Development and field validation of an indirect ELISA for serosurveillance of Ornithodoros lahorensis exposure.

BACKGROUND

Ornithodoros lahorensis is the primary vector of numerous tick-borne diseases. Effective tick surveillance could facilitate the prevention of tick-borne diseases. Direct surveillance methods for tick bites are impractical, the development of an indirect approach to detect specific antibodies against tick salivary proteins in animal samples would provide a more convenient surveillance and diagnostic tool. Previous studies have confirmed that some salivary gland proteins can be used as detection markers for tick bites.

METHODS

The recombinant BTSP protein of O. lahorensis (rOl-BTSP) was expressed and purified. rOl-BTSP was subjected to sequence alignment analysis, and validated as a serological detection target for O. lahorensi exposure by Western blot analysis. Then, a novel ELISA method for detecting O. lahorensis bites in sheep (S-iELISA) was developed by optimizing critical parameters, including antigen coating concentration, serum dilution. The sensitivity and specificity of the S-iELISA method were evaluated. And the S-iELISA were further applied to test 455 sheep serum samples from Xinjiang and Inner Mongolia in China.

RESULTS

Sequence homology analysis revealed that Ol-BTSP exhibited only 30.5 % amino acid identity with its homologs from both hard ticks and soft ticks. And the serum from mice bitten by O. lahorensis exhibited specific immunoreactivity with rOl-BTSP, while the cross-species antibody tests showed no reactivity, confirming the diagnostic potential of Ol-BTSP for detecting O. lahorensis exposure. The developed S-iELISA exhibited excellent diagnostic accuracy, with a sensitivity of 93.3 % (95 % CI: 70.2-99.7 %) and a specificity of 96.7 % (95 % CI: 82.8-99.9 %) in validation studies. The seroprevalence rate of O. lahorensis exposure in serum samples collected from Xinjiang and Inner Mongolia were 10.45 % and 3.09 %, respectively.

CONCLUSIONS

The S-iELISA method established in this study was a reliable tool for detecting and monitoring O. lahorensis exposure in sheep. And the serological diagnostic method based on rOl-BTSP showed great promise for enhancing the surveillance and management strategies for O. lahorensis-borne diseases.