Foot-and-mouth disease and vesicular stomatitis a comparative microscopical study

Abstract

The purpose of this paper is to describe and demonstrate the microscopical appearances, and the differences that have been observed in infective material obtained from primary vesicles, resulting from the inoculation of suitable susceptible animals with foot-and-mouth disease and vesicular stomatitis. The pathological changes -which occur in foot-and-mouth disease have been intensively studied by a number of workers. Of the established facts, one or two may perhaps be recalled with advantage in relation to the studies to be described. The primary vesicle is the chief interest since it has been the main source of the material studied, but changes occurring in distant parts of the body are not without significance. In briefest outline this is what is usually observed in the guinea-pig. During the 24 hr. immediately following inoculation of the hindfoot, local focal changes appear within the epithelial layer; steadily enlarging groups of epithelial cells degenerate and disintegrate as vesicles filled with clear fluid appear, increase in size and coalesce with neighbouring vesicles. At this stage both the vesicular fluid and the vesicular epithelium are highly infective. The blood becomes infective quite early in the disease and by the end of the second day following inoculation secondary vesicles are appearing in the epithelium of the tongue and of the soles of the forefeet. Sometimes the disease progresses till death occurs, but usually repair processes soon begin, the blood becomes non-infective, and the walls and fluid of the primary vesicles rapidly decline in infectivity. By the fourth or fifth day all the vesicles are healing. By about the end of the third week desquamation of the damaged epithelium is complete and the skin has returned to normal.