Detection of Low MAP Shedder Prevalence in Large Free-Stall Dairy Herds by Repeated Testing of Environmental Samples and Pooled Milk Samples

Abstract

An easy-to-use and affordable surveillance system is crucial for paratuberculosis control. The use of environmental samples and milk pools has been proven to be effective for the detection of Mycobacterium avium subsp. paratuberculosis (MAP)-infected herds, but not for monitoring dairy herds certified as MAP non-suspect. We aimed to evaluate methods for the repeated testing of large dairy herds with a very low prevalence of MAP shedders, using different sets of environmental samples or pooled milk samples, collected monthly over a period of one year in 36 herds with known MAP shedder prevalence. Environmental samples were analyzed by bacterial culture and fecal PCR, and pools of 25 and 50 individual milk samples were analyzed by ELISA for MAP-specific antibodies. We estimated the cumulative sensitivity and specificity for up to twelve sampling events by adapting a Bayesian latent class model and taking into account the between- and within-test correlation. Our study revealed that at least seven repeated samplings of feces from the barn environment are necessary to achieve a sensitivity of 95% in herds with a within-herd shedder prevalence of at least 2%. The detection of herds with a prevalence of less than 2% is more challenging and, in addition to numerous repetitions, requires a combination of different samples.

Progress in Paratuberculosis Control Programmes for Dairy Herds

“…In a simulated herd with a within-herd prevalence of faecal shedders of 2%, the herd level sensitivity of a qPCR assay of 1:5 pooled faecal samples of 80 out of 300 adult cattle was determined to be 78% [18]. The herd-level sensitivity of testing pooled milk samples and environmental samples was considerably lower [19,20]. However, by including results of seven repeated monthly samplings of pooled faeces from the barn environment and testing these samples with culture as well as direct qPCR, a cumulative herd-level sensitivity of 95% could be reached in herds with a within-herd prevalence of shedders of ≥2% [19,20].…”

“…The herd-level sensitivity of testing pooled milk samples and environmental samples was considerably lower [19,20]. However, by including results of seven repeated monthly samplings of pooled faeces from the barn environment and testing these samples with culture as well as direct qPCR, a cumulative herd-level sensitivity of 95% could be reached in herds with a within-herd prevalence of shedders of ≥2% [19,20].…”

“…Simulation studies indicated that whole-herd examinations by individual milk ELISA may be suitable to identify herds with a high probability of freedom from Map infection, i.e., a high probability of a within-herd prevalence below a design prevalence of 5%, even though eleven annual herd examinations are required to reach a 95% confidence of freedom in test-negative herds [57][58][59][60]. Similarly, test results of repeated environmental samples and pooled milk samples might be used to estimate the probability of freedom from Map infection in herds under surveillance [19,20]. In line with these results, a review of the Dutch MQAP recommended to include 'low-risk trade of cattle' within the objectives of the programme and to identify a subset of herds with a high probability of freedom from infection as a source of low-risk cattle for trade [48].…”

Verbreitung der Paratuberkulose in Thüringer Schaf- und Ziegenherden

“…Eine einmalige Beprobung mittels Umgebungskotproben genügt nicht, um solche Herden mit ausreichender Sicherheit zu erkennen. Wahrscheinlich wären wiederholte Beprobungen mittels Umgebungskotproben notwendig, um die Sensitivität des diagnostischen Verfahrens zu erhöhen, so wie das für Rinder gezeigt wurde [19].…”

Mycobacterium avium subsp. Paratuberculosis in Different Environmental Samples from a Dairy Goat Barn—Implications for Sampling Strategies for Paratuberculosis Diagnostic and Prevention

“…However, herds with a low prevalence may be misclassified as uninfected due to negative environmental samples caused by intermittent pathogen shedding or dilution as well as dissemination effects [17]. For this reason, repeated collection of multiple environmental samples is recommended to increase sensitivity [9,19,20].…”