Objective

Mycobacterium avium subsp. paratuberculsosis (MAP) is the cause of Johne's disease that affects mainly ruminants. However the growing concern about the spread of MAP is largely due to its implication in Crohn's disease of man. In the present study, we compare three methods, PCR, serology and culture, in detection of MAP from sheep and goats.

Material and Methods

For this purpose, we compared the ability of detection of MAP in seemingly healthy sheep and goats from South-West Greece area. From a total of 30 flocks, 632 sheep and goats had fecal, serum, and whole-blood samples examined, respectively, by culture, the Complement Fixation Test (CFT), and the Polymerase Chain Reaction (PCR) targeted to IS900, respectively.

Results

The PCR produced positive results in 5.4% of the cases and the CFT produced positive 4.4% and 14.4% dubious results. Fecal cultures were negative in all but a single case. From the 408 samples that were examined both by PCR and CFT, the concord between the two tests for the CFT-positive results was 7.1%. The percentage of agreement between PCR and CFT-negative results was 95%.CFT and PCR produced similar results, since positive reactors were estimated as 4.4% and 5.4%, respectively. Although the expected failure of PCR to detect all the positive reactors with a single blood sample is probable due to the absence, or the decreased concentration, of MAP-circulating antigen in the blood, after production of adequate amounts of specific antibody. However, false positive CFT-results could also be a source of the latter or attributed to the antigenic incompatibility of the MAP strains that were detected by PCR and the antigen used in our CFT assay, which was designed with reference to cattle strains of RFLP type B-C1. Our failure to record more culture-positive results could be attributed to MAP-strains of low viability, which is consistent with the inability of our single isolate to be subcultured.

Conclusions

Given the aforementioned problems with the methods tested here, we cannot recommend to use of a single method for safe detection of MAP in sheep and goats.

Sponsorship

Attendance to this Congress was sponsored by the EU-funded project SSPE-CT-2004-501903