Physical Factors Affecting in Vitro Replication of Foot and Mouth Disease Virus (Serotype 'O')

Effect of physical factors (temperature, pH and UV light) on replicating ability of “O” type of Foot and Mouth Disease (FMD) virus on Baby Hamster Kidney (BHK) cell line was determined. The freshly grown FMD virus containing 106 units of tissue culture infective dose (TCID50) was divided into aliquots. Each of the 9 virus aliquots was exposed to 37, 57 or 77C for 15, 30 or 45 minutes, respectively. Each of the 5 virus aliquots was mixed with MEM-199 maintenance medium having pH 3, 5, 7, 9, or 11. Similarly, each of the 3 aliquots having 1 mm depth of the medium was exposed to ultraviolet light (252.7 nm wavelength: one foot distance) for 15, 30 or 45 minutes. Each of the virus aliquot exposed to either of the temperature, pH or ultraviolet light (UV) for either of the interaction time was inoculated to 8 wells of the 96-well cell culture plate containing complete monolayer of BHK cell line. One row of 8 wells served as virus control and other row of 8 wells served as control for monolayer of the BHK-21 cell line. The plates were incubated at 37°C for 48 hours. It was observed that temperature of 57 and 77C inactivated the virus within 15 minutes. The virus when admixed in the MEM-199 maintenance medium having pH 3, 5, 9 or 11, of the medium inactivated the virus while pH 7 did not show any detrimental effect on its survival. The ultraviolet light for 15, 30 or 45 minutes showed undetectable effect on survival of the virus as either of the virus aliquot exposed to the UV light for either of the interaction time showed cytopathogenic effects (CPE). It was concluded that the temperature of 57°C or higher for 15 minutes, acidic pH (below 5) or basic pH (more than 9) may inactivate the FMD virus.