Dynamics of Neospora caninum transmission in naturally infected sheep under semiarid conditions

Abstract

This study longitudinally assessed the serological profile of N. caninum occurrence among female lambs in the first year of life to determine the main age at which primary infection occurred under semiarid conditions. Blood samples were collected from 53 pregnant ewes from farms in Paraíba state, Brazil in the month before giving birth, and their 59 female offspring were sampled monthly up to one year of age. The indirect fluorescence antibody test was used, with a cutoff point of 1:50. Among the pregnant ewes, 26.4% (14/53; CI = 14.1%−38.7%) were positive. Among the offspring, 61% (36/59; CI = 48.2%−73.8%) of the lambs monitored were positive for anti-N. caninum antibodies in at least one of the 12 months of evaluation. Transient antibody production was observed for a short period after seroconversion. Among the offspring of positive mothers, a smaller oscillation in the production of antibodies was observed over the period. There was a correlation between the antibody titers of mothers and offspring in the first month of life (r = 0.59; P < 0.0001). It was also observed that 76.7% (23/30) of post-natal infections occurred before reproductive age (six months) was reached (P = 0.0035). It was concluded that in most lambs, primary infection occurs up to reproductive age. Furthermore, infection by N. caninum occurs throughout the year in this semiarid environment, giving rise to transitory production of antibodies for this protozoon. This emphasizes the importance of longitudinal studies.