Specificity of serological test for detection of tuberculosis in cattle, goats, sheep and pigs under different epidemiological situations

Abstract

Background Serum antibody detection has potential as a complementary diagnostic tool in animal tuberculosis (TB) control, particularly in multi-host systems. The objective of the present study was to assess the specificity (Sp) of an enzyme-linked immunosorbent assay (ELISA) based on the new multiprotein complex P22 for the detection of specific antibodies against the Mycobacterium tuberculosis complex (MTC) in the four most relevant domestic animals acting as MTC hosts: cattle, goat, sheep and pig. We used sera from an officially TB-free (OTF) country, Norway, and from a non-OTF one, Spain. The samples included sera from goats that had been vaccinated against M. avium subsp. paratuberculosis (MAP) and sheep from a herd in which Corynebacterium pseudotuberculosis had been isolated. Results In cattle, the Sp ranged from 92.5 (IC95% 90.7–94) to 99.4% (IC95% 98.3–99.8) depending on the cut-off used and the origin of the samples (Spain or Norway). Sp in cattle (cut-off point 100) was significantly higher ( P < 0.05) for Norwegian samples. By contrast, Sp in goats was consistently low at the 100 cut-off [30.9 (CI95%23.4–39.5)-78% (CI95% 68.9–85)]. A higher cut-off of 150 improved Sp in Norwegian goats [97% (CI95% 91.6–99)], but still yielded a poor Sp of 56.1% (CI95% 47.3–64.6) in Spanish goats. In Norway at the 100 cut-off the Sp was 58.3 (CI95% 42.2–72.9) and 90.6% (CI95% 81–95.6) in MAP vaccinated and non-vaccinated goats, respectively, indicating interference due to MAP vaccination. Sp in sheep was between 94.4 (CI95% 91.7–96.3) and 100% (CI95% 96.3–100) depending on the cut-off and country, and no diagnostic interference due to infection with C. pseudotuberculosis was recorded. Sp in pigs was 100%, regardless the cut-off point applied, and no significant differences were observed between pigs from Norway and from Spain. Conclusions Due to its excellent Sp in pigs and acceptable Sp in cattle and sheep, this ELISA may constitute a suitable option for TB screening at herd level, particularly in OTF-countries.

Evaluation of P22 Antigenic Complex for the Immuno-Diagnosis of Tuberculosis in BCG Vaccinated and Unvaccinated Goats

“…Even so, the Sp was within ranges (95-100%) described for STAND-IGRA in previous studies (11,38,45). This mild reduction in Sp could be explained by the high concentration of P22 used for stimulation of whole blood (20 µg/ml) and by the fact that P22 complex contains 21 proteins also present in M. avium (23), which can cause cross-reactivity with MAP vaccination and/or infection. Indeed, the interference of MAP vaccination on STAND-IGRA has been previously observed in adult MAP-vaccinated goats (13,14,45).…”

“…Interestingly, the Se was significantly enhanced when using P22 and MPB83 ELISAs in parallel. Thus, even though MPB83 is a major component of the P22 complex, specific IgGs of some infected animals were only detectable using the MPB83 purified recombinant protein alone, while others were only detected using the P22 complex, which contains additional serodominant epitopes (23).…”

“…Two TB control scenarios were hypothesized in order to study the performance of each diagnostic test: the conventional (TB unvaccinated) scenario, using data from herds A and B, and the BCG-vaccinated (TB-VAC) scenario, using data from herds A and C. Se was calculated using data from herd A, and Sp was calculated using data from herds B and C depending on TB control scenario ( Table 2) and used at concentrations recommended by the Spanish Ministry (9). The protein complex P22 was produced by immunopurification of PPD-B (CZ Vaccines) as described previously (23) and prepared at a concentration of 500 µg/ml (unpublished data). The DIVA reagent based on a cocktail of recombinant ESAT-6 and CFP-10 proteins (500 µg/ml) (31) and the recombinant MPB83 (MPT83) protein (500 µg/ml) (32) were purchased from Lionex (Braunschweig, Germany).…”

Comparison of recombinant MPB70 and SahH and a native 20-kDa protein for the detection of bovine tuberculosis by ELISA

“…bTB ELISA using purified and recombinant antigens will be useful for individual tests as well as herd screening [1,2,26]. In slaughterhouses, randomly selected serum samples can be evaluated, followed by the tracking of antibody-positive reactors [12,22,30].…”

“…Positive control and negative control sera were used for each ELISA for validation. ELISA results were analysed according to three criteria, the OD value, S/N ratio, and S/P ratio [1,17,22,23]. The optimal method for effectively diagnosing bovine tuberculosis was determined by comparisons of the sensitivity and specificity of each parameter.…”