Title Information

Bayerische Akademie der Wissenschaften (editor):

Zur Ökologie von Infektionskrankheiten:

Borreliose, Frühsommermeningoenzephalitis (FSME) und Fuchsbandwurm

Rundgespräch am 11. Oktober 2004

Contents

Lecturers and discussants

Betke, Klaus, Prof. Dr. med., Lochham

Bischhoff-Miersch, Andrea, Wissenschaftsjournalistin, München

Brehm, Klaus, Priv.-Doz. Dr., Institut für Hygiene und Mikrobiologie, Universität Würzburg, Würzburg

* Bulirsch, Roland, Prof. Dr., Bayerische Akademie der Wissenschaften, Mitglied des Vorstands, München

* Dobler, Gerhard, Dr. med., Institut für Mikrobiologie der Bundeswehr München, München

Elstner, Erich, Prof. Dr., Technische Universität München, Lehrstuhl für Phytopathologie, Freising

* Fingerle, Volker, Dr. med., Nationales Referenzzentrum für Borrelien, Max-von-Pettenkofer-Institut der Universität München, München

Frühwein, Nikolaus, Dr. med., Präsident der Bayerischen Gesellschaft für Immun-, Tropenmedizin und Impfwesen e.V., München

* Gerards, Hans Hubert, Dr. med., GlaxoSmithKline GmbH & Co. KG, München

Gietl, Christine, Priv.-Doz. Dr., Technische Universität München, Lehrstuhl für Botanik, Biologikum, Freising

Haber, Wolfgang, Prof. Dr., Mitglied der Kommission für Ökologie, Technische Universität München, Lehrstuhl für Landschaftsökologie, Freising

Herm, Dietrich, Prof. Dr., Mitglied der Kommission für Ökologie, Pullach

Hofmann, Heidelore, Prof. Dr. med., Technische Universität München, Klinik und Poliklinik für Dermatologie und Allergologie, München

Hoppe, Brigitte, Prof. Dr., c/o Universität München, Geschichte der Naturwissenschaften, München

Just, Frank, Dr. med. Dr., Universität München, Institut für vergleichende Tropenmedizin und Parasitologie, München

Kandler, Traudl, Dr., München

Knorr, Dietrich, Dr., Gilching

* König, Andreas, Dr., Technische Universität München, Wissenschaftszentrum Weihenstephan, Fachgebiet Wildbiologie und Wildtiermanagement, Freising

Kutzschenbach, Peter von, Dr. med., Vaterstetten

* Löscher, Thomas, Prof. Dr. med., Abteilung für Infektions- und Tropenmedizin der Universität München, München

* Mutius, Erika von, Prof. Dr. med., Mitglied der Kommission für Ökologie, Dr. v. Haunersches Kinderspital der Universität München, Klinikum Innenstadt, München

Neiss, Albrecht, Prof. Dr., Technische Universität München, Institut für Medizinische Statistik und Epidemiologie, München

* Pohl-Koppe, Annette, Priv.-Doz. Dr. med., Dr. v. Haunersches Kinderspital der Universität München, Klinikum Innenstadt, München

Prestele, Jakob, Technische Universität München, Institut für Botanik, Biologikum, Freising

Rehm, Norbert, Dr., Vet. Dir., Bayerisches Staatsministerium für Umwelt, Gesundheit und Verbraucherschutz, Ref. Tierseuchenbekämpfung, München

* Reichholf, Josef H., Prof. Dr., Mitglied der Kommission für Ökologie, Zoologische Staatssammlung, München

Sauer, Hans Dieter, Wissenschaftsjournalist, Gräfelfing

Sauter, Ulrich, Dr., Forstdirektion Oberbayern-Schwaben, Augsburg

Schneider, Dietrich, Prof. Dr., Starnberg

* van der Sant, Dirk, Dr., Landesjagdverband Bayern e.V. (BJV), Geschäftsstelle, Feldkirchen

Ziegler, Hubert, Prof. Dr., Vorsitzender der Kommission für Ökologie, Bayerische Akademie der Wissenschaften, München

