Experimental Immunogenicity and Multi-Region Field Performance of a Briquette-Formulated Oral Rabies Vaccine Bait in Kazakhstan

Wildlife reservoirs sustain rabies transmission despite vaccination of domestic animals, highlighting the need for oral rabies vaccination strategies adapted to contrasting ecological settings. We conducted a pilot multi-region field evaluation of a locally developed briquette-formulated oral rabies vaccine bait at purposively selected sites in four regions of Kazakhstan during 2025–2026. Overall, 9256 baits were deployed, including 4556 placed manually and 4700 distributed by aircraft. Among the manually monitored baits, apparent uptake was 57.2% (2604/4556) and ranged from 11.3% to 75.3% among region-campaign groups. Recovered baits retained their structural integrity following a controlled aerial test drop. Tetracycline fluorescence was detected in seven of ten free-ranging foxes, and six had rabies virus-neutralising antibody titres of ≥0.5 IU/mL. Following controlled oral administration of a single bait, all six initially seronegative captive red foxes and four of five captive raccoons met the predefined seroconversion criterion. These findings support the operational field feasibility of the briquette-formulated bait across contrasting selected landscapes and demonstrate oral immunogenicity under controlled conditions. The observed variation in apparent uptake indicates that bait distribution strategies should be adapted to local wildlife ecology and deployment conditions.