibiotics. Babesiosis known in animals is becoming more relevant for humans. The pathogen (Babesia divergens) triggers a malaria-like infection with a high temperature, anaemia, blood in urine and hepatitis. All cases described up to now in Europe occurred in individuals whose spleen had been removed and normally proved fatal after renal insufficiency.

Ticks can constitute a risk as a pathogen not only for humans but also for pets like dogs and horses. The first cases of a tick-borne disorder of the central nervous system caused by the TBE virus or by Borrelia burgdorferi frequently occur in dogs already in the spring. The number of cases peak in June and July, fall slightly during the dry summer months and go back up in the autumn. The fact that many people take their pets on holiday with them contributes to the spread of the disease. France, Germany and Sweden are considered to be new endemic areas for tick-borne encephalitis for which there is no vaccination even today. The animals' symptoms are treated. By contrast, in Germany vaccines are available for the prophylaxis of Lyme borreliosis for dogs but they do not adequately cover the spectrum of pathogens. Animal owners should not, therefore, renounce (additional) protection against ticks by using tick-repellant agents.

In principle, it can be said that the probability of infection of humans and animals increases with the duration of the tick bite. Ticks should, therefore, be immediately removed with tweezers. The direction in which the tweezers are turned is not important. Never apply wax, nail polish or the like to the tick as it can trigger an increased release of pathogens. With a few exceptions, many protective agents are either ineffective against ticks or only offer protection for a limited period of time. The best protection against ticks is suitable clothing (light garments on which the ticks are readily visible, long trousers, long sleeves) when people do not want to or cannot keep away from tick biotopes.

Short versions of the seminar contributions are available on the BgVV homepage on www.bgvv.de.

Up