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.

Evaluation of Mycoplasma hyopneumoniae inactivated vaccine in pigs under field conditions.

An inactivated vaccine prepared from broth culture supernatant of Mycoplasma hyopneumoniae with an aluminum adjuvant was evaluated in three herds (herd A: specific pathogen-free herd, herd B: high health status herd with no clinical signs of respiratory infection, herd C: low health status herd with serious epidemiological and economical problems). A total of 212 pigs from the three herds were divided into two groups. One group was injected twice with the vaccine at 4-week intervals and the other was a control group. No adverse reactions were noted following the vaccinations either systematically or locally in any of the vaccinated pigs from any of the herds. In herd A, the vaccination provided antibody response within 4 weeks after the second vaccination and antibody responses continued for more than 12 weeks. In herds B and C, the number of pigs with lung lesions, mean percentage of lung lesions, and the numbers of M. hyopneumoniae recovered from pigs at slaughter in the vaccinated group were significantly (P < 0.05) reduced compared to the control group. Furthermore, vaccination resulted in improved average daily weight gain (ADG), improved feed conversion ratio (FCR), and improved days to market weight in herd C, whereas no difference in growth performance was shown in herd B. It is suggested that the inactivated vaccine prepared from broth culture supernatant of M. hyopneumoniae is effective in reducing clinical signs and lung lesions. Also, vaccination resulted in improved growth performance in herds where clinical signs and economic losses were significant.

Protection from caseous lymphadenitis in sheep by spraying iodine tincture on shearing wounds.

The effect of spraying shearing wounds with iodine tincture on Corynebacterium pseudotuberculosis infection in lambs was examined. The ELISA-negative lambs which had received some visible wounds during their first shearing were randomly divided into two groups: one was sprayed with iodine tincture on wounds after shearing, and the other was not. Anti-C. pseudotuberculosis toxin titers were measured by ELISA. The seroconversion ratio of the group with iodine tincture treatment 3 months after shearing was smaller than that of the untreated group (P < 0.05). These results suggest that treatment of shearing wounds with iodine tincture is effective in the protection of C. pseudotuberculosis infection in lambs.

Seroepidemiological evidence that shearing wounds are mainly responsible for Corynebacterium pseudotuberculosis infection in sheep.

Anti-Corynebacterium pseudotuberculosis toxin titers were examined by an enzyme-linked immunosorbent assay (ELISA) at 3 to 5 month intervals in sheep of three age groups (lambs, 1- and 2-year-old sheep). A significant increase in the ELISA-positive ratio was found only in July, 3 months after shearing, in 1- and 2-year-old sheep. A decrease in the positive ratio was found in the same month in lambs, possibly due to a decrease in maternal antibodies. Since the 1- and 2-year-old sheep had been sheared in April, it was considered that the increase in the positive ratio in July might be closely related to the shearing in April.