Oral rabies vaccination of foxes with one or two delayed distributions of SAG2 baits during the spring

During the spring of 1997, various protocols of rabies vaccine bait (SAG2) distribution for foxes were compared: in the first test zone, a first distr ibution was organised at the end of April, followed by a second distributio n two weeks later; in the second test zone, there was a first distribution at the same period as fur the previous zone, followed by a second distribut ion four weeks later, at the end of May. In two control zones, a classical single bait distribution was organised during the same periods as Tot the s econd distribution in the respective test zones. No statistical differences were observed for adult foxes or fox cubs sampled in the test and control zones neither for baits uptake nor for seroconversion rare. However, seroco nversion rates observed in fox cubs population were significantly higher (P < 0.01) in areas vaccinated at the end of May (43 and 56 %) compared with those vaccinated at mid-May (24 and 20%). The vaccinal efficacy of baits wa s also significantly (P < 0.05) increased for the fox cubs in the areas vac cinated at the end of May (46 and 57%) compared with those vaccinated at mi d-May (24 and 25%). This increase in immunological response by fox cubs whe n vaccinating in late spring must be related to their development. In the e arly spring, fox cubs are generally too young, to have access to baits or t o be vaccinated when eating them. For most of these fox cubs, a second dist ribution will not constitute a booster. Therefore, in order to increase the efficient access of fox cubs to vaccine baits, Spring distribution of bait s should preferably be organised during May or June rather than in April.