First Report on the Efficiency of Oral Vaccination of Foxes against Rabies in Serbia

Rabies is one of the oldest known zoonotic diseases that has significant impact on public health, but still remains neglected in Serbia. Rabies virus can infect humans and other mammals and causes inflammation of the brain associated with encephalomyelitis and neurological symptoms. In 2010, Veterinary Directorate (national Competent Authority for animal health in Serbia) has started multi-annual project of oral rabies vaccination of foxes and other wild carnivores (e.g. jackals), as support of long-term programme of eradication of rabies in Serbia, co-funded by EU (financed by Instrument for Pre-Accession Assistance). Monitoring of the effectiveness of oral vaccination campaigns has been carried out in continuation from 2011 and was based on: (i) post-mortem laboratory examination of brain tissue of target animals (foxes, jackals and other carnivores) by fluorescent antibody test (FAT), (ii) detection of antibodies against rabies virus in serum samples by ELISA and (iii) detection of tetracycline biomarker in the mandibles for the evaluation of vaccine bait uptake. From September 2011 to May 2014, the total number of 4943 brain tissue samples, 4241 sera and 4971 mandibles were analysed. Confirmed rabies-positive brains decreased from 10 in 2011/2012 to 6 in 2012/2013 and eventually to 1 positive case in 2013/2014. The sero-conversion rate increased from 10.48% (133/1269) in 2011/2012 to 20.11% (362/1800) in 2012/2013 and 42.23% (495/1172) in 2013/2014. Along with the sero-conversion, the number of detected tetracycline-positive mandibles demonstrated an increasing tendency in the same period, being 49.67% (682/1373) in 2011/2012, 62.60% (1294/2067) in 2012/2013 and 90.33% (1383/1531) in the monitoring programme carried out in 2013/2014. Presented results confirmed that ORV of foxes and other wildlife in Serbia against rabies was successful and characterized by steady increase of vaccine baits uptake and immunization of animals.