Infection Dynamics of Yersinia in a Pig Population

Yersinia enterocolitica infection in pigs has several implications as an enteropathogen of pigs and humans, and as a cause of false-positive serological reactions (FPSR) in tests for brucellosis (international trade implications). Swine are the primary reservoir of pathogenic Yersinia enterocolitica, although environmental survival may also be important. Few studies focused on the dynamics of infection at farm level. In pigs, Y. enterocolitica infection spreads by the feco-oral route and it is widely distributed across EU pig farms.The goal of this study was to evaluate infection dynamics in commercial pig production to support optimization of control methods.

A continuous flow 6000 pig growing farm in Germany was studied. Routine historical surveillance in had showed a variable prevalence of antibodies against Y. enterocolitica. Serum samples for a longitudinal study of 10 pigs within the herd were taken from 10 weeks up to 26 weeks of age. Antibodies against pathogenic Yersinias were tested at the Innovative Veterinary Lab of Hannover using an Elisa test (PIGTYPE YopScreen (LDL, Leipzig)).

Yersinia shedding:

1. Sock samples of pooled faeces: 10 socks were taken from the environment across the farm, sock was used to collect a pooled floor sample from each of the 10 mixed-age buildings.

2. Individual fecal samples: A cross-sectional study taking individual fecal samples was performed in 4 groups of 20 pigs ranging from 16 weeks up to 21 weeks of age to evaluate bacterial shedding.

Isolation from socks and fecal samples was attempted using the cold enrichment method at the University of Veterinary Medicine of Hannover lab.

No antibodies against Yersinia were detected at nursery and before 18 weeks of age. Seroconversion started at 18 weeks of age (10% prevalence), increasing up to 25 weeks (100% of prevalence). All the sock samples were negative at culture and the results from fecal samples are ongoing (results will be presented at the conference).

Control of Yersinia infection in pigs is not easy as several factors can contribute to transmission at herd level. In this study, piglets received from the breeding farm were negative at arrival, no infection was observed at nursery, and the spread of the infection was delayed until 16 weeks of age. Environmental faeces samples were not useful to detect the shedding of the bacteria as reported in previous studies and bacterial isolation was difficult because of low levels of excretion. Defining the farm specific infection dynamics is key to establishing effective pig-flow and environmental disinfection-based control measures for this significant bacterium.

Disclosure of Interest: None Declared.