Development and characterization of a modified Komarov's bullet for ballistic delivery of live Brucella abortus strains 82 and 19 to cattle and bison

In this study a modified Komarov's bullet was developed to remotely deliver live brucellosis vaccines (Brucella abortus 82 and Brucella abortus 19). After modification, the bullet payload could carry the desired dose (1011 CFU) of vaccine. As the bullet components were toxic to the live bacteria, a special protective coating was developed for the bullet inner surface that maintained vaccine viability. Vaccine viability was not influenced by ballistic delivery and the characteristics of the modified bullet allowed accurate delivery at distances of 100 m. Intramuscular ballistic delivery of the modified Komarov's bullet into live cattle and bison was not associated with detrimental clinical effects. The modified bullet penetrated approximately 3–5.5 cm into muscular tissue. At necropsy after 63 days, recovered bullets were deformed or broken into multiple pieces but were not associated with adverse lesions. Ballistically delivered vaccines of both strains induced high immunological responses in cattle and bison confirmed by serological, immunological tests, PCR and pathomorphological examination of internal organs.Therefore, the clinical and ballistic characteristics of the modified Komarov's bullet, in addition to its ability to be delivered at distances of 100 m, demonstrate its usefulness for use in remotely delivering brucellosis vaccines to free-ranging animals. A high immune response induced by ballistically delivered Brucella abortus 82 vaccine proves that this vaccine strain can be used for vaccination of free-ranging animals.