Improved stability and specificity of baits for oral administration of substances to wild boar.

Oral vaccination is one of the most effective interventions for disease control in wildlife. As a result of the recent global reemergence of African swine fever and ongoing classical swine fever and animal tuberculosis, oral vaccination of Eurasian wild boar (Sus scrofa) receives increased interest. Several baits for wild boar and feral pigs have been described, but developing more stable and personalized formulations is important. This paper proposes a new bait formulation primarily composed of corn flour, piglet feed, sugar, and honey as a binder to obtain improved elasticity. The bait consists of a matrix with no protective coats, has a hemispherical shape (ø 3.4 ×1.6 cm), and displays an anise aroma and blue color. The color and aroma did not affect bait choice by wild boar, while bait coloring contributed to avoid consumption by non-target species (corvids). Baits with the new formulation were significantly more resistant to humidity and high temperatures than previous versions. Simulations suggest that baits with the new formulation are elastic enough to resist impacts from a maximum altitude of 750 m. Thus, the new bait prototype solves several problems of previous bait formulations while keeping a format that can be selectively consumed by piglets and adult wild boar.

Assessment of African swine fever vaccine candidate ASFV-G-∆MGF in a reversion to virulence study.

African swine fever (ASF) has gained panzootic dimensions and commercial vaccines are still unavailable. Recently, a series of live attenuated vaccines has raised hope for an efficacious and safe vaccine, among them "ASFV-G-∆MGF". We tested the latter in an in vivo reversion to virulence study in accordance with International Cooperation on Harmonisation of Technical Requirements for Registration of Veterinary Medicinal Products guidelines. Upon forced animal passaging, a virus variant emerged that was associated with transient fever and an increased replication and shedding. However, all animals were healthy upon completion of the study and reversion to significant virulence was not observed. The genomic changes did not affect the recombination site but involved deletions and reorganizations in the terminal regions of the genome. Thus, our study underscores that in-depth safety characterization is needed for live ASF vaccines. For this particular candidate, additional studies should target long-term effects and transmission characteristics before thorough benefit-risk analysis can be carried out.

Taking a Promising Vaccine Candidate Further: Efficacy of ASFV-G-ΔMGF after Intramuscular Vaccination of Domestic Pigs and Oral Vaccination of Wild Boar.

African swine fever (ASF) is a pandemic threat to the global pig industry and wild suids. A safe and efficacious vaccine could monumentally assist in disease eradication. In the past years, promising live attenuated vaccine candidates emerged in proof-of-concept experiments, among which was "ASFV-G-∆MGF". In our study, we tested the vaccine candidate in three animal experiments intramuscularly in domestic pigs and orally in wild boar. Further, a macrophage-grown vaccine virus and a virus grown on permanent cells could be employed. Irrespective of the production system of the vaccine virus, a two-dose intramuscular immunization could induce close-to-sterile immunity with full clinical protection against challenge infection. After oral immunization, 50% of the vaccinees seroconverted and all responders were completely protected against subsequent challenge. All nonresponders developed ASF upon challenge with two acute lethal infections and two mild and transient courses. The latter results show a lower efficiency after oral administration that would have to be taken into consideration when designing vaccination-based control measures. Overall, our findings confirm that "ASFV-G-∆MGF" is a most promising vaccine candidate that could find its way into well-organized and controlled immunization campaigns. Further research is needed to characterize safety aspects and define possible improvements of oral efficiency.

Vaccination of horses with a recombinant modified vaccinia Ankara virus (MVA) expressing African horse sickness (AHS) virus major capsid protein VP2 provides complete clinical protection against challenge.

African horse sickness virus (AHSV) is an arthropod-borne pathogen that infects all species of equidae and causes high mortality in horses. Previously, a recombinant modified vaccinia Ankara (MVA) virus expressing the protein VP2 of AHSV serotype 4 was shown to induce virus neutralising antibodies in horses and protected interferon alpha receptor gene knock-out mice (IFNAR -/-) against virulent AHSV challenge. This study builds on the previous work, examining the protective efficacy of MVA-VP2 vaccination in the natural host of AHSV infection. A study group of 4 horses was vaccinated twice with a recombinant MVA virus expressing the major capsid protein (VP2) of AHSV serotype 9. Vaccinated animals and a control group of unvaccinated horses were then challenged with a virulent strain of AHSV-9. The vaccinated animals were completely protected against clinical disease and also against viraemia as measured by standard end-point dilution assays. In contrast, all control horses presented viraemia after challenge and succumbed to the infection. These results demonstrate the potential of recombinant MVA viruses expressing the outer capsid VP2 of AHSV as a protective vaccine against AHSV infection in the field.