Kinetics of maternal immunity against abies in fox cubs (Vulpes vulpes)

In previous experiments, it was demonstrated that maternal antibodies (maAb) against rabies in foxes (Vulpes vulpes) were transfered from the vixen to her offspring. However, data was lacking from cubs during the first three weeks post partum. Therefore, this complementary study was initiated. Methods: Blood samples ( n=281) were collected from 64 cubs ( 3 to 43 days old) whelped by 19 rabies-immune captive-bred vixens. Se a was collected up to six times from each cub. The samples we e analysed by a fluorescence focus inhibition technique (RFFIT), and ant body titres (nAb) were expressed in IU/ml. The obtained data was pooled with previous data sets. Subsequently, a total of 499 serum samples from 249 cubs whelped by 54 ab rabies-immune vixens were fitted to a non-linear regression model. Results: The disappearance rate of maAb was independent of the vixens' nAb-titre. The maAb-titre of the cubs deceased exponent ally with age and the half-life of the maAb was est mated to be 9.34 days. However, maAb of offspring whelped by vixens with high nAb-titres can be detected longer in RFFIT then those of offspring whelped by vixens with relatively low nAb-titres. At a mean critical age of about 23 days post partum, maAb could no longer be distinguished from unspecific reactions in RFFIT depending on the amount of maAb transferred by the mother. Conclusions: The amount of maAb cubs receive is directly proportional to the titre of the vixen and decreases exponent ally with age below detectable levels in seroneutralisation tests at a relatively early age