Prevalence of Babesia and Anaplasma in ticks infesting dogs in Great Britain

Ticks are important vectors of disease in companion animals and transmit an extensive range of viral, bacterial and protozoan pathogens to dogs and cats. They may also be vectors of zoonotic pathogens which affect the health of in-contact owners. In recent years, babesiosis, and anaplasmosis have all shown signs of increased prevalence and distribution in various parts of Europe. Here, the prevalence of Anaplasma spp. and Babesia spp. pathogens in Ixodes ticks, collected from dogs in the UK in 2009, were evaluated using PCR and sequence analysis of the 16S rDNA or 18S rDNA regions respectively. Species identification was performed by alignment with existing sequences in GenBank. After sequencing, 5 out of 677 tick samples (0.74%) contained rDNA which shared 97-100%% sequence homology with Anaplasma phagocytophilum. Of these, three samples came from Ixodes ricinus and two from Ixodes hexagonus. Sixteen out of 742 ticks (2.4%) were positive for Babesia and of these 11 showed 97-100% homology with B. gibsoni. All of these 11 samples were derived from I. ricinus. One sample, again from I. ricinus, showed 99% homology for B. divergens. Four of the Babesia spp sequences were of the "venatorum" or EU1 type, three of which came from I. ricinus and one from an Ixodes canisuga. This strain has been associated with severe human cases of babeisiosis. A further 246 positive results, which appeared to show the presence of Anaplasma following PCR, were shown by sequence analysis to be derived from the bacterium Candidatus "Midichloria mitochondrii", which to date has been assumed to be non-pathogenic. The results are of interest because the presence of B. gibsoni in the UK further confirms the worldwide distribution of this piroplasm and supports the inference that I. ricinus may act as a vector for Babesia of the gibsoni-complex.