Detection of tick-borne pathogens by molecular methods

Abstract

Over the past two decades, tick-borne diseases have increased and now constitute a major health problem in many parts of Europe and North America, accounting for tens of thousands of new cases yearly in both regions. The most common of these diseases are tick-borne encephalitis, Lyme disease, anaplasmosis and babesiosis. According to the data of World Health Organization, in Lithuania the incidence of tick-borne encephalitis and Lyme boreliosis has markedly increased since 1990 and is the highest in Northern Europe. The study and identification of tick-transmitted pathogens is complicated as require investigation of all levels of the pathogen–host system – the pathogen, its competent vector and the reservoir host. Several methods have been developed for a direct detection of pathogens in infected vectors, host tissue, and clinical specimens from a patient. These include microscope-based assays, antigen detection assays, in vitro cultivation, and nucleic acid-based detection. However, detection methods such as culture isolation, dark-field microscopy and indirect antibody and antigen detection assays, are either time-consuming or prone to contamination, or have limited specificity and sensitivity. Using only phenotypic methods, it is impossible to resolve genetic differences among the different species of pathogens. In the recent years, molecular detection methods based on PCR amplification of the DNA of the pathogen have been shown to be effective for the diagnosis of tick-borne diseases and for elucidation of their epidemiology. Various polymerase chain reaction-based molecular methods, such as nested PCR, RFLP/PCR, Multiplex PCR, Real-time PCR, Real-time multiplex PCR, DNA–DNA hybridization analysis, nucleic acid sequence analysis have shown an increasing significance in the detection and typing of bacterial pathogens and parasitic protozoa. [...]