Estudo de infecção por Babesia Bigemina em bovino de corte e em carrapato

Abstract

Babesia bigemina infections were investigated in four genetic groups of beef cattle and in Rhipicephalus (Boophilus) microplus engorged female ticks. Blood samples and engorged female ticks were collected from 15 cows and 15 calves of each of the following genetic groups: Nelore (NE), ½ Angus + ½ Nelore (NA), ½ Canchim + ½ Nelore (CN) and ½ Simmental + ½ Nelore (SN). Microscopic examination of blood smears and tick hemolymph revealed that merozoites of B. bigemina (6/60 - 10%) as well as kinetes of Babesia spp. (9/549 - 1,6%) were only detected in samples (blood and ticks, respectively) collected from calves. Polimerase chain reaction (PCR) based methods using primers for specific detection of B. bigemina revealed 100% of infection in both calves and cows, regardless the genetic group. Tick infection was detected by nested PCR amplifications showing that the frequency of B. bigemina was higher (P < 0.01) in female ticks collected from calves (134/ 549 - 24,4%) than in those collected from cows (52/553 - 9,4%). The frequency of B. bigemina was similar in ticks collected from animals of the four genetic groups (P > 0.05). The larval hatching rates were significantly lower for engorged females ticks with positive reaction for B. bigemina (53.5%) than those with negative reaction (65.9%). There was no difference between larval hatching rate of females ticks collected from the four genetic groups.