Comparison of sampling methods for Laivsonia intracellularis testing using qPCR

摘要

Porcine proliferative enteropathy (PPE), commonly referred to in the industry as ileitis, is an infectious intestinal disease that manifests in several forms. The etiologic agent is Lawsonia intracellularis, an obligate intracellular, gram negative bacteria that resides in intestinal cells.1 Porcine intestinal adenomatosis (PIA) refers to the chronic form of the disease, causing retarded growth and soft to watery stool in pigs 6 to 20 weeks of age, proliferative hemorrhagic enteropathy (PHE) refers to the acute form of the disease in which bloody diarrhea and sudden death of late finishing pigs and replacement gilts occurs, and a subclinical form of the disease commonly occurs in pigs that show no appatent signs of disease other than exhibiting poorer performance.2 As an economically important disease with treatments and prevention methods available,1,2,3,4 it is important to ascertain the timing of infection and subsequent shedding of the bacteria. Diagnosis oi Lawsonia intracellularis is not doneby culture, as the bacteria is very difficult to isolate and grow.5 There currently exist two main methods of antemortem diagnostic testing: detection of Lawsonia intracellularis in the feces, via PCR or indirect antibody staining techniques, and detection of znti-Lawsonia intracellularis antibodies using an indirect fluorescent antibody test (IFAT), an immunoperoxidase monolayer assay (IPMA), or a Lawsonia specific ELI-SA.6 In recent years, a quantitativepolymerase chain reaction (qPCR) assay was developed for detection of Lawsonia intracellularis in feces.7 The qPCR allows for earlier detection of infection than serological sampling, as fecal shedding of the bacteria occurs prior to seroconversion,5 andallows quantitation of the bacterial load.