Vimis in Bovine Skin

GAILIUNAS, PETER (Plum Island Animal Disease Laboratory, Greenport, N. Y.), AND GEORGE E. CoTTRAL. Presence and persistence of foot-and-mouth disease virus in bovine skin. J. Bacteriol. 91:2333-2338. 1966. -This study established that the seven known antigenic types of foot-and-mouth disease virus (FMDV) have consistent affinity to all areas of bovine skin, even though gross cutaneous lesions usually are found only in the pedal area. Considerable amounts of FMDV were present in skin of 13 different body areas, irrespective of the presence of hair. All skin specimens from the trunk of 50 experimentally infected steers, necropsied from 12 hr to 7 days postinoculation (DPI), contained FMDV in the dermal and epidermal tissues. In skins of some steers, FMDV persisted for as long as 5 days after cessation of viremia. The highest average virus titer, 103 6 plaque-forming units (PFU) per g of skin, was found at 2 DPI. Some areas of the trunk and extremities had titers of approximately 1050 PFU per g of skin. Characteristic gross lesions were not observed in sampling areas. The present observations have epizootiological importance for hides offered in international trade, because FMDV localized intracutaneously is more difficult to inactivate than virus adhering to hide surfaces. This study was conducted to obtain basic information on the occurrence of foot-and-mouth disease virus (FMDV) in bovine skin not affected by characteristic gross lesions. Although the hazards of disseminating FMDV through hides of cattle were recognized nearly 40 years ago (13), reports concerning occurrence of FMDV in various skin areas of natural hosts are not available. The Fourth Progress Report of the British Foot-and-Mouth Disease Research Committee (6) described the detection of FMDV in a salted hide stored at "outside temperature" for 46 days, but failed to show that infectivity of the specimens tested was not due to surface contamination. The consensus of published opinions seems to be that FMDV has no affinity for normal hairy skin (5, 12). The dissemination of FMDV through hides was attributed to contamination of their surfaces with viremic blood or other infectious materials (15). According to Belin (3), FMDV propagates in all deep epithelial layers which are in an active state of regeneration, and the vesicles develop wherever superficial layers of the skin do not obstruct their eruption, like interdigital spaces, mouth, and inner thigh of cattle with thin skin. Belin further stated that the remainder of the cutaneous surface is free of evidence of the development of visible lesions. Localization of the FMDV, after the viremic stage, was believed to be in the epithelial tissues (11). Platt (14) pointed out that the localization of FMDV lesions is strictly limited to the sites of predilection, and that their extension to the hairy skin of the legs rarely occurs. This report presents observations on the occurrence, persistence, and distribution of FMDV throughout various areas of bovine skin. MATERIALS AND METHODS Viruses. Strains representing all seven known types of FMDV were used. Four were Argentine field strains, A-1, 0-2,0-9, and C-3, and one was a European field strain from The Netherlands, 0-Mulder. In addition, one Asian and three African strains were used, Asia-i PAK-1, SAT-1, RV-11, SAT-2 RHO-1, and SAT-3 RV-7. All viruses were passed only in cattle, and were stored at -50 C. Further history of the virus strains, passage levels used, and storage conditions have been reported (4). Cattle. Grade Hereford steers and heifers, 16 to 24 months old, weighing from 270 to 320 kg, were used as a source of skin samples and also for confirmation