Oral Bait Immunization of Eurasian Wild Boar (Sus scrofa) Against African Swine Fever with "ASFV-G-ΔI177L": Bait Performance, Immunogenicity, and Environmental Monitoring.

Background/

Objectives

African swine fever is currently the most devastating viral disease affecting domestic and wild suids, causing major economic losses and severe impacts on natural populations. Oral immunization could become an important tool to control the panzootic and support wild pig conservation. However, this requires safe and effective vaccines, baits accepted by target species, and vaccine reservoirs that reliably release the vaccine during bait intake while maintaining vaccine integrity.

Methods

We evaluated different bait types and vaccine containers in four wild Suiformes species, including Eurasian wild boar. In the same wild boar, we assessed oral vaccination with the live attenuated vaccine candidate "ASFV-G-ΔI177L". Environmental monitoring approaches were applied to detect potential virus shedding, and vaccine immunogenicity and dissemination were evaluated. Vaccine stability was tested in vitro in two container types under different temperature conditions.

Results

Bait uptake and container performance varied between manufacturers and among species. Environmental samples were largely negative for vaccine virus genome under controlled laboratory conditions, with only a few positive cotton ropes (0.43% of all samples). After oral bait vaccination, 45% (9/20) of wild boar seroconverted, with a higher proportion in animals receiving the vaccine in the slightly less attractive bait (gelatine-based). Vaccine virus dissemination was limited to a small number of organs, including gastrohepatic and mandibular lymph nodes.

Conclusions

Our findings demonstrate that wild pigs can be vaccinated orally with "ASFV-G-ΔI177L" while virus shedding appears minimal. Although the tested baits show potential for multiple target species, baits and containers require optimization. Environmental monitoring methods also need refinement for field application.