Indirect estimation of porcine parvovirus maternal immunity decay in free-living wild boar (Sus scrofa) piglets by capture–recapture data

Linear mixed regression and logspline density estimation were performed to estimate the survival curve and half life of passively acquired antibodies against porcine parvovirus (PPV) in 44 wild boar piglets captured in the Northern Apennines, Italy. One piglet had no detectable maternal antibodies at 2.5 months post partum and no antibodies were detected in any of the remaining piglets by 4 months of age. Fitted survival curves indicated that maternal antibodies were undetectable from 2.5 to 6 months of age, with a median value at 3 months and a low probability of persistent maternal antibodies after 4 months of age. The estimated half life was 23 days (95% confidence interval 22–26 days). The results agree with previous data for decay of maternally acquired antibodies against PPV in the domestic pig and indicate the value of capture–recapture analysis for the estimation of infection parameters in free-living animals.