Application of needle-free injection technology for foot and mouth disease vaccination via intradermal route
Authors:   , Wataradee Sirirat 
Published: September 2023

Foot and mouth disease (FMD) is an endemic disease in Thailand and caused severe economic loses. In order to prevent and control disease, the vaccination program is routinely administered for 2-3 times a year via subcutaneous route (SC). Even though, the vaccination is performed regularly, the outbreaks have often reported. The outbreaks occur due to the failure of number of immunity animal in population or herd immunity. The limitation of vaccine distribution to all animal population and difficulty of cattle restraint are forcible several farmers to failing to vaccinate their animals. Based on previous studies, the intradermal route (ID) can induce an efficient immune response with a lower dose than the SC route. Recently, the automatic needle-free intradermal vaccination has been applied as an alternative vaccinating method in dairy cows. The automatic needle-free intradermal vaccination offers the rapid and practical vaccine administration. Therefore, this study aims to compare the immune response between different routes of FMD vaccine administration and to optimize dose of ID vaccine. The conducted study used 40 calves and 40 heifers with inactivated FMD trivalent (O, A and Asia-1) vaccine in which produced locally by department of livestock development (DLD). The calves were allocated into seven groups of five calves per group (except 10 in group II) and vaccinated as group I: ID injected placebo (1 mL  normal saline), group II: SC vaccinated with 2 mL, group III: ID vaccinated via automatic needle-free device with 1 mL, groups IV-VII: ID vaccinated with 0.25 mL, 0.5 mL, 1 mL and 2 mL, respectively. Additionally, heifers were divided into four group of ten animals each. Group I 2 mL SC vaccination, group II 2 mL SC vaccination via automatic needle-free device with 2 mL, group III 1 mL vaccination and group IV 1 mL ID vaccination via automatic needle-free device. Calves were vaccinated twice (day 0 and day 14), while heifers were vaccinated only once with trivalent FMDV vaccine. Blood samples were collected from 0 to 120 days post-vaccination (dpv) to determine the immune response by viral neutralization test (VNT). To check status of FMD infection in experimental animal, the level of antibody against non-structural protein of virus (NSP) was measured by PrioCHECK FMDV NS ELISA tests. The result found that the 98 selected samples from 25 calves were found sero-negative for NSP antibodies. The highest average NAT against serotype O on 7 dpv was group VI (ID 1) followed by group IV (ID 0.25), while the highest average against serotype Asia-1 NAT on 7 dpv was group IV (ID 0.25) followed by group VI (ID 1). The levels of a proportion of protective levels against serotype O in calves was mostly lower than 40%. However, the result of the heifers found that the highest average NAT against serotype O on 7 dpv was mostly higher than 80% of the proportion of protective levels with no significant among groups. The results reveal that mostly NAT values in calves were low in which the NAT values from ID via automatic needle-free (group III) did not differ from SC (group II). Since the inactivated FMD vaccine has stimulated the low immune response with a short duration in protection, therefore, the vaccination in calves should be intense boosted. The results in heifers illustrated that automatic needle-free device via ID 1 mL can be a substitute for the SC. In order to reduce dosage of vaccine, the application of ID via an automatic needle-free device can be considered as the alternative for FMD vaccination in Thai dairy cattle.