Babesia canis: evidence for genetic diversity among isolates revealed by restriction fragment length polymorphism analysis.

The genetic diversity of B. canis was investigated by restriction fragment length polymorphism analysis. For this purpose, we identified a Babesia canis specific DNA probe named pS8. This 1.2 kbp probe can detect as low as 20 pg of B. canis DNA. Results suggest that the pS8 probe is distributed in multiple copies throughout the genome though is probably not itself internally repetitious, i.e. not structured into blocks of tandem units. This probe reveals discrete hybridizing fragments in B. canis enzyme-digested genomic DNA. RFLP patterns obtained with the pS8 probe revealed a large genetic diversity between various isolates and led us to distinguish several clones derived from a single isolate. Results suggest that for a single isolate, the fingerprints obtained reflect those of a few quantitatively dominant clones. This technique can now be routinely applied and provides a convenient tool for the characterization and the identification of B. canis isolates, strains and clones.