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Lyme Disease - Epidemiology and Pathophysiology Abstract. Lyme disease is a zoonosis caused by the spirochete Borrelia burgdorferi and its genospecies. Its distribution includes Europe and some parts of North America. The dominant vector in Europe is the tick Ixodes ricinus. Its three developmental stages (larvae, nymph, adult) take blood meals from small rodents, birds, and deer, some of which may also host B. burgdorferi . This is how the majority of the ticks become infected. Transmission of the pathogen to a new host occurs via tick saliva at the next blood meal, which induces phenotypical modifications of the spirochete that facilitate migration from the tick intestine to the salivary gland and survival in the vertebrate host. Both, tick saliva and the remodeled surface proteins of the bacteria, provide protection from the host's immune system. Dissemination occurs predominantly via the hematogenous route, but motility of the spirochete facilitates tissue migration. The species-dependent tropism for skin, joints and neuronal structures appears to be mediated by specific interactions between host and pathogen proteins. While extrapolated total cases of Lyme disease in Switzerland have remained stable over the past years, areas where infected ticks can be found have expanded. Milder winters and higher temperatures may explain this observation. In addition to measures helping to avoid tick bites, vaccines may contribute to protect against Lyme disease in the future. A promising, multivalent, protein-based vaccine appears to provide protection from several subspecies of B. burgdorferi .

The Less Frequent Tick-borne Infections in Central Europe Abstract. The incidence of tick-borne infections is increasing, the endemic areas of tick vectors are expanding, novel tick-borne pathogens have been identified, and known pathogens are emerging in new geographic areas. This review focuses on the less frequent tick-borne pathogens in Central Europe, including Anaplasma , Babesia , Borrelia miyamotoi , Candidatus Neoehrlichia mikurensis , Ehrlichia , Francisella tularensis , Rickettsia , relapsing fever spirochetes, and tick-borne viruses. Travel-associated infections are also considered emphasizing a clinical and geographic approach. In addition to the most frequent Ixodes sp. also other tick species transmitting human pathogens are endemic in Europe. Clinicians should maintain suspicion for tick-borne diseases in patients presenting with fever of unexplained cause, with acute rash or with febrile neurological signs and symptoms. Because clinical manifestations of tick-borne infections are nonspecific - except for Erythema migrans - it is important to consider tick-borne illnesses even without a reported tick exposure or a suggesting travel history. Less than 50% of infected patients are aware of a tick-bite. Patients' history must include profession, leisure time activities, travel, and immune status. Tick-borne diseases may have a severe and life-threatening course in immunocompromised and splenectomized persons.

Among the various species of hard ticks, Ixodes ricinus is the most frequently found tick throughout Europe. As with other ixodid ticks, the developmental cycle runs through three stages. In each stage a blood meal is required in order to develop to the next stage. Ixodes ricinus has been found to feed on more than 300 different vertebrate species. Usually, larval ticks feed on small mammals such as mice and become infected with various microorganisms and viruses, of which some are substantial pathogens to humans. The pathogens remain in the tick during molting and are thus transstadially transmitted to the next developmental stage. Pathogens transmitted to humans are the agents of Lyme borreliosis, the tick-borne encephalitis virus, Rickettsia species, Anaplasma phagocytophilum, occasionally Francisella tularensis, and protozoal Babesia species. Within the scope of an EU project Ixodes ricinus ticks from all federal states of Austria were searched by means of PCR methods for bacterial pathogens such as Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato, Coxiella burnetii, Ehrlichia spp., Francisella tularensis, Rickettsia spp., and protozoal Babesia. Additionally, the prevalence of Bartonella spp. in this tick species was also determined. Besides the singular detection of Coxiella burnetii and Francisella tularensis in one tick collection site the overall prevalence of Anaplasma phagocytophilum, borreliae, rickettsae and babesiae in Ixodes ricinus amounted to 15%, 14%, 6% and surprising 36% and 51%, respectively. Bartonellae were detected in about 7%.

Large areas of the Central European country Austria are known to be endemic for tick-borne encephalitis virus (TBEV). However, so far only limited data are available for the prevalence, distribution and species composition of rickettsiae of the spotted fever group in Austria. In the present study 306 ticks were collected in summer 2007. Location of sampling was Neudörfl, a known TBEV endemic area in the district of Burgenland in Eastern Austria. 286 ticks belonged to the species Ixodes ricinus and 20 ticks were identified as Dermacentor spp. Detection of TBEV and rickettsial species was done by polymerase chain reaction. We were not able to detect TBEV in any of the ticks examined. However 16 ticks, exclusively of the species Ixodes ricinus showed positive results for rickettsiae. 14 out of 16 rickettsia-positive ticks contains sufficient DNA for a sequence determination. The sequencing of the citrate synthase genes resulted exclusively in the identification of Rickettsia helvetica. The results show that TBEV was not at all or in a low frequency circulating in a known endemic area in summer 2007. However, for the first time the prevalence of 5.7% of Rickettsia helvetica was determined in a tick population in Eastern Austria.

More than 800 tick species have been reported world-wide however only about 30 tick species feed on humans, among them Ixodes ricinus, which is the most frequent tick species biting humans in Europe. It is the vector of Borrelia burgdorferi, which causes Lyme disease and of the tick-borne encephalitis virus. I. ricinus ticks pass through three developmental stages: larvae, nymphs and adults (females and males). More than 300 animal species have been reported as natural hosts for I. ricinus and 50 vertebrate species have been identified as reservoir hosts for B. burgdorferi. The density of this tick species may be very high, reaching in some places more than 300 ticks/100 m2. Attached ticks should be removed without delay with a blunt forceps.

Tick-borne zoonotic pathogens are well known in many areas all over the world. Among the tick-borne transmitted diseases in Switzerland, Lyme disease caused by Borrelia burgdorferi, ehrlichiosis caused by various species of Ehrlichia and tick-borne encephalitis caused by the tick-borne encephalitis virus (TBEV) are the most important zoonotic diseases. Early diagnosis and treatment is necessary to prevent fatal infections and chronic damage to various tissues. Due to the variety of uncharacteristic clinical signs, tick-borne diseases are not easily recognized. Diagnosis is based on clinical findings, a record of tick exposure, and direct or indirect detection of the pathogen. Here we discuss briefly the most important tick-borne infections and their diagnosis with emphasis on a new molecular diagnostic tool--the real-time TaqMan PCR--and its importance for the diagnosis of tick-borne pathogens.

HGE is an uncommon zoonosis, transmitted to humans by ticks (Ixodes ricinus). Heavily exposed persons, such as foresters and forestry workers, are most at risk of infection. HGE usually runs an asymptomatic and self-limiting course. Symptoms include acute pyrexial illness, frequently accompanied by muscle pain, headache, nausea and vomiting. Treatment is with doxycycline/tetracycline or rifampicin. In a study in Hesse of 128 heavily exposed subjects, 19.5% had serum antibodies (IFA test) against HGE versus 4.4% in a control group. This difference is statistically significant. The prevalence of both symptoms and the seropositivity differ significantly between locations. HGE should be considered in the differential diagnosis of fever of unknown origin following tick bite exposure, at least in the North Hesse region.