Vorwort

Durch Tiere auf den Menschen übertragene Infektionskrankheiten, so genannte Zoonosen, sind in den letzten Jahren aufgrund ihrer Zunahme verstärkt in den Blickpunkt des Interesses gerückt. Zwar sind die zugrunde liegenden biologischen Systeme aus Wirtstier und von diesem auf den Menschen übertragenen Parasit (z.B. Fuchsbandwurm oder Zecke) meist seit langem bekannt und es liegen von medizinischer Seite viele Daten z.B. über Zunahme und geografische Ausbreitung der Krankheiten vor. Es fehlen aber oft neuere Untersuchungen zur Ökologie und zur Verbreitung der Wirtstiere, z.B. zu möglicherweise verändertem Fress-, Jagd- oder Brutverhalten aufgrund von in den letzten Jahren oder Jahrzehnten veränderten Umweltbedingungen. Sofern derartige ökologische Daten vorhanden sind, fehlt zudem oft ihre Verknüpfung mit den entsprechenden medizinisch-epidemiologischen Daten.

Die Brücke zwischen Medizin und Epidemiologie einerseits und Ökologie andererseits zu schlagen, war Ziel des Rundgesprächs »Zur Ökologie von Infektionskrankheiten: Borreliose, FSME und Fuchsbandwurm«. Aus der Fülle der weltweit für den Menschen bedeutenden Zoonosen wurden dabei nur exemplarisch einige wenige Beispiele herausgegriffen, die speziell in Mitteleuropa von Bedeutung sind (bzw. dort noch vor kurzem von Bedeutung waren) und durch wild bzw. frei leben­de Tiere übertragen werden: Die Übertragung des Malaria-Erregers durch die Anopheles-Mücke, die Übertragung des Fuchsbandwurms sowie die Übertragung von Zecken mit Borreliose- oder FSME-Erregern durch Wild und andere frei lebende Tiere.

Das vorliegende Buch enthält die Vorträge und Diskussionen dieser Tagung, ergänzt durch eine Zusammenfassung. Es richtet sich gleichermaßen an Fachleute wie an interessierte Laien und soll neben dem aktuellen Wissensstand auch Handlungsmöglichkeiten sowie Forschungslücken aufzeigen.

Abstracts

Thomas LÖSCHER: Malaria in Europe: Historical review and outlook

[14 pp., 7 black-and-white figures, 8 tables]

Until the second half of the 19th century, malaria has been endemic in many parts of Europe. Large-scale drainage of mosquito breeding sites and other control measures succeeded in the eradication of malaria in Europe in the middle of the 20th century. However, malaria is a re-emerging disease in some of the new independent states in the south of the former Soviet Union. Today, malaria is mainly a problem of developing countries in the tropics. Subsaharan Africa carries the main burden of 200-300 million cases and 1-2 million deaths caused by malaria each year. In Europe, malaria has become an important disease in international travellers. Resistance of Plasmodium falciparum against many of the available antimalarials is now a major problem in endemic countries. This also affects the efficacy of chemoprophylaxis in travellers. Recently, enormous advances in malaria research have been achieved, e.g., the full genomic sequences of P. falciparum and of Anopheles are available now. This may well provide the basis for the development of better tools to combat malaria, like new drugs and the development of an efficient vaccine.

Volker FINGERLE: Epedmiology and microbiological diagnosis of Lyme borreliosis: between myths and facts

[14 pp., 6 black-and-white figures, 2 tables]

Tick-borne diseases, especially Lyme borreliosis, increasingly gain public awareness in recent years as shown by rising reports by the daily press, set up of more than 50 Lyme borreliosis self-help groups with more than 10,000 volunteers, and establishment of an unmanageable number of sources of information in the internet. Lyme borreliosis caused by the spirochete Borrelia burgdorferi s.l. in Germany is a numerous, in rare cases severe infectious disease, every year responsible for spectacular reports in the media and internet: “only treatable in early stage”, “typically chronic course”, and “diagnosis always difficult” are only some of the wide spread thinkings about this disease. By contrast, based on controlled scientific studies, it can be deduced: Lyme borreliosis mostly has an excellent prognosis, and, following mandatory guidelines, diagnosis as well as therapy predominantly is efficient. Severe chronic cases are the exception.

For diagnosis of Lyme borreliosis official guidelines based on controlled studies and expert opinion are available for medical proceeding. For the ambitious microbiological diagnosis serological diagnosis in a step-wise manner is most important. Further methods (offered from specialized laboratories) include cultivation of the pathogen and polymerase chain reaction (detection of pathogen DNA). Thereby heterogeneity of B. burgdorferi s.l. constitutes a major problem for all methods. However, it is to emphasize that sensitivity of antibody detection in chronic manifestations of Lyme borreliosis nearly reaches 100 %.

