Assessment of the prevalence of Mycobacterium avium subsp. paratuberculosis in commercially pasteurized milk

Area of Science:

• Veterinary Microbiology
• Food Safety Science
• Bacteriology

Background:

• Conflicting data exist regarding the heat resistance of Mycobacterium avium subsp. paratuberculosis (MAP), the causative agent of paratuberculosis (Johne's disease) in ruminants.
• Published survey results on MAP presence in industrially pasteurized milk are also inconsistent across different countries.

Purpose of the Study:

• To critically review existing data on MAP heat resistance.
• To develop a quantitative model for estimating MAP presence in pasteurized milk.
• To assess the probability of detecting MAP in pasteurized milk under industrial conditions.

Main Methods:

• Critical review of published literature on MAP heat resistance.
• Development of a quantitative model using Monte Carlo simulation.
• Analysis of MAP detection probability in 50-mL milk samples.

Main Results:

• A quantitative model was derived based on available heat resistance data.
• The simulation indicated a probability lower than 1% for detecting MAP in 50-mL pasteurized milk samples.
• Alternative explanations for higher reported frequencies, such as inadequate pasteurization or lab contamination, were considered.

Conclusions:

• Under standard industrial pasteurization conditions, the probability of MAP presence in pasteurized milk is very low.
• The study refutes hypotheses suggesting high paratuberculosis prevalence or raw milk fecal contamination as primary reasons for MAP detection.
• Further investigation into pasteurization efficacy and laboratory practices is warranted to explain discrepancies in reported findings.