Duration of the antibody response following intradermal administration of a quarter-dose oil adjuvant foot-and-mouth disease vaccine in sheep.

Foot-and-mouth disease is a significant viral disease affecting cloven-hoofed domestic and wild animals. One of the most effective measures for combating this disease is vaccination. However, sheep are often excluded from vaccination campaigns because of vaccine shortages. Intradermal vaccination can significantly reduce the quantity of antigens and adjuvants required, thereby increasing vaccine availability. Although numerous experimental studies have been conducted on the intradermal administration of the FMD vaccine, no such studies have been conducted on sheep, and the duration of antibody response for this species remains unclear. Inactivated antigens for foot-and-mouth disease, including O/Panasia-II, A/IRN-05, A/ASIA/G-VII, and ASIA1/Sindh-08, were formulated using ictyolane 18 and ictyolane 30 adjuvants to prepare water-in-oil-in-water and microemulsions. Forty-five Merino sheep were randomly divided into four groups of 10 animals each, with one unvaccinated group containing five animals. One mL of vaccine (> 3PD₅₀) was administered intramuscularly to the intramuscular groups (IM18 and IM30), whereas 1/4 mL was administered intradermally to intradermal groups (ID18 and ID30). A booster dose was administered to all groups on day 28. Blood samples were collected from the sheep at various intervals: days 0, 7, 14, 28, 58, 86, 118, 151, 179, 211, 241, 270, 302, 338, and 361. Serum antibody levels were determined using VNT and LPB-ELISA. No difference was observed between the reduced-dose intradermal and full-dose intramuscular administration of Ictyolane 18 (ICT18) vaccine formulation (p > 0.05) in terms of antibody level and duration in sheep. It has been observed that the Ictyolane 18 formulations generally stimulate a higher antibody response than the Ictyolane 30 formulations.