A cross-protection experiment in pigs vaccinated with Haemophilus parasuis serovars 2 and 5 bacterins, and evaluation of a bivalent vaccine under laboratory and field conditions.

Cross-protection between Haemophilus parasuis serovars 2 and 5 was examined in pigs using a bacterin based vaccine, and subsequently the safety and efficacy of a bivalent vaccine were evaluated. Upon intratracheal challenge of a serovar 2 or 5 strain, pigs immunized with a monovalent vaccine were protected against challenge with a homologous serovar strain, but not with a heterologous serovar strain. Immunization with a bivalent vaccine containing both serovars 2 and 5 bacterins conferred protection in pigs against lethal challenge with each of the serovar strains. A total of 86 pigs from two SPF herds were injected with the bivalent vaccine intramuscularly twice at a four-week interval. No adverse reactions following the vaccination were observed. On day 7 after the second vaccination, vaccinated and non-vaccinated control pigs from herd A were transferred to herd B, where Glasser's disease had broken out. Pigs in the control group developed clinical signs of the disease, and 6 of 8 (75%) pigs died until slaughter, in contrast with only 4 of 46 (9%) pigs in the vaccinated group. In herd C, where there was no outbreak of Glasser's disease, complement fixation antibody titer was raised only in the vaccinated group. A challenge experiment on days 20 and 79 after the second vaccination showed that only the vaccinated pigs were protected. From these findings, the safety and efficacy of the bivalent vaccine were confirmed under laboratory and field conditions.

Immunoperoxidase procedures for rapid detection of bovine viral diarrhea-mucosal disease virus antigen.

Bovine viral diarrhea-mucosal disease (BVD-MD) virus antigen was detected in bovine fetal muscular cells from sera of 42 cattle persistently infected with noncytopathic BVD-MD virus by the indirect immunoperoxidase procedure (IIP) but not from sera of 100 apparently healthy cattle. These findings agreed with the results obtained by the interference method. Furthermore, BVD-MD virus antigens were detectable in the smears of buffy coats by the IIP procedure and in the formalin-fixed tissue sections by the avidin-biotin-peroxidase complex procedure. These procedures are therefore expected to be useful for rapid detection of BVD-MD virus antigen.