Microbial Pathogens in Raw MilkBhushan JayaraoExtension Veterinarian
Department of Veterinary ScienceThe Pennsylvania State UniversityUniversity Park
IntroductionMilk and other dairy products are of superior quality and safety
MilkQuality 00 29 49 69 89 99
MilkQuality 00 49 9900 29 49 69 89 99
Pasteurization of milk Milkborne diseases1000
Historical perspective 1900 -1940s: Tuberculosis, Bangs disease, Diptheria, Typhoid fever highly prevalent 1930s: Pasteurization of milk1940-1960s: Eradication of animal diseases (Brucellosis, Tuberculosis)1970s: Few human cases reported1990s: Few human cases still reported Why ?
Improved farm hygiene and milking practices
Improved milk handling and processing technology
Educated consumers and higher consumer awareness on food safety
Newspapers inform public about outbreaks!Milk makes kids sick Salmonella outbreak traced to DAIRY farm ..Milk contains bugs that makes people sick .Scientists say .. Dairy farming ...... Dairy cows .. All infected with dangerous bugsKiller bug on the loose dairy cows responsible
Why do milkborne illnesses occur ?
Faulty pasteurization of fluid milk Defective pasteurizer -- less likely
Post-pasteurization contamination of milk and milk products-- likely
Raw milk consumptionRural communities with access to raw milk Holistic / new age / back to nature - city folks ?Visitors on farms raw milk products
Highly prevalent in the rural communities
Rohrbach & others: 1991, Eastern Tennessee - 34.9%Jayarao & others: 1997, South Dakota & Minn.- 60%Jayarao & others: 1998, Pennsylvania - 54%
How prevalent is consumption of raw milk ?
The Epidemiology of Raw Milk - Associated Foodborne Disease Reported in the United States 1973-1992 [ Headrick and others, Am. J. Pub. Hlth. 88, 1219-1221; 1998]Results of the study 46 raw milk associated outbreaks reported were during the study period40 outbreaks (87%) occurred in states where the intrastate sale of raw milk was legalConclusions of the study Consumption of raw milk remains a preventable cause of foodborne disease outbreaksLegal to sell raw milkWA, CA, OR, MO, ID, NV, AR, NM,TX, UT, SD, NE, KS, OK, MN, MO, AR, OH, PA, NY, ME, VT, NH, CONN, MA SC,IL, RI, WIIllegal to sell raw milkND, WY, CO, IA, MI, IN, KY, TN, LA, AL, GA, FL, NC, AL, PR, WV, VA, MD, NJ, HA, DE, MD
Health risks associated with raw milk ?Several reports on foodborne outbreaks due to consumption of raw milk Escherichia coli O157:H7Salmonella typhimurium DT104Campylobacter jejuniListeria monocytogenesYersinia entercoliticaSalmonella spp.
How do pathogens get into raw milk ?
How do Pathogens gain access to a farm ?Replacement calves trucksheifer/ cows birds /pests feed water visitors Most importantsources ofinfection
Other routes of entry
Putting it all together !
Salmonella Occur in humans, warm and cold blooded animals, food and environmentPathogenic to humans and many animalsCauses typhoid, enteric fevers, gasteroenteritis and septicaemiaMore than 2200 types of SalmonellaPrevalence in bulk tank milk19874.7%*USA19880.2%United Kingdom 19882.9%Canada19920.16% Ireland19928.9%USA 19950.36%England & Wales19976.1%USA ...19980.17%CanadaLight MicroscopeElectron Microscope
Salmonella Typhimurium DT 104Emerging foodborne pathogenDetected in several countriesWhy is DT 104 of concern ?Multiple antibiotic resistanceAmpicillinChloramphenicolStreptomycinSulfonamidesTetracyclineDT 104 has been isolated from; poultry, swine, cattle and wild animals, and from bulk tank milk
Campylobacter jejuniInhabitant in the reproductive tract, intestine, and oral cavity to humans and animalsExcreted in large numbers in feces1983- Campylobacterosis associated with raw milk consumption in PA Prevalence in bulk tank milk
Escherichia coliOccur as normal flora in the lower part of intestine of warm blooded animalsToxin producing strains of E. coli are important agents of food-borne illnessesEmerging pathogen E. coli O157:H7; dairy cattle considered as reservoirs.Prevalence of enterotoxigenic E. coli in bulk tank milk
19891.4%Canada19973.9%Germany199712.3 % Canada19973.8%USA ...19980.87%Canada
Yersinia enterocoliticaOccur in a broad spectrum of habitats including man, animals, rodents, birds, soil, water, dairy products and other foods. Yersinia enterocolitica causes chronic diarrhea and severe septicaemiaPrevalence of Y. entercolitica in BTM197822%Ontario Canada197818%Ontario Canada198181%France198437%Italy199215.1%USA19976.1%USA.
Listeria monocytogenesWidely distributed in the environmentListeria monocytogenes pathgoenic to humans and animalsSeveral reported outbreaks following consumption of raw milkPrevalence of L. monocytogenes in bulk tank milk
19874.2%USA19881.3%Canada19885.4%Canada19905.2%South Africa19924.9%Ireland19924.1%USA19955.1%England and Wales19974.6%USA...19982.7%Canada
Why do people consume raw milk ?
Access to raw milkLess access to pasteurized milkDrinking raw milk practiced over timeA notion that raw milk is better than pasteurized milk
Should one discontinue drinking raw milk ?Yes ! If you are,Concerned about pathogens in raw milk such as Salmonella DT 104 or E. coli O157:H7Elderly / young / immunocompromised/ expectant mothersGenetic type HLA-27, which makes you more disposed to reactive arthritis if exposed to foodborne pathogens such as Campylobacter jejuniGuilliame Barres syndromeConcerned about long term effects on health Can we pasteurize milk in our home ?Yes ! you can,Nasco- Safeguard Home Pasteurizer ( ~ $ 200)