Evaluation of an ELISA to detect rabies antibodies in orally vaccinated foxes and raccoon dogs sampled in the field.

The assessment of the efficacy of oral vaccination in wildlife is based on detection in the teeth of a biomarker (tetracycline) which is incorporated in the vaccine bait, and the quantification of rabies antibodies. A blocking ELISA was evaluated and compared with the FAVN test and a validated in-house ELISA, using sera from foxes and raccoon dogs collected following oral vaccination campaigns in France and Estonia. Specificity reached 100% in sera from naïve animals. A high concordance (95%) was observed between the BioPro ELISA and the FAVN test, which was similar in sera from red foxes and raccoon dogs. Concordance between the BioPro ELISA and the in-house ELISA reached 96.5% for sera from red foxes. The agreement with tetracycline results was excellent in the fox for both the BioPro ELISA (95.9%) and the FAVN test (91.8%). Concordance was slightly lower in the raccoon dog, with a value of 82.8% for the BioPro ELISA and 78.4% for the FAVN test. Rabies antibodies were detected with the BioPro ELISA in animals vaccinated with different types of vaccines and in highly haemolysed sera. The BioPro ELISA is a valuable test to assess the efficacy of oral vaccination in foxes and raccoon dogs.