Abstract
Babesiosis is an economically important infectious disease affecting cattle worldwide. In order to longitudinally evaluate the humoral immune response against Babesia bovis and the merozoite surface antigen diversity of B. bovis among naturally infected calves in Taiaçu, Brazil, serum and DNA samples from 15 calves were obtained quarterly, from their birth to 12 months of age. Anti-B. bovis IgG antibodies were detected by means of the indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA). The polymerase chain reaction (PCR) was used to investigate the genetic diversity of B. bovis, based on the genes that encode merozoite surface antigens (MSA-1, MSA-2b and MSA-2c). The serological results demonstrated that up to six months of age, all the calves developed active immunity against B. bovis. Among the 75 DNA samples evaluated, 2, 4 and 5 sequences of the genes msa-1, msa-2b and msa-2c were obtained. The present study demonstrated that the msa-1 and msa-2b genes sequences amplified from blood DNA of calves positive to B. bovis from Taiaçu were genetically distinct, and that msa-2c was conserved. All animals were serologically positive to ELISA and IFAT, which used full repertoire of parasite antigens in despite of the genetic diversity of MSAs.
Highlights
Bovine babesiosis is an economically important hemoparasitosis affecting cattle worldwide (MTSHALI & MTSHALI, 2013)
At the second sampling time, three calves (20%) were seropositive for B. bovis and nine calves (60%) for B. bigemina according to indirect fluorescent antibody test (IFAT); all the calves presented antibodies levels for B. bovis and B. bigemina that were below the enzyme-linked immunosorbent assay (ELISA) cutoff value at that time
At six months of age, 93.3% and 100% of the calves were seropositive for B. bovis and 100% for B. bigemina according to IFAT and ELISA, respectively
Summary
Bovine babesiosis is an economically important hemoparasitosis affecting cattle worldwide (MTSHALI & MTSHALI, 2013). It is transmitted by ticks of the family Ixodidae, especially those belonging to the subgenus Rhipicephalus (Boophilus) spp. In Brazil, bovine babesiosis is caused by the apicomplexan intraerythrocytic protozoa parasites Babesia bovis and B. bigemina, which are agents of huge economic importance in tropical and subtropical regions (JULIANO et al, 2007; SIVAKUMAR et al, 2013). It has been proposed that members of the VMSA family play key roles in the initial attachment of merozoites and sporozoites in the erythrocyte host cell during invasion into intermediate hosts (MOSQUEDA et al, 2002; YOKOYAMA et al, 2006)
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