Which pathogen was the most common cause of outbreaks from unpasteurized milk between 1990-2006?

• A. Campylobacter
• B. Listeria
• C. Salmonella
• D. Shigella

Answer: (A)

Unpasteurized milk can harbor enteric bacteria from the cattle, and some organisms are more commonly transmitted through dairy than others. In the 1990–2006 period, Campylobacter was the pathogen most frequently linked to outbreaks from raw milk because it is a common inhabitant of the bovine gut and easily contaminates milk during milking or handling. It also has a relatively low infectious dose and can persist in refrigerated products long enough to cause illness, making raw-milk outbreaks with Campylobacter more common than those caused by other pathogens.

Listeria, while a serious concern with unpasteurized dairy and capable of growing at refrigeration temperatures, contributed fewer outbreaks in this interval. Shigella and Salmonella can be involved in dairy-associated illnesses, but their outbreaks from raw milk were less common compared with Campylobacter during these years.