Among the 20 tick species described in Switzerland, Ixodes ricinus, the most
frequent one, is implicated in the transmission of pathogenic agents. Lyme
borreliosis and tick-borne encephalitis (TBE) are the major tick-borne
diseases transmitted to human. 
**Presently 5 Borrelia species, belonging to the group Borrelia burgdorferi,
are recognized as human pathogens**. 
The risks of infection depend on the stage of the vector, the multiple
hosts, the pathogenic agent, as well as human behavior in nature. 
The detection of other pathogenic agents in ticks: Anaplasma, Babesia and
Rickettsia predispose to infections or co-infections. Results of
sero-epidemiologic studies suggest human infections. Active surveillance by
physicians is necessary and clinical studies are required to evaluate the
importance of these infections in Switzerland.

Excerpt:

Lizards are considered zooprophylactic for almost all Borrelia burgdorferi species, and act as dilution hosts in parts of North America. Whether European lizards significantly reduce the ability of B. burgdorferi to maintain itself in enzootic cycles, and consequently decrease the infection rate of Ixodes ricinus ticks for B. burgdorferi and other tick-borne pathogens in Western Europe is not clear.

Results

Ticks were collected from sand lizards, their habitat (heath) and from the adjacent forest. DNA of tick-borne pathogens was detected by PCR followed by reverse line blotting. Tick densities were measured at all four locations by blanket dragging. Nymphs and adult ticks collected from lizards had a significantly lower (1.4%) prevalence of B. burgdorferi sensu lato, compared to questing ticks in heath (24%) or forest (19%). The prevalence of Rickettsia helvetica was significantly higher in ticks from lizards (19%) than those from woodland (10%) whereas neither was significantly different from the prevalence in ticks from heather (15%). The prevalence of Anaplasma and Ehrlichia spp in heather (12%) and forest (14%) were comparable, but significantly lower in ticks from sand lizards (5.4%). The prevalence of Babesia spp in ticks varied between 0 and 5.3 %. Tick load of lizards ranged from 1 – 16. Tick densities were ~ 5-fold lower in the heather areas than in woodlands at all four sites.

Known or suspected mechanisms of persistence in babesial parasites include cytoadhesion and rapid
variation of the adhesive ligand in Babesia bovis and genetic diversity in
several merozoite stage proteins of different Babesia spp. In Anaplasma,
extensive variation in the pfam01617 gene family accompanies cycling of organism
levels in chronic infection. One result from the pioneering research at
Onderstepoort is the definition of a related polymorphic gene family that is
likely involved in immunity against heartwater disease. We are beginning to
understand the sizes of the antigenic repertoires and full definition is close,
with the possibility of applying simultaneous high-throughput sequencing to the
order of 1000 small genomes. We also, for the first time, can consider modifying
these genomes and looking at effects on persistence and virulence. However,
important biological questions remain unanswered; for example, why we are seeing
a new emerging Anaplasma infection of humans and is infection of endothelial
cells by Anaplasma significant to persistence in vivo.

http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=19967928&retmode=ref&cmd=prlinks
PMID: 19967928  [PubMed – in process]

Onderstepoort J Vet Res. 2009 Mar;76(1):53-8.

Persistence mechanisms in tick-borne diseases.

Barbet AF.

Department of Infectious Diseases & Pathology, College of Veterinary Medicine,
University of Florida, Gainesville, Florida, USA.