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)