Rapid application of long-acting ceftiofur can prevent death losses associated with Streptococcus equi subspecies zooepidemicus in pigs

Abstract

Objective: Introduction of Streptococcus equi subspecies zooepidemicus strains into naive populations results in field mortality rates of 30% to 50% over 5 to 10 days. Because of the rapid disease progression, our goal was to determine whether antibiotic intervention could control S zooepidemicus disease in a group of animals following development of clinical signs. Materials and methods: Thirty-two pigs were challenged with S equi subsp zooepidemicus. Following the development of clinical signs, 16 were treated with long-acting, injectable ceftiofur. Seven unchallenged pigs served as controls. Clinical signs were monitored following challenge and survival was compared between groups. Antibody titers were measured on day 0 and day 30 post challenge. On day 30 post challenge, 3 contact pigs were commingled with 2 treated animals to evaluate S equi subsp zooepidemicus transmission. Results: Ceftiofur treatment eliminated clinical signs in 15 of 16 animals. However, multiple treatments were required to control disease in treated animals (2-3 doses providing 12-18 days of coverage). Antibody titers to S equi subsp zooepidemicus increased in challenged animals treated with ceftiofur, indicating sufficient exposure for immune stimulation. No contact pigs developed clinical signs of S equi subsp zooepidemicus following exposure. Implication: Rapid application of injectable antibiotics is a viable method to reduce losses due to the introduction of S equi subsp zooepidemicus into a naive group of pigs and may help prevent transmission to contact animals following recovery.