New data on epizootiology and genetics of piroplasms based on sequences of small ribosomal subunit and cytochrome b genes.

As a continuation of our studies on molecular epizootiology of piroplasmosis in Spain and other countries, we present in this contribution the finding of new hosts for some piroplasms, as well as information on their 18S rRNA gene sequences. Genetic data were complemented with sequences of apocytochrome b gene (whenever possible). The following conclusions were drawn from these molecular studies: Theileria annulata is capable of infecting dogs, since it was diagnosed in a symptomatic animal. According to cytochrome b sequences, isolates from cows and dog present slight differences. The same isolates showed, however, identical sequence in the 18S rRNA gene. This exemplifies well the usefulness of the mitochondrial gene for examining infra-specific variation. Babesia bovis is an occasional parasite of equines, since it was detected in two symptomatic horses. We found evidence of genetic polymorphism occurring in the 18S rRNA gene of Spanish T. equi-like and B. ovis isolates. B. bennetti from Spanish seagull is loosely related to B. ovis, and might represent a genetically distinct branch of babesids. A partial sequence of a cytochrome b pseudogene was obtained for the first time in Babesia canis rossi from South Africa. The pseudogene is distantly related to B. bigemina cytochrome b gene. These new findings confirm the ability of some piroplasms to infect multiple hosts, as well as the existence of a relatively wide genetic polymorphisms with respect to the cytochrome b gene. On the other hand, the existence of mtDNA-like pseudogenes of possible nuclear location in piroplasms is interesting due to their possible impact on molecular phylogeny studies.