Methods that actually can not be recommended include the lymphocyte transformation test, the visual contrast sensitivity test, and detection of borreliae in ticks detached from humans.

Gerhard DOBLER, Sandra ESSBAUER, Roman WÖLFEL und Martin PFEFFER: Interaction of ecology and epidemiology, considering tick-borne encephalitis (TBE)

[10 pp., 6 black-and-white figures]

Tick-borne encephalitis is a virus infection which can cause symptoms of the central nervous system in humans. It is circulating in a natural cycle between ticks and rodents. Humans are not part of the natural virus transmission cycle. However, they can influence the existence and the intensity of natural cycles by creating favourable or non-favourable natural conditions. Penetration of humans into the ecological niche of the virus is a prerequisite for human infection. The penetration of humans and the hereby caused number of human infections are influenced by social, economic and population dynamic factors. So far vaccination against TBE is the only available method effective for individual and population protection. Therefore, aspects of health policy (general vaccination policy, acceptance of vaccines, acceptance of TBE vaccine) play an important role in the epidemiology of TBE, too. The recognition of these socio-epidemiological factors and directed change of behaviour can contribute to decrease incidence of TBE in the population and protect individuals.

Annette POHL-KOPPE: Symptoms, course and diagnosis of Lyme disease and tick-borne encephalitis

[9 pp., 5 black-and-white figures, 2 tables]

Tick-borne encephalitis and Lyme disease are vector-borne infectious diseases that are transmitted by the tick Ixodes ricinus. Lyme disease is caused by the spirochete Borrelia burgdorferi. Characteristically there are three stages of disease: after few days to weeks the acute, localized infection leads to the development of an erythema chronicum migrans at the site of the ticke bite (stage I). After an incubation period of several weeks to months the infection may proceed to an acute systemic stage resulting in diverse clinical manifestations (stage II): multiple erythemata migrantia, Borrelial lymphocytoma, acute neuroborreliosis, Lyme arthritis and, very rare, carditis. If stage I or II manifestations are not treated with antibiotics, a chronic systemic infection may develop (stage III) with acrodermatitis chronica atrophicans, chronic neuroborreliosis or chronic Lyme arthritis. In the diagnosis of Lyme disease, both clinical aspects and laboratory methods are important. Particularly the Lyme serology may show unusual patterns in some individuals. Lyme disease is treated with antibiotics. The antibiotic treatment is dependent on the age of the patient, the stage of the disease and the clinical manifestation. There is no currently available vaccine.

Tick-borne encephalitis is caused by a flavivirus. Dependent on the activity of ticks there is a peak of disease during the summer and autumn months. After an incubation period of 7-14 days, 30 % of the infected persons develop flu-like symptoms. One week after this prodomal stage about 10 % of infected persons show involvement of the central nervous system. In children, the clinical course of tick-borne encephalitis is generally milder. In adults, lethal courses of the disease may occur in 1-2 %, neurologic deficits may develop in up to 10-20 % of the patients. The disease is diagnosed by serological methods. There is no specific treatment. Persons with an exposure risk should receive an active immunization.

Hans Hubert GERARDS: What do we know about the extension of the Alveolar Hydatid Disease (echinococcosis)?

[8 pp., 2 black-and-white figures, 1 table]

Alveolar echinococcocis caused by Echinococcus multilocularis (metacestode stage of the pathogen) is a rare but dangerous human infection. Man represents an aberrant host in the life cycle of the worm. A special characteristic of the disease is the long incubation time of about 10 years. The liver is almost exclusively its primary site (> 90 %). Although surgery and chemotherapy are both recommended for treatment their effectiveness is regarded as moderate only. In the late stage of the disease, it shows some similarities with a malign tumor. In 1998, a national registry was founded and there has been duty of notification since 2001. Southern Germany is particularly affected by alveolar echinococcosis, due to a steady increase in the number of foxes as well as the growing rate of infected foxes.

