Protection of Buffaloes Against Oedematous Skin Disease by Recombinent-bacterin and Toxoid-bacterin Vaccines

3 Abstract: The protective efficacy of two formulated vaccines against Corynebacterium pseudotuberculosis biotype 2 was tested on male buffalo-calves (aged 6-8 months) from a herd free from Oedematous Skin Disease (OSD). Using a virulent strain of C. pseudotuberculosis biotype 2 (nitrate positive), locally isolated from buffalo severely infected with OSD, an experimental model of OSD was developed in which the manifestation of disease were equivalent to the naturally observed infection in Egypt. Subsequently the capacity of the two experimental vaccines to protect against experimental challenge was determined. The animals were divided into 3 groups each of 3 animals. Group 1 was immunized with a recombinant derivative of phospholipase D (r PLD) combined with formalin killed bacterin, while group 2 was immunized with crud supernatant of C. pseudotuberculosis toxoid and bacterin. Group 3 consisted of unvaccinated animals. All groups were challenged intradermally in hairless areas with live bacteria 6 weeks after last vaccination. Unvaccinated animals showed manifestations of OSD observed in naturally diseased animals. Following homologues experimental challenge, both vaccines were observed to confer protection against infection in all animals. In each of the 2 vaccinated groups there was a titer rise of anti-PLD antibodies following first dose of vaccination measured with ELISA test and titer decreased gradually irrespective of bosstering or challenge exposure. In second vaccinated group the titer of antibodies decreased gradually to reach the level of control unvaccinated animals through 3 months of challenge, while the titer in r PLD-bacterin vaccinated group titer persisted to 50 during the same period. The present investigation indicates that the development of OSD following intradermal inoculation with C. pseudotuberculosis can be reduced by an inactivated vaccine containing inactivated PLD in the form of recombinant PLD or formalin-inactivated crude supernatants in combination with whole formalin-killed bacterin. Vaccination is recommended to be performed at the end of February to cover the summer months before the appearance of hippobosca equina the main transmitter of the causative agent to buffaloes.