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

Abstract

Environmental samples are often used to classify the paratuberculosis status of cattle herds. The disease is caused by Mycobacterium avium subsp. paratuberculosis (MAP), predominantly through oral ingestion during infancy. In this explorative study, the presence of MAP was determined in the barn environment of a paratuberculosis-infected vaccinated dairy goat herd. A total of 256 bedding, dust, feed, and water samples were collected at eight time points and examined using culture and qPCR. Detection rates of both methods were compared, and factors determining MAP confirmation were identified. MAP was cultured from 28 bedding and one dust sample, while MAP DNA was detected in all materials (117/256). Samples from high animal traffic areas and those collected during the indoor season were more likely to yield positive culture and qPCR results. Cultivation of MAP from kidding pens indicated this area as a possible infection site. Dust proved to be the most suitable material for detecting MAP DNA, as bedding was for MAP culture. Environmental sampling was demonstrated to be an effective way to detect MAP in a dairy goat herd. qPCR results could confirm herd infection, while culture results provided insight into crucial areas for MAP transmission. These findings should be considered when designing farm-specific paratuberculosis control plans.

Keywords: Johne’s disease; MAP; bedding; control program; dust; environmental sampling; feed; small ruminants; transmission; water.

Figure 2

Heatmap indicating the percentage of culture-positive bedding samples for Mycobacterium avium subsp. paratuberculosis from the different sampling sites in the dairy goat barn over the study period. Dry goat/kidding pens (D) were set up temporarily within quadrants Q1 and Q2 during the kidding season in 2020 and 2021.

Figure 3

Heatmap indicating the percentage of qPCR-positive bedding (A) and dust (B) samples for Mycobacterium avium subsp. paratuberculosis from the different sampling sites in the dairy goat barn over the study period. Dry goat/kidding pens (D) were set up temporarily within quadrants Q1 and Q2 during the kidding season in 2020 and 2021. No dust samples were collected from the barn exits (E), the milking parlor (G), and its exit (H).

Figure 1

Sampling schedule for fecal and environmental samples between 2018 and 2022. HS = herd sampling (♦), ES = environmental sampling (✕). Grazing seasons are marked as green boxes.

Figure 4

Distribution of the C_t values of qPCR analysis relative to the calculated growth index (semi-quantitative culture results) of Mycobacterium avium subsp. paratuberculosis in the different sampling materials (A): bedding, (B): dust, (C): feed, (D): water displayed with the qPCR classification cut-off (40.0; dashed line).