EXPERIMENTAL VESICULAR STOMATITIS IN SWINE - EFFECTS OF ROUTE OF INOCULATION AND STEROID TREATMENT

An enzootic focus of vesicular stomatitis virus New Jersey serotype (V SV-NJ) exists on Ossabaw Island, Georgia. Many questions regarding the epizootiology of this virus at this focus still exist, but evidence s uggests that the vector for this virus is a phlebotomine sand fly (Lut zomyia shannoni), with feral swine serving as a potential source of vi rus for the sand fly and for other swine via contact transmission. We conducted 2 experimental trials in domestic swine using VSV-NJ isolate d from a sand fly from Ossabaw Island to determine if route of inocula tion or immunosuppression via steroid administration affected the deve lopment of disease, viremia, viral shedding, or the neutralizing antib ody response. In a third trial, we studied the potential for contact t ransmission among swine using this isolate. Virus isolations were made from nasal cavity or palatine tonsil of the soft palate, and VSV-NJ n eutralizing antibodies developed when pigs were inoculated intradermal ly in the apex of the snout, ear, or coronary band, intravenously, int ranasally, or via scarification of the apex of the snout or coronary b and. Vesicles developed only in pigs inoculated in the apex of the sno ut or coronary band, and these vesicles were at the site of inoculatio n. Steroid treatment did not potentiate the development of secondary v esicles and did not prolong the period of virus shedding from VSV-NJ-i nfected swine. Contact transmission, as determined by shedding of viru s from the tonsil of the soft palate and the development of VSV-NJ neu tralizing antibodies, occurred in pigs in contact with animals inocula ted in the apex of the snout but not in contact animals exposed to pig s inoculated intradermally in the coronary band or intranasally. These trials show that contact transmission can occur and VSV-NJ can be she d without the development of clinical disease (i.e., vesicle formation ). Viremia was never detected in any of the experimental pigs, suggest ing that swine may not be a good amplifying host for VSV-NJ.