In vitro Adaptation, Molecular Characterization and Tissue Tropism of Foot-and-mouth Disease Virus in Guinea Pigs

Background: Foot-and-mouth disease is a highly contagious disease in cloven-footed animals. It is reported to be endemic in Pakistan. Methods: Molecular characterization of FMD virus field isolate was carried out, followed by an investigation of the tissue tropism in guinea pigs’ heart and respiratory organs. After calculating the biological titer of the virus and guinea pigs infectious dose50, the virus was injected into the hind metatarsal feet pads of 30 guinea pigs to study the pathogenesis of the disease at different day intervals from day 1 to 28. Result: Phylogenetic analysis showed that the isolate belonged to ME-SA topotype of serotype “O” with lineage Pan-Asia II. In pathological findings, hemorrhages and congestion in the heart and trachea and edema in the lungs were observed. Histopathological examination showed myocardial necrosis and tracheal epithelium sloughing along with bronchial edema. In Immunohistochemical studies, antigen load was detected in the heart, trachea and lungs up to 14 days post-inoculation. The study suggested that small experimental animals would be a better cost-effective replacement for large animals to study the pathogenesis of the disease as the virus did not change its behavior in these laboratory animals.