Poster Presentation The 3rd Prato Conference on the Pathogenesis of Bacterial Diseases of Animals 2014

IFAT and ELISA phase I/phase II as tools for the identification of Q fever chronic shedders in cattle (#31)

Laura Lucchese 1 , Katia Capello 2 , Antonio Barberio 3 , Federica Zuliani 1 , Silvia Marchione 1 , Alda Natale 1
  1. Serology Laboratory, Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro (PD), Italy
  2. Health Structure’s staff, Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro (PD), Italy
  3. Istituto Zooprofilattico Sperimentale delle Venezie, Vicenza, Italy

The chronic shedders identification is a critical issue for the control of Q fever in cattle, but at present none of the available immunological assays can discriminate the infection status. Following the example of the human protocols for the assessment of Q fever infection status, we evaluated two modified commercial kits for anti-C.burnetii phase I and II antibodies detection: ELISA and IgG/IgM IFAT.
Sera were collected in 4 dairy herds with confirmed Q fever. A total of 99 animals were sampled 3 times over 6 months and classified in 5 groups with routine serological tests and PCR: NI- (non infected, seronegative, not shedder, n=26); NI+ (non infected, seropositive, not shedder, n=29); CS (seropositive chronic shedder, n=12); OS+ (occasional seropositive shedder, n=20); OS- (occasional seronegative shedder, n=12).
All the 297 samples were tested with the modified ELISA kit and a selection of 107 samples was made for IFAT. The groups NI- and OS- were confirmed as negative, consequently only the groups NI+, CS e OS+ were considered for the evaluation.
Differences were observed among groups in ELISA, permitting to discriminate CS (more relevant from an epidemiological point of view) from NI+ and OS+. Overall, NI+ showed significantly lower S/P values with respect to CS and OS+. Considering the interaction between group and phase, in OS+ the S/P values of phase I resulted significantly higher than S/P values of phase II.
All the ELISA positive samples were confirmed in IgG IFAT and only 5 samples were IgM positive. The IgG IFAT highlighted that NI+ had significantly lower titers than CS; OS showed no significant differences, with halfway values between NI+ and CS. All groups had phase I > phase II titers.
The ELISA seems to perform better as tool for the chronic status identification, showing significant differences among groups.