Inactivation of an Indonesian isolate of foot-and-mouth disease virus using formaldehyde

Background and Aim: Foot-and-mouth disease (FMD) is a highly contagious viral disease that endangers livestock and the environment with significant economic consequences. This study aimed to validate the inactivation of the Indonesian isolate of foot-and-mouth disease virus (FMDV) with various formaldehyde concentration. Materials and Methods: The experiment started with FMDV being adapted on BHK-21 cells until cytopathic effects (CPE) appeared. The biological titer of the virus was determined using the 50% tissue culture infectious dose (TCID50) assay. The virus was inactivated by exposing the isolate to different formaldehyde (FA) concentrations (0.025%, 0.05%, 0.1%, and 0.2%) at 37°C for 24 h, and residual infectivity was assessed using CPE scoring of reinoculated BHK-21 cells. Results: 72 h post-inoculation, the virulence of the FMDV isolate was indicated by complete CPE on BHK-21 monolayer cells, with a TCID50 value of 109/mL; CPE scoring did not signify significant differences (p < 0.05) among 0.025%, 0.05%, 0.1%, 0.2% FA, and the negative control. All treatment groups showed significant differences (p < 0.05) from the positive control (C+). FA concentrations inactivated the FMDV isolate under the given conditions. 0.025% and 0.05% FA continued to display CPE through the third passage, while 0.2% FA did not significantly differ from 0.1% FA (p > 0.05). 0.1% FA is the optimal concentration for safely and effectively inactivating FMDV. Conclusion: All of the formaldehyde concentrations can completely inactivate the FMDV isolate, with the most optimal and safe concentration being 0.1%.