The Results After One Year of an Experimental Protocol Aimed at Reducing Paratuberculosis in an Intensive Dairy Herd

Abstract

Paratuberculosis or Johne's disease is caused by Mycobacterium avium subsp. paratuberculosis (MAP). The disease is characterized by a chronic and incurable enteritis in ruminants and it is responsible for significant economic losses, also raising concerns about food safety and animal welfare. Effective control is hindered by diagnostic limitations, long incubation periods, and the environmental resistance of the pathogen. This study aimed to reduce the apparent prevalence of paratuberculosis in a single intensive dairy herd through an integrated approach that combines diagnostics and management strategies. All cows over 24 months of age were tested using both fecal PCR and ELISA serology. Digital PCR (dPCR) was used to quantify MAP shedding in fecal-positive animals, enabling prioritization for removal based on environmental contamination risk. Integrating diagnostic tools allowed the precise identification and quantification of high-risk animals. Meanwhile, structural improvements and biosecurity measures were implemented on the farm. Preliminary outcomes suggest a marked reduction in herd-level MAP prevalence, lowering the seroprevalence from 7.6% to 4.5% and the fecal PCR prevalence from 6.5% to 2.8%. This case highlights the effectiveness of combining laboratory testing (serology and molecular diagnostics) and targeted changes in farm management to control paratuberculosis in high-density dairy systems.

Keywords: MAP; cattle; digital PCR; paratuberculosis; quantification.

Figure 1

Representation of the farm layout. Point number (1) indicates the sheds dedicated to the different groups of milking cows, and number (2) shows the facilities dedicated to calves and heifers. Number (3) indicates the area dedicated to pre-parturient heifers and cows in the drying phase. The areas dedicated to the calving room and infirmary are in the same structure, but properly separated (numbers (4) and (5)). Number (6) identifies the milking area. The asterisks (*) highlight the area where the mechanical scrapers deposit the slurry, which is then transferred to the storage area (7). The feed area includes stalls for silage (8), sheds for storing straw and fodder (9), and silos for feed (10). It is important to note that both the calf’s area and the area intended for heifers were only a few dozen meters away from the site intended for adult lactating cows.

Figure 2

Paratuberculosis cattle results (qPCR and serology) during the study. INC: inconclusive; POS: positive; NEG: negative; NT: not tested.

Figure 3

The decline in the apparent seroprevalence during the three visits. * indicates p < 0.05 vs. first visit.

Figure 4

Heatmap and dendrogram showing pairwise SNP distance matrix among MAP isolates in this study.

Figure 5

Maximum likelihood phylogenetic tree of the MAP isolates.