Evaluation of antemortem polymerase chain reaction and serologic methods for detection of Lawsonia intracellularis-exposed pigs.
OBJECTIVE
To evaluate polymerase chain reaction (PCR) for detection of Lawsonia intracellularis DNA in feces and an indirect fluorescent antibody test (IFAT) for detecting serum IgG antibodies in pigs exposed to L intracellularis.


METHODS
15 seven-week-old pigs and 42 three-week-old pigs.


METHODS
During 3 experiments, 23 pigs were inoculated with a pure culture of L intracellularis, 31 pigs served as noninoculated controls, and 3 pigs were used as sentinels. Fecal shedding of L intracellularis was monitored by use of PCR analysis at 7-day intervals. At euthanasia, the ileum was obtained for PCR and histologic analyses. Serum was obtained at 7-day intervals for use in the IFAT.


RESULTS
Polymerase chain reaction analysis detected L intracellularis DNA in the feces of 39% of the inoculated pigs; by postinoculation days 21 to 28, 90% of inoculated pigs developed IgG antibodies detected by IFAT. Neither L intracellularis DNA nor IgG antibodies were detected in any of the noninoculated control pigs at euthanasia. Sera from pigs inoculated with enteric pathogens other than L intracellularis did not contain detectable antibodies that reacted with L intracellularis by use of the IFAT.


CONCLUSIONS
The IFAT for L intracellularis IgG antibody detection appeared to be a more sensitive antemortem test for detecting pigs experimentally infected with L intracellularis than was a PCR method for direct detection of the organism in the feces.


CONCLUSIONS
Not all animals that are infected with L intracellularis shed the organism in feces at detectable amounts.
Knittel
J P
JP
Boehringer Ingelheim/NOBL Laboratories Inc, Ames, IA 50010, USA.
Jordan
D M
DM
Schwartz
K J
KJ
Janke
B H
BH
Roof
M B
MB
McOrist
S
S
Harris
D L
DL
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D004269:DNA, Bacterial / Q000032:analysis; D005243:Feces / Q000382:microbiology; D019084:Fluorescent Antibody Technique, Indirect; D006090:Gram-Negative Bacteria / Q000302:isolation & purification*; D016905:Gram-Negative Bacterial Infections / Q000097:blood / Q000175:diagnosis / Q000662:veterinary*; D007074:Immunoglobulin G / Q000097:blood; D016133:Polymerase Chain Reaction / Q000379:methods; D013552:Swine; D013553:Swine Diseases / Q000097:blood / Q000175:diagnosis*
D000907:Antibodies, Bacterial; D004269:DNA, Bacterial; D007074:Immunoglobulin G