Detection of Lawsonia intracellularis by oral fluids and fecal samples in Canadian swine

Abstract

Objectives: The study objectives were to 1) describe the proportion of Lawsonia intracellularis-positive samples in unvaccinated and vaccinated Canadian swine herds during the mid- and late-finishing phases; 2) compare the probability of detecting L intracellularis by quantitative polymerase chain reaction using fecal samples (FS) and oral fluids (OF); and 3) investigate risk factors of L intracellularis detection using FS and OF. Material and methods: Site demographics and vaccination protocols were obtained from 40 Canadian swine sites via questionnaire. Three OF and 3 FS were collected per site once during the mid-finisher (15-17 wk of age) and once during the late-finisher (20-22 wk of age) production stages. Results: Half of all investigated production sites were positive for L intracellularis. A 2-fold increase in L intracellularis detection rate was observed for OF compared to FS (odds ratio = 2.36; 95% CI, 1.24-4.49; P = .009). The presence of porcine circovirus type 2 (PCV2) had a 5-fold increased risk of L intracellularis positivity compared to sites without PCV2 (incidence rate ratio [IRR] = 4.99; 95% CI, 1.29-20.23; P = .02). A higher positive rate was found for sites with L intracellularis outbreaks within the last 2 years (IRR = 3.08; 95% CI, 1.51-6.37; P = .002). Implications: This study presents evidence that OF may have a higher detection rate compared to FS for L intracellularis. Herds with PCV2 or exposure to recent L intracellularis outbreaks may be at increased risk of harboring L intracellularis and warrant additional investigation.