1a Department of Microbiology and Immunology , University of Otago , P.O. Box 56, Dunedin , New Zealand.
An enzyme-linked immunosorbent assay (ELISA) was developed to estimate levels of IgY antibody against the bacterium Erysipelothrix rhusiopathiae in serum samples collected from the critically endangered kakapo (Strigops habroptilus, Psittaciformes, Aves) before and after vaccination against this bacterium. Relative IgYantibody titres in pre-vaccination serum samples (n = 71 individual kakapo) were normally distributed with the exception of four outliers which displayed low IgY levels. Notably all four low IgY samples were collected from fledglings 3 - 6 months old. Pre-vaccination serum samples from nine nestlings <3 months old, seven of which were hatched in incubators and had no contact with either adult kakapo or their natural environment (e.g. soil), were found to have relatively high IgY levels, suggesting transfer of maternal IgY molecules to fledglings via the yolk. IgY levels in pre-vaccination serum samples from seven kakapo aged 25 - 30 months were also relatively high, suggesting that most kakapo naturally acquire anti- E.rhusiopathiae IgYs within their first 2 years. There was no evidence that vaccination increased the kakapo population's mean anti-E.rhusiopathiaeIgY levels. However, there was a significant negative relationship between an individual bird's pre-vaccinationIgY level and any subsequent increase following vaccination, suggesting that vaccination may only raise theIgY levels of birds with relatively low pre-vaccination IgY levels. A statistical model of the relationship between 'death from erysipelas' and sex, age and transfer from one to island sanctuary to another found that only transfer was significantly associated with death from erysipelas.