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Comparison of three Mycoplasma bovis antibody ELISAs on serum from 3-5-week-old dairy calves using Bayesian latent
Jolien Vandewalle1, Justine Clinquart2, Wouter van Mol3
1Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, UGent Calf Health, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium. Jolien.Vandewalle@UGent.be.
Background:
Controlling Mycoplasma bovis is challenging in veal and dairy beef systems that source young calves from multiple origins. Pre‑purchase testing may help reduce pathogen introduction, with serology being the most accessible option. Additionally, given current EFSA recommendations to increase the minimum transport age to five weeks, this period represents the relevant time frame for pre‑purchase examination. However, antibody test performance in 3-5‑week‑old calves during acute infection is unknown. This study aimed to (1) compare the diagnostic accuracy of three commercial antibody ELISAs (ID‑screen, Bio K302 and Bio K432) in Belgian male dairy calves aged 3-5 weeks using Bayesian latent class models at manufacturer and optimized cutoffs, and (2) assess the effect of seroprevalence on predictive values.
Results:
A prospective diagnostic test accuracy study was conducted using 194 serum samples from calves aged 20-38 days. First, samples were analyzed with each ELISA according to manufacturer's instructions. Next, test performance, as well as predictive values were evaluated using both manufacturer and optimized cutoff values. Using manufacturer's cutoffs, sensitivities for ID‑Screen, Bio K302, and Bio K432 were 69.1%, 24.6%, and 68.7%, respectively, and specificities were 97.8%, 95.6%, and 97.9%. Optimized cutoffs improved sensitivities to 82.2%, 46.2%, and 88.9%, with specificities of 97.5%, 90.7%, and 89.3%. At a seroprevalence of 7.5%, positive predictive values (PPV) were 72.6% for Bio K432, 71.8% for ID‑Screen, and 31.2% for Bio K302, while negative predictive values (NPV) were similar for Bio K432 and ID‑Screen (both 97.5%) and slightly lower for Bio K302 (94%). At 20.8% seroprevalence, PPV increased for ID‑Screen (89.6%) compared with Bio K432 (68.6%) and Bio K302 (56.6%), while NPV remained high for ID‑Screen and Bio K432 (95.4% and 96.8%) but declined for Bio K302 (86.5%).
Conclusions:
During acute infection in 3-5‑week‑old calves, serological antibody testing against M. bovis shows strong potential as a rule‑in diagnostic tool. ID‑Screen and Bio K432 performed best, making them suitable for implementing feedback mechanisms to herds of origin, but they do not provide the strong rule-out capacity needed for effective screening.
