P6-4 In vivo assessment of Babesia bigemina vaccine strain throughout comparison against the virulent parental strain

PERTILE CARLA; FARBER MD; SARMIENTO, NESTOR

Simposio; 14th International Symposium on Ticks and Tick-borne Diseases; 2021

German Society for Parasitology

Live attenuated vaccines are used as control measure for bovine babesiosis in Argentina. Our goal was to statistically validate the phenotype of the B. bigemina vaccine strain BbiM1A, in comparison to the parental pathogenic strain BbiM1P. We selected 30 healthy steers, 36-48 months old, tested as negative for hemoparasites and free from Rhipicephalus microplus. The steers were randomly drawn and assigned into 3 groups (n=10/group). Two groups were inoculated subcutaneously, group 1 (G1) received 107 of BbiM1A. Group 2 (G2) received 107 of BbiM1P, and group (G3) was the negative control. Bovines were daily monitored and the parasiticidal treatment (Imidocarb) of any affected animal was based on the criteria of a drop of more than 50% in PCV, rise of rectal temperature >42°C and/or hemoglobinuria. Blood samples were collected with anticoagulant each day for PCV determination and DNA extraction for parasite detection using specific B. bigemina in house PCR assay. Forty five days after the immunization, G1 and G3 were challenged with a subcutaneous injection of 107 with virulent heterologous strain (BbiM2P). Statistical analysis were carried out using InfoStat, with a 95% confidence level. All animals (G1 and G2) B. bigemina positive results in thin blood smear since the sixth day post-inoculation. All steers from G2, required parasiticidal treatment in the seventh day after inoculation, none of the steers of G1 needed treatment. The P values between variables among G1 and G2 were