Microbial Pathogens in Raw Milk
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Transcript of Microbial Pathogens in Raw Milk
Microbial Pathogens in Raw Milk
Bhushan JayaraoExtension Veterinarian
Department of Veterinary Science
The Pennsylvania State University
University Park
Introduction
Milk and other dairy products are of superior quality and safety
MilkQuality
00 29 49 69 89 99
MilkQuality
00 49 99
00 29 49 69 89 99
Pasteurization of milk
Milkborne diseases
1000
500
250
Historical perspective 1900 -1940s: Tuberculosis, Bang’s disease, Diptheria, Typhoid fever highly prevalent
1930s: Pasteurization of milk
1940-1960s: Eradication of animal diseases (Brucellosis, Tuberculosis)
1970s: Few human cases reported
1990s: 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
Still……………….
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 consumption Rural 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 period 40 outbreaks (87%) occurred in states
where the intrastate sale of raw milk was legal
Conclusions of the study Consumption of raw milk remains a
preventable cause of foodborne disease outbreaks
Legal 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 milk
ND, 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:H7
• Salmonella typhimurium DT104
• Campylobacter jejuni
• Listeria monocytogenes
• Yersinia entercolitica
• Salmonella 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 environment Pathogenic to humans and many animals Causes typhoid, enteric fevers, gasteroenteritis and
septicaemia More than 2200 types of Salmonella Prevalence in bulk tank milk
1987 4.7%* USA 1988 0.2% United Kingdom 1988 2.9% Canada 1992 0.16% Ireland 1992 8.9% USA 1995 0.36% England & Wales 1997 6.1% USA ……... 1998 0.17% Canada
Light Microscope
Electron Microscope
Salmonella Typhimurium DT 104 Emerging foodborne pathogen Detected in several countries Why is DT 104 of concern ?
Multiple antibiotic resistance Ampicillin Chloramphenicol Streptomycin Sulfonamides Tetracycline
DT 104 has been isolated from; poultry, swine, cattle and wild animals, and
from bulk tank milk
Campylobacter jejuni Inhabitant in the reproductive tract,
intestine, and oral cavity to humans and animals
Excreted in large numbers in feces 1983- Campylobacterosis associated
with raw milk consumption in PA Prevalence in bulk tank milk
1982 0.9% USA1983 1.5% USA1986 4.8% USA1988 5%Netherlands1988 6% UK1988 4% USA1992 12.3% USA1997 9.2% USA ……...1998 0.47% Canada
Escherichia coli Occur as normal flora in the lower
part of intestine of warm blooded animals
Toxin producing strains of E. coli are important agents of food-borne illnesses
Emerging pathogen E. coli O157:H7; dairy cattle considered as reservoirs.
Prevalence of enterotoxigenic E. coli in bulk tank milk
1989 1.4% Canada1997 3.9% Germany1997 12.3 % Canada1997 3.8% USA ……...1998 0.87% Canada
Yersinia enterocolitica Occur 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 septicaemia
Prevalence of Y. entercolitica in BTM1978 22% Ontario Canada1978 18% Ontario Canada1981 81% France1984 37% Italy1992 15.1% USA1997 6.1% USA….
Natural hosts
Listeria monocytogenes Widely distributed in the environment Listeria monocytogenes pathgoenic
to humans and animals Several reported outbreaks following
consumption of raw milk Prevalence of L. monocytogenes in
bulk tank milk
1987 4.2% USA1988 1.3% Canada1988 5.4% Canada1990 5.2% South Africa1992 4.9% Ireland1992 4.1% USA1995 5.1% England and Wales1997 4.6% USA...1998 2.7% Canada
Why do people consume raw milk ?
Access to raw milk Less access to pasteurized milk Drinking raw milk practiced over
time A 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:H7
Elderly / young / immunocompromised/ expectant mothers
Genetic type HLA-27, which makes you more disposed to reactive
arthritis if exposed to foodborne pathogens such as Campylobacter jejuni
Guilliame Barre’s syndrome
Concerned about long term effects on health
Can we pasteurize milk in our home ? Yes ! you can,
Nasco- Safeguard Home Pasteurizer ( ~ $ 200)