Diversity of Babesia in Ixodes ricinus ticks in Poland

The aims of this study were: (1) to estimate Babesia prevalence in the most common species of tick in Poland, Ixodes ricinus, in two recreational areas (Urwitałt in the Mazury Lake District and Bielański Forest in Warsaw), and (2) to evaluate the molecular diversity of Babesia isolates in questing I. ricinus in Poland.

Questing ticks were collected from vegetation in forest areas in Urwitałt near Mikołajki and in Bielański Forest (Warsaw). Purified genomic DNA was used with specific primers to amplify a fragment of the Babesia spp. 18S rRNA gene.

Tick-drag indices for I. ricinus were high in both study areas, reaching somewhat higher values in Urwitałt than in Bielański Forest. The overall prevalence of Babesia spp. in examined ticks was 1.6%. In Urwitałt, two strains of B. microti were identified using rRNA sequences: the enzootic Munich strain and an isolate close to the zoonotic Jena strain. The proportion of infections due to these two strains in questing ticks reversed over a six-year period. During 3 years of study in Bielański Forest, all Babesia isolates obtained from I. ricinus were identical to Babesia sp. EU1 (B. venatorum), previously recognized as an agent of human babesiosis.

This study has confirmed the presence of enzoonotic and zoonotic Babesia species/strains in the abundant human-biting tick I. ricinus in recreational areas in Poland. It has also shown that the distribution of different genotypes has changed over time, however the reasons for these fluctuations still remain to be investigated.