Dynamic of the natural infection by Anaplasma marginale in Holstein cows and calves in the Londrina region, North of Paraná State, Brazil

Abstract

The dynamic of the infection by Anaplasma marginale in Holstein cows and calves was studied in two dairy farms (A and B) in the Londrina region, North of Paraná. In the farm A the cows were maintained in the tie-stall system and, the calves in collective stall; in the farm B, the cows stayed in freestall system and the calves in individual cages. Every 15 days, blood samples were collected from the dams 45 days before parturition until 60 days post partum, and from their calves at birth until 240 days of age. Tick burden counting was also performed on dams and calves twice a month. Percentage of infected erythrocytes was established by Giemsa-stained smears. Blood and sera samples were examined by Polimerase Chain Reaction (PCR) and competitive Enzime-Linked Immunosorbent Assay (cELISA), respectively. In the cows, the anti-A. marginale antibody levels decreased close to the parturition, showing an adverse behavior among the farms. In the farm A the levels of antibodies increased between 30 and 60 days after the parturition and, in farm B the antibodies stayed in low levels during the accompaniment period of the cows. The anti-A. marginale antibody levels of the calves of the farm A, that were not high in the day of the birth, decreased more until 45 days post parturition and it increased again starting from 60 days, with maximum pick to the 105 days. In the farm B, where the calves presented higher levels of antibodies at the birth day, there was a slower decrease of the antibody levels, reaching the lowest point to the 75 days post parturition and it increased again more tardily, to the 165 days of age. The dams and calves in both farms were exposure to cattle tick Boophilus microplus during almost all period of accompaniment and they showed rickettsemia ranging from 0 to 1%. In conclusion, A. marginale infection after birth was more influenced by maternal antibody levels than tick burden; the differences between animals handling influenced the antibody levels of the dams and calves, and during the natural infection period of the calves; tick burden did not influence the rickettsemia in the studied farms.