Efficacy of dairy on-farm high-temperature, short-time pasteurization of milk on the viability of Mycobacterium avium ssp. paratuberculosis

Abstract

Feeding pasteurized milk to suckling calves is a popular practice used increasingly on dairy farms. Waste milk is frequently fed to calves because of its high nutritional value and economic benefits compared to milk replacement products. However, one of the disadvantages of feeding waste milk is the potential for exposure to a high number of bacterial contaminants, which may lead to serious illnesses or infections in calves. One of these contaminants is Mycobacterium avium ssp. paratuberculosis (MAP), the causative agent of Johne's disease (paratuberculosis). The transmission and distribution of paratuberculosis in dairy herds occurs mostly through the feeding newborn calves with contaminated colostrum or milk, because this age group is believed to be most susceptible to infection. To reduce the risk of transmission of pathogens, on-farm pasteurization of milk has become increasingly popular. In this study, we analyzed the efficacy of a new commercial high-temperature, short-time pasteurizer (73.5°C for 20 to 25 s) in terms of MAP inactivation under experimental on-farm conditions. The pasteurizer uses a newly developed steam-heating technique, allowing for the pasteurization of the transition milk without clumping. In 3 independent trials, we spiked fresh raw milk samples to a level of 10 7 or 10 4 viable MAP cells/ mL before pasteurization. We examined the thermal inactivation and viability of MAP using culture and a D29 bacteriophage-based assay. To verify the identity and number of MAP cells, we also performed PCR assays. Pasteurization of the inoculated milk (10 7 and 10 4 MAP cells/mL) resulted in a remarkable reduction in viable MAP cells. The mean inactivation rate of MAP ranged from 0.82 to 2.65 log 10 plaque-forming units/ mL, depending on the initial MAP amount inoculated and the addition of conservative agents to the pasteurized milk. Nevertheless, approximately 10 3 MAP cells/ mL remained viable and could be transferred to calves after high-temperature, short-time pasteurization of milk.

Systematic Assessment of Mycobacterium avium Subspecies Paratuberculosis Infections from 1911–2019: A Growth Analysis of Association with Human Autoimmune Diseases

“…MAP research coupled with waste milk feeding in animals had 30% growth between 2017–2019. This is due to the possibility of MAP transmission due to feeding of waste milk to calves [ 71 , 72 ]. Leao et al [ 71 ] found that 89.2% of farms enrolled in their study fed waste milk to calves, without pasteurisation except one farm.…”

“…Other factors involved in MAP positivity from feeding waste milk to calves include animal origins (the incidence of MAP in farm with herds from a single origin was 3.5 times higher and 1.9 times higher in farms with herds from multiple origins), and calving area (multiple cow calving increase the risk of MAP positivity by 1.5 compared with single pens) [ 71 ]. Generally, waste milk pasteurisation has been found inadequate to limit MAP transmissions to calves as viable cells (≥1000 MAP cells/mL) were still present after a short pasteurisation period [ 72 ].…”

Early Detection of Mycobacterium avium subsp. paratuberculosis Infected Cattle: Use of Experimental Johnins and Innovative Interferon-Gamma Test Interpretative Criteria

“…Recently, other diseases have been associated with MAP, such as sarcoidosis, Blau syndrome, type 1 diabetes, Hashimoto's thyroiditis, and multiple sclerosis (9,(11)(12)(13)(14)(15)(16). Regarding the transmission sources, MAP may contaminate food for human consumption, such as dairy and meat products, infant formula (17)(18)(19), and water (6,20); and MAP seems to resist pasteurization treatment of milk at 72 • C for 15 s [high-temperature, short-time (HTST) pasteurization] (21)(22)(23).…”

Mycobacterium avium subsp. paratuberculosis Proteome Changes Profoundly in Milk

“…Viable MAP were found in pasteurized milk, cheese, and even in dried milk products such as infant formula [ 12 , 13 , 14 ]. This might have been caused by post-processing contamination, but there is also evidence of MAP being able to survive the pasteurization process [ 15 , 16 , 17 , 18 , 19 ]. The mechanisms behind this tenacity, however, are not fully understood and have been vigorously discussed over the last years [ 8 , 20 ].…”