Lawsonia intracellularis

Test codes:
B0035 - Ultrasensitive qualitative detection of Lawsonia intracellularis by real time polymerase chain reaction
P0015 - Equine GI/diarrhea panel (includes Lawsonia and other pathogens)

Proliferative enteropathy, also known as proliferative ileitis, is caused by infection with Lawsonia intracellularis, an obligate intracellular, curve-shaped, argyrophilic bacterium. The disease has been detected in domestic and laboratory animals including primates, pig, horse, dog, rat, ferret, guinea pig, rabbit and hamster. The disease has been reported sporadically in foals 3-7 months of age and one outbreak involving 3 different breeding farms has been described. All reported cases were in the eastern half of Canada or the United States. The swine industry suffers the most significant impact from this disease. The disease has two clinical manifestations in pigs: an acute hemorrhagic form often called porcine hemorrhagic enteropathy, and a more chronic proliferative form often referred as porcine intestinal adenomatosis.

Environmental contamination with feces of infected animals appears to be the most important route of transmission of disease, but it is currently unknown how long Lawsonia intracellularis can remain infectious outside the animal. Infection occurs most often during the post-weaning period, when passive maternal immunity declines. After ingestion, the bacteria infect intestinal proliferating crypt epithelial cells and multiply within the apical cytoplasm. There is no evidence of infection of tissues other than intestine. Most infected animals have subclinical infection but shed the bacteria in their feces, leading to environmental contamination. Clinical manifestation of an infection can be triggered by stressors, such as overcrowding, transport, change in diet, and experimental manipulation.

Bacterial culture and isolation of the bacteria are difficult because cultured enterocytes are required to support the growth of Lawsonia intracellularis. Electron microscopy can be used to detect the curved bacterial rods in apical cytoplasm of enterocytes but this is a very time-consuming process and few laboratories have such capability. Immunohistochemical detection can be performed on formalin-fixed, paraffin-embedded tissue from affected intestine to detect the bacteria in following biopsy or necropsy, but this is also a very time-consuming process. Molecular detection using PCR is the most sensitive, rapid and specific method to confirm presence of the Lawsonia intracellularis genome within tissue samples (Jones et al., 1993).

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of Lawsonia infection.
• Ensure that horse populations are free of Lawsonia
• Early prevention of spread of this bacterium
• Minimize personnel exposure to this bacterium
• Safety monitoring of biological products that derive from horses

References:
Jones, G. F., Ward, G.E., Murtaugh, M.P., Lin, G. and Gebhart, C.J. (1993) Enhanced detection of intracellular organism of swine proliferative enteritis, ileal symbiont intracellularis in feces by polymerase chain reaction. J. Clin. Microbiol. 31:2611-2615.

Specimen requirements: 1 ml feces, or fresh or fixed ileum tissue, shipped overnight at room temperature; or frozen ileum tissue.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected