A Comparative Genomic Study of Attenuated and Virulent Strains of .

Cattle babesiosis is a socio-economically important tick-borne disease caused by Apicomplexa protozoa of the genus that are obligate intraerythrocytic parasites. The pathogenicity of parasites for cattle is determined by the interaction with the host immune system and the presence of the parasite's virulence genes. A strain that has been maintained under a microaerophilic stationary phase in in vitro culture conditions for several years in the laboratory lost virulence for the bovine host and the capacity for being transmitted by the tick vector. In this study, we compared the virulome of the in vitro culture attenuated strain (S) and the virulent tick transmitted parental Mexican strain (M). Preliminary results obtained by using the Basic Local Alignment Search Tool (BLAST) showed that out of 27 virulence genes described and analyzed in the virulent tick transmitted strain, only five were fully identified in the attenuated laboratory strain. In all cases, the identity and coverture of the identified genes of the wildtype strain were higher than those of the laboratory strain. This finding is putatively associated with the continuous partial loss of virulence genes in the laboratory strain after several passages of the parasite population under optimal in vitro growth conditions. The loss of virulence factors might be reflected in the absence of symptoms of the disease in cattle inoculated with the attenuated strain despite the presence of infection in the bovine host cells.