Andreas KÖNIG: New research findings on the expansion of the fox tapeworm (Echinococcus multilocularis) in Munich and its environs

[16 pp., 8 black-and-white figures, 11 tables]

The fox tapeworm has been a matter of concern to the public since the early nineties of the last century. The reactions of the individual federal states affected have however been very varied. Whereas in Baden-Wurttemberg the problem was taken up intensively at an early stage, it was given only little attention in Bavaria. Therefore differentiated research approaches and comprehensive basic data are lacking in Bavaria. In 2002 the Technische Universität München, in conjunction with Hohenheim University, were asked to carry out a risk analysis on “the fox tapeworm” in the Starnberg region. The analysis was ordered by the mayors of this region, and three mayors from neighbouring Munich. On average, every second fox carried the tapeworm: in some parts of the region investigated, as many as 80 % of the animals were infected. These results now caused renewed debate in Bavaria, too, on the danger presented by the parasite.

It would be tempting to use the small number of human cases of infection – in Bavaria 4 patients a year – as a starting point for evaluation, but this does not take into consideration the long incubation period of 10 to 15 years between infection and breakout of the illness. Within this period foxes have not only made urban areas their habitat: the fox population has also trebled, and infection rates with fox tapeworm within this population have doubled. The risk of infection for us people can now be assumed to be 7 times higher than 10 to 15 years ago, when 3-4 citizens in Bavaria became infected per year. Given treatment costs of at least 300 000 € per patient, the economic damage amounts to approximately 6 million € per year.

Instead of using this sum solely for therapy, it could be used preventatively for worming measures and education programmes. Through such measures, human suffering could be avoided. The main emphasis for the worming measures must be on cities and villages, as not only do many foxes live with the tapeworm in these areas, but many people also come into close contact with these foxes and their excretions here. In the community of Grünwald it has been shown since 2001 that these worming programmes can sustainably reduce infection rates to almost 0 %.

Dirk VAN DER SANT: Population development of major vector species from a wildlife biologist’s point of view.

[14 pp., 15 black-and-white figures, 1 table]

At present the subject can’t be answered satisfactorily. Population analyses based on population density and composition are only possible for view selected species. Due to missing data it is not possible to draw a conclusion about the character and the structure of populations for common wildlife species such as red fox, stone marten or roe deer. The shooting data presented below are very one-sided results in principle. They only concern animals, which were shot and thus no longer add to the population. In spite of these insufficiencies of shooting data, nevertheless several conclusions can be drawn. On a long-term basis (at least over a period of ten years) general tendencies of population development can be derived from shooting data. However, potential factors, e.g. changing shooting right or wildlife management, must be regarded thereby.

On principle, due to the obligation of public welfare it has to be acted on the assumption that game as well as parasites and diseases transmitted by game pose a thread. If it is not possible to intensify the shooting of potential carriers of diseases, also complementary solutions must be initiated.

The facts given in this article cannot describe all aspects of the theme in detail, but it is shown in which discrepancy the acquisition, the analysis, and the interpretation of the data are. Conclusions concerning a possible risk of disease transmission from game to man can only be assumed. With growing population densities, however, also the risk of disease transmission is definitely growing.

Josef H. REICHHOLF: Tick distribution and trends of frequency of tick-transmitters in urban, rural and woodland areas

[10 pp., 13 black and whgite figures]

Incidences of Lyme disease, tick-born encephalitis (FSME) and infections with the fox tapeworm obviously increased in Bavaria as in other regions of Central Europe in recent decades. But it is not clear yet, to what extent this has been caused by improved diagnosis or by a real increase in the number of infections. Data on population density and development of ticks and tick-bearing animals are scarce. Only for species of game the hunting lists provide some information, but due to seasonal restrictions or the hunters’ interests they may not reflect real population trends.

Studies in the city of Munich and the surroundings provide some more information, just as do the long-term registrations of road casualties along a stretch of Federal road of 150 kilometres from Munich eastwards through Southern Bavaria. The main results are shown in the figures. Tick frequency is about 15 times higher in urban gardens and parks compared to natural forests south of Munich, but by far the greatest numbers of ticks are found close to feeding lots for game in the forests.

Hedgehogs may be an important reservoir for urban tick populations because they are much more frequent (about 10 times) in gardens and in the transitional zones to the countryside than they are in fields and forests. The like applies to feral cats and stone martens. Contrary to the hunting lists, fox numbers might have decreased recently. Carnivores in general are much more frequent in urban areas than in the forests, so with respect to the fox tapeworm it may not be enough to concentrate the attention on the foxes in order to control this dangerous infection. Numbers and changes in frequency of free-living mammals in urban areas, therefore, should be studied much more thoroughly in respect to their possible function as vectors of worms and tick-borne diseases.