Experimental colonization of piglets and gilts with systemic strains of Haemophilus parasuis and Streptococcus suis to prevent disease

Haemophilus parasuis and Streptococcus suis art both major causes of losses during the nursery period, especially in herds using the segregated early weaning system. In this system, only a few piglets may be colonized with th e herd's prevalent systemic strain, which results in infection of naive pen mates late in the nursery. In view of these factors, the objectives of this study were: (1) to evaluate the early colonization of piglets with the far m's prevalent systemic strain of H. parasuis and S, suis as an alternative method for disease prevention; and (2) to evaluate 2 different protocols fo r experimental colonization: direct colonization of piglets and colonizatio n of piglets through nose-to-nose contact with inoculated sows. Haemophilus parasuis and S. suis isolates recovered from diseased nursery pigs were ch aracterized by the rep-PCR technique and the herd's prevalent strains were used for colonization. Piglets in the experimentally colonized groups were inoculated at 5 days of age by the oral route using a spray pump. Sows were colonized at 2 weeks prior to farrowing using a similar protocol. Although both colonization protocols were successful in getting the piglets coloniz ed, direct inoculation of 5-day-old piglets with the herd's systemic strain s of H. parasuis and S, suis tended to be more effective in reducing the mo rbidity and the mortality than the colonization of piglets by nose-to-nose contact with inoculated sows.