Monolayer cultures of Vero cells grown on 24-well plates were infected in duplicate with ten-fold serial dilutions of tissue homogenate, and the cells were overlayed with OptiMEM (Invitrogen) supplemented with 1% methylcellulose, 5% FBS, 2.5 µg/ml amphotericin B, and 20 µg/ml ciprofloxicin. Five days after infection the overlay was removed and cells were washed twice with PBS. The cells were fixed and stained for 10 minutes with crystal violet solution, virus plaques were enumerated, and tissue titers were expressed as mean log 10 PFU/g tissue.