Management factors associated with seropositivity to Lawsoniaintracellularis in US swine herds
Mark Bronsvoort, BVSc, MPVM; Bo Norby, DVM, MPVM; David P.Bane, DVM, PhD; Ian A. Gardner, BVSc, PhD
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Objective: To determine risk factors for Lawsoniaintracellularis seropositivity in the breeding and grower-finisherunits of US farrow-to-finish swine herds.
Methods: Serum was collected from 15 breeding femalesand 15 grower-finisher pigs per herd in 184 farrow-to-finish herds,a subset of 405 herds in the National Animal Health MonitoringSystem (NAHMS) Swine '95 Study that examined management, health,and productivity in herds with at least 300 finisher pigs. Serawere tested by indirect fluorescent antibody test for L intracellularis.Test results were linked with NAHMS questionnaire data, and alogistic regression model of management factors associated withL intracellularis serological status was developed. Separatemodels were used for breeding and grower-finisher units.
Results: Risk factors for seropositive breeding unitswere L intracellularis-seropositive status of the grower-finisherunit, use of a continuous system of management for the farrowingunit, and a young parity structure (<75% multiparous sows).Risk factors for seropositive grower-finisher units were Lintracellularis-seropositive status of the breeding unit,the number of pigs entering the grower-finisher stage, raisingpigs on concrete slats, and intensive management compared withraising pigs on outdoor lots.
Implications: Use of all in-all out management in thefarrowing house and an older parity structure in the sow herdwere associated with a lower risk of L intracellularisseropositivity in the breeding unit, and slatted concrete flooringin grower-finisher houses was associated with a greater risk.Alteration of these management factors might improve control ofL intracellularis infection in farrow-to-finish herds.