Immune Response In Neospora caninum Seropositive Calves Experimentally Suppressed With Dexametasone

IDÁRRAGA S; LEUNDA MR; VERNA AE; PEREYRA S; HECKER Y; NEUMAN R; CANO D; CAMPERO CM; ODEON AC; MOORE DP

Conferencia; 23rd. International Conference of the World Association for the Advancement of Veterinary Parasitology in Buenos Aires; 2011

The aim of this study was to characterize the immune response to Neospora caninum in seropositive calves experimentally immunosuppressed by administration of dexamethasone (Dx). A total of 16 beef breed cattle 8-10 months of age were used divided into 4 experimental groups: Group A: 4 seropositive animals treated with Dx; Group B: 4 seropositive animals treated with placebo; Group C: 4 seronegative animals treated with Dx; and Group D: 4 seronegative animals treated with placebo. Dx treatment consisted of a dose of 0.1 mg/kg/day intramuscularly for 5 consecutive days. Clinical examination including rectal temperature was performed at one day interval. Blood samples with heparin were obtained for counting leukocytes and characterizing its formulae. Serum was obtained weekly to evaluate total IgG by indirect flourecent antibody test. Leukocytes were separated from whole blood to asses PCR. Not clinical sings were observed trough the experiment time, however few animals from all experimental groups had fever during a short period of time. Leukocytopenia was recorded in all animals receiving Dx (Groups A and C) at the 3rd and 14th day after giving the first dose. Similarly, neutrophilia and lymphopenia was recorded at the 3rd and 14th days, respectively. Interestingly, there were two peaks of IgG titers (mean reciprocal antibody titers: ≥500) in animals from Group A compared with those in animals in Group B (mean reciprocal antibody titers: =275). All animals from Groups C and D remained seronegative trough the experimental period. Two weeks after giving 1st dose of Dx all four calves in Group A had PCR positive results on the leukocytes. Parasitemia and seroconversion was induced in N. caninum seropositive calves after experimental immunosuppression by administration of dexamethasone.