Development of tools for molecular epidemiological studies in Babesia bovis

SCHNITTGER L, FLORIN-CHRISTENSEN

Simposio; ICTTD-2 Final Meeting; 2010

Development of tools for molecular epidemiological studies in Babesia bovis Leonhard Schnittger1,2 and Monica Florin-Christensen1,2 1Institute of Pathobiology, CICVyA, INTA-Castelar, Los Reseros y Nicolas Repetto, 1686 Hurlingham, Argentina; 2CONICET, Argentina. Bovine babesiosis is considered the economically most important arthropod-transmitted pathogen of of cattle on a global scale. The most virulent causative agent of this disease is Babesia bovis which is transmitted by Ixodid ticks and is often fatal for susceptible animals. In many affected countries, vaccination with attenuated parasite strains is applied to prevent outbreaks in areas of enzootic instability. Immunization is also used to protect animals when introduced from tick-free into tick-endemic areas. Occasionally, vaccine failures take place and can result in considerable economic losses, as has been reported by Australian researchers. One possible reason for these failures is the presence of Babesia field strains against which the vaccine strain is not protective. A pre-requisite to investigate this phenomenon is the availability of molecular markers that allow defining and distinguishing different Babesia strains. A few molecular markers and marker systems have been developed so far for B. bovis strains. Those based on size-polymorphism of PCR products and/or PCR-RFLP of single genes like msa-2, bvva1 and bv80 have been used to distinguish between parasite stocks and/or between parasite geographic isolates. Different groups have used RAPD (randomly amplified polymorphic DNA) for strain typification. It has been reported that RAPD is more discriminative than PCR- based tests targeting single genes. However, the clonality or composition of stocks can not be assessed with this method and results are often difficult to reproduce and interpret as co-amplification of host DNA may occur. Recently a multilocus typing system based on size polymorphism of short tandem repeats has been developed by our group. A hallmark of this system was that genetic distances between B. bovis multilocus genotypes corresponded with the geographic distance of their isolation. This system has the potential to be applied to investigate important parameters of B. bovis populations, like the occurrence and frequency of recombination, and the population structure of this parasite. The advances and challenges of the development of typing systems for B. bovis will be discussed.