Foot and Mouth Disease Challenges and Solutions

Abstract

This study was conducted to investigate an outbreak of foot-and-mouth disease (FMD) in a vaccinated dairy herd (n = 4,145) and to identify the associated risk factors. Foot-and-mouth disease virus (FMDV) A Asia Iran-05 and SAT2 Libya 12-like viral RNAs were detected in clinical samples. Our data indicates that the outbreak occurred due to introduction of a field virus into cattle with minimal matching protective immune response. Previous vaccination with a multivalent vaccine did not prevent replication of a field virus that is an antigenic match to one of the vaccine seed viruses; with subsequent development of a mixed infection. The total cumulative incidence for the 31-day follow up period was 49.8% and the total mortality rate was 0.8%. The total incidence rate was 21 cases/1,000 cows/day, with confidence interval (CI) 20.32, 22.15. Analysis of epidemiological data revealed that lactation is the primary factor in disease development and mortalities in dairy herds (P < 0.005), possibly due to increased frequency of exposure and higher virus loads. Within this group, cows with 1 parity are more vulnerable in terms of disease development (relative risk 1.2, CI 1.121, 1.285) but not mortalities (P = 0.359). Correlations between FMD development and age should only be considered in the context of the reproductive state. Our analysis revealed that a reduction of the overall disease impact can be achieved by reduction of virus burdens in farms during outbreaks.