Potency of a commercial inactivated trivalent foot-and-mouth disease vaccine in local goats of the Diyala Governorate, Iraq

Foot-and-Mouth Disease remains one of the most economically devastating infections affecting livestock producers globally. This study evaluated the immunogenicity and field efficacy of a commercial inactivated trivalent vaccine containing serotypes O, A, and Asia-1 in the local goat population of the Diyala Governorate, Iraq, focusing on assessing how host sex and pregnancy status modulate the resulting humoral immune response. A total of 178 clinically healthy local breed goats, comprising 100 females and 78 males aged between 7 and 36 months, were immunized with a single 1 mL dose administered subcutaneously. Paired blood samples were collected immediately before vaccination (Day 0) and at Day 28 post-vaccination to capture peak antibody synthesis. Serological analysis was performed using a commercial solid-phase competitive enzyme-linked immunosorbent assay kit, with antibody levels expressed as percentage inhibition, where a threshold of greater than or equal to 50 % was defined as protective immunity. Evaluation of baseline samples revealed a pre-vaccination seropositivity rate of 15.2 % (27/178), confirming that the virus is endemic to the region. Following immunization, the overall protective seropositivity rate increased significantly to 89.3 % (159/178) by Day 28 (p<0.001), and the mean percentage inhibition values more than doubled across all three viral strains. Host sex exerted no statistically significant influence on vaccine responsiveness (p=0.541), yielding comparable seropositivity rates of 87.2 % for male and 90.8 % for female cohorts. Conversely, pregnancy status imposed a substantial physiological limitation on vaccine-induced immunogenicity. Pregnant goats exhibited a significantly lower protective seropositivity rate of 82.1 % compared to 97.3 % in non-pregnant animals (p=0.026). Furthermore, gestation significantly suppressed antibody synthesis levels for serotypes O (p=0.001) and Asia-1 (p=0.002). In conclusion, while the commercial trivalent vaccine is safe and highly potent, pregnancy-induced immunosuppression significantly reduces its protective efficacy. These findings suggest that small ruminants must be integrated into national control programs, and vaccination campaigns should be strategically timed during non-pregnant phases, such as the early dry period or prior to the breeding season, to optimize herd immunity.