Microbial Pathogens in Raw Milk

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Microbial Pathogens in Raw Milk

• Bhushan Jayarao
• Extension Veterinarian
• Department of Veterinary Science
• The Pennsylvania State University
• University Park

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Introduction

• Milk and other dairy products are of superior
  quality and safety

Milk Quality
00 29 49 69 89 99
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Milkborne diseases
1000 500 250
Pasteurization of milk
Milk Quality
00 29 49 69 89 99
00 49 99
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• Historical perspective
  
  
• 1900 -1940s Tuberculosis, Bangs 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 ?
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Improved farm hygiene and milking
practicesImproved milk handling and processing
technologyEducated consumers and higher
consumer awareness on food safety
Still.
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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 bugs Killer bug on the loose dairy
cows responsible
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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

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How prevalent is consumption of raw milk ?

• 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

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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
Legal to sell raw milk WA, 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,
WI Illegal 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

• 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

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• Health risks associated with raw milk ?
• Several reports on foodborne outbreaks due to
  consumption of raw milk
• Escherichia coli O157H7
• Salmonella typhimurium DT104
• Campylobacter jejuni
• Listeria monocytogenes
• Yersinia entercolitica
• Salmonella spp.

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How do pathogens get into raw milk ?
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How do Pathogens gain access to a farm ?
Most important sources of infection
Replacement calves
trucks heifer/ cows
birds /pests feed water
visitors
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Other routes of entry
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Putting it all together !
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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
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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

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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 USA 1983 1.5 USA 1986 4.8 USA 1988
5 Netherlands 1988 6 UK 1988 4 USA 1992 12.
3 USA 1997 9.2 USA ... 1998 0.47 Canada
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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 O157H7 dairy cattle
  considered as reservoirs.
• Prevalence of enterotoxigenic E. coli in bulk
  tank milk

1989 1.4 Canada 1997 3.9 Germany 1997 12.3
Canada 1997 3.8 USA ... 1998 0.87 Canada
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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 BTM

Natural hosts
1978 22 Ontario Canada 1978 18 Ontario
Canada 1981 81 France 1984 37 Italy 1992 15.1 U
SA 1997 6.1 USA.
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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 USA 1988 1.3 Canada 1988 5.4 Ca
nada 1990 5.2 South Africa 1992 4.9 Ireland
1992 4.1 USA 1995 5.1 England and
Wales 1997 4.6 USA... 1998 2.7 Canada
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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

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• Should one discontinue drinking raw milk ?
• Yes ! If you are,
• Concerned about pathogens in raw milk such as
  Salmonella DT 104 or E. coli O157H7
• 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 Barres syndrome
• Concerned about long term effects on health
• Can we pasteurize milk in our home ?
• Yes ! you can,
• Nasco- Safeguard Home Pasteurizer ( 200)

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