Mycobacterium avium ssp. paratuberculosis (MAP) causes Johne's disease (JD) in ruminants and is shed into the milk of infected cows, which contributes to the controversial discussion about a possible link between MAP and Crohn's disease in humans. The aim of the study was to investigate the risk for the entry of MAP in the food chain via milk from dairy farms with subclinical JD. Therefore, the occurrence of MAP in the milk of a dairy herd with a low prevalence of JD was studied in single and bulk tank milk samples over a period of 23 mo and compared with MAP shedding into feces. Milk, fecal, and blood samples were taken from all cows older than 1.5 yr of age at the beginning and the end of the trial and analyzed for MAP or specific antibodies. In addition, 63 cows (33 MAP infected and 30 MAP noninfected) were selected for monthly sampling. Raw and pasteurized bulk tank milk samples were collected on a monthly basis. The milk samples were tested for MAP by real-time quantitative PCR (qPCR), and the fecal samples were tested for bacterial shedding by qPCR or solid culture. Based on the results of the herd investigations, the prevalence of cows shedding MAP was around 5%; no cases of clinical JD were observed during the study period. The results of the ELISA showed high variation, with 2.1 to 5.1% positive milk samples and 14.9 to 18.8% ELISA-positive blood samples. Monthly milk sampling revealed low levels of MAP shedding into the individual milk samples of both MAP-infected and noninfected cows, with only 13 cows shedding the bacterium into milk during the study period. Mycobacterium avium ssp. paratuberculosis was not detected by qPCR in any raw or pasteurized bulk tank milk sample throughout the study. A significant positive association could be found between MAP shedding into milk and feces. From the results of the present study, it can be concluded that MAP is only shed via milk in a small proportion of cows with subclinical JD for a limited period of time and is diluted below the detection level of qPCR within the bulk tank milk of these herds. These findings indicate that dairy herds subclinically infected with JD pose only a minor source for human MAP consumption with milk and milk products.

Zusammenfassung Gegenstand und Ziel Darstellung der Untersuchungsergebnisse von 150 Abortfällen beim Rind aus dem Jahr 2018 (Januar–September). Material und Methoden Je nach Einsendematerial und Anforderung erfolgten serologische, bakteriologische und/oder molekularbiologische Untersuchungen zum Nachweis von in Österreich anzeigepflichtigen und nicht anzeigepflichtigen Aborterregern. Ergebnisse Neben rein tierpathogenen Infektionserregern konnten bei je 1 Tier Brucella melitensis, Salmonella Dublin und bei 2 Feten Coxiella burnetii nachgewiesen werden. Schlussfolgerung Die Ergebnisse zeigen, dass im Zusammenhang mit Aborten immer eine besondere Sorgfaltspflicht hinsichtlich Schutz der exponierten Person (Landwirt, Tierarzt, Laborpersonal) erforderlich ist. Auch mit dem Wiederauftreten von lange nicht mehr aufgetretenen Tierseuchen ist jederzeit zu rechnen, wie aus dem aktuellen Brucella-Nachweis ersichtlich wird. Klinische Relevanz Wichtigste Voraussetzung für eine hohe Aufklärungsrate bei infektiös bedingten Aborten stellt die Wahl des geeigneten Probenmaterials dar, nämlich Fetus mit Plazenta und maternale Blutproben. Aufgrund des großen Erregerspektrums ist die Abortdiagnostik umfangreich und aufwendig.

This study aimed to investigate the prevalence of Mycobacterium avium subsp. paratuberculosis (MAP) in small ruminants in Austria by testing 22,019 serum samples with ELISA for the presence of specific antibodies. Furthermore, detailed investigations in five MAP-infected goat herds were carried out by ELISA, qPCR and bacterial culture. The found animal-level apparent MAP seroprevalence was 2.0% for goats and 0.7% for sheep (calculated true prevalence 3.5% and 1.2%, respectively). Herd-level apparent MAP seroprevalence was 11.1% for goat herds and 8.9% for sheep flocks. Significant risk factors for seropositivity in goat herds were: herd size, animal trading, farmed as a dairy herd, Animal Health Service membership and cohabitation with farmed game. For sheep flocks, seroprevalence was significantly higher in flocks with animal trading and where cattle or goats were kept in the flock, respectively. The overall apparent within-herd MAP seroprevalence in the five goat farms investigated was 21.8% (11.7%–28.0%, calculated true seroprevalence 38.6%) and an overall rate of MAP shedding of 12.3% was detected (5.0%–24.7%). It was possible to identify MAP by culture using boot swab samples in each herd. The results indicated a moderate MAP infection rate in small ruminants in Austria.