The Perils of Raw Milk

Linda K. Gaul, PhD, MPHEpidemiologist, Infectious Disease Control Unit

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History of Raw Milk Consumption, Illnesses, and Regulation

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History of Pasteurization and Milk-Associated Illnesses

• Pasteur worked on process to prevent wine spoilage• Pasteurization is the heat treatment of food to kill bacteria

• Early 1900s, pasteurization used for milk• Fewer milkborne infections were noted• In the 1930s, milk pasteurization was mandated in many

large cities• In 1938, milkborne outbreaks made up ~25% of

outbreaks due to contaminated food and water

Hall, C.W and Trout, GM. Milk Pasteurization; AVI Publishing Company; 1968.LeJeune, J.T. and Rajala-Schultz, P.J. CID. 2009;48:93-100.

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Pathogens Historically Associated With Raw Milk

• Campylobacter sp.• Shiga-toxin producing Escherichia coli (STEC)

• Including E. coli O157:H7

• Salmonella sp.• Listeria monocytogenes• Staphylococcus aureus• Yersinia enterocolitica• Mycobacterium bovis - Bovine tuberculosis• Brucella melitensis

Dairy animals are reservoirs for these organismsToday, M. bovis and B. melitensis are controlled by nationwide eradication

programs for cattle herds. Occasionally, infected cattle are still found.

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History of Pasteurization and Milk-Associated Illnesses, continued

• By 1950, pasteurization was standard for commercial US milk supply• Nearly all pasteurized milk today is heated to

161oF for 15 seconds

• In 2000, milkborne outbreaks made up <1% of outbreaks due to contaminated food and water

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Achievements in Public Health, 1900-1990Safer and Healthier Foods

Morbidity and Mortality Week Report

October 15, 1999

“Once the sources and characteristics of foodborne diseases were identified--long before vaccines or

antibiotics--they could be controlled by handwashing, sanitation, refrigeration, pasteurization, and pesticide

application.”

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Regulation of Raw Milk Sales

• In 1987, FDA prohibited interstate sales of unpasteurized milk• The FDA does not regulate intrastate sales

• Each state regulates intrastate unpasteurized milk sales• States vary in the type of raw milk sales that are allowed, if any

• The sale of raw milk is illegal in 20 states• 30 states allow the sale of raw milk in certain settings

• 13 allow retail store sales• 14 allow on-farm sales only (including Texas)• 2 states allow sales by prescription only• 1 state allows sales through purchase of “cow shares”

• Licensing and requirements for raw milk sales vary by state, where allowed

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Status of Raw Milk Sales, 2008

Centers for Disease Control and Prevention (CDC), October 2009

Milk Consumption Preferences 2002-2003 FoodNet Survey

Consumer 23 times more likely to drink pasteurized milk

U.S. Census Bureau, http://www.census.gov/popest/estimates.html9

Estimated US population 288 million in 2002-03

Survey pop. Estimated US

Milk type drinking pop. drinking (#)

Any kind 81.6% 248,000,000

Unpasteurized 3.5% 8,680,000

Milk consumption during the past 7 days:

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Epidemiology of Illnesses Associated with Raw Milk Consumption

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How Illnesses are Associated with Specific Foods

• Sporadic cases are only rarely linked to a specific food vehicle

• Outbreak data provide the best evidence for links to food vehicles

• Milkborne outbreaks have been associated with:• Unpasteurized milk and milk products• Inadequately pasteurized or post-pasteurization

contaminated milk and milk products

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Milk-Associated Outbreaks,Scotland, 1980-2004

Sharp. J Med Micro. 1989. 29:239-242.; Food Standards Agency, 5/11/2009.

0

5

10

15

20

25

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1980-1982 1983-1985 1986-1988 1989-2004

# of Outbreaks

1983 Legislation Prohibits

Sale of Raw Milk

1986 Legislation Prohibits

payment to farm workers

in raw milk

↓ ↓

1424

Cases 126

Cases

45

Cases

Outbreaks from

1986-2004 limited

to farm families

Raw Milk Associated Outbreaks, US, 1973-1992

• 46 outbreaks reported from 21 states• 1733 cases

• 40 (86%) occurred in states where raw milk sale was legal at time of outbreak

• 6 (14%) occurred in states where raw milk sale was not legal at time of outbreak

• 6 times as many outbreaks in states where raw milk sales were legal

Headrick, et al. 1998 AJPH.88:1219-1221

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Raw Milk Associated Outbreaks, US, 1998-2007

Center for Disease Control and Prevention (CDC): October 2009

• 41 (80%) occurred in states where raw milk sale was legal at time of outbreak• 10 (20%) occurred in states where raw milk sale was not legal at time of outbreak•4 times as many outbreaks in states where raw milk sales were legal

Raw Pasteurized**Milk Milk

51 12

1054 2213

57 25

Number of Outbreaks

Number of Cases

Number of Hospitalizations**The pasteurized milk outbreaks were traced back to attempted pasteurization that failed or contamination after pasteurization

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Reported OutbreaksAssociated with Raw Milk 1998-2007

National Association of State Departments of Agriculture Raw Milk Survey April 2008; CDC, October 2009

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Pathogens in Raw Milk Associated Outbreaks, US, 1998-2007

Center for Disease Control and Prevention (CDC): October 2009

Raw Pasteurized**Milk Milk 51 12

Campylobacter Spp 42 3Escherichia coli O157:H7 7 0Listeria monocytogenes 0 1Salmonella Spp 2 3Unknown agent 0 5

Number of Outbreaks

**The pasteurized milk outbreaks were traced back to attempted pasteurization that failed or contamination after pasteurization

Outbreak Pathogens

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Texas Outbreaks Associated with Raw Milk

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Texas Outbreaks Associated with Raw Milk or Raw Milk Cheese*

• 2000 Campylobacteriosis outbreak• 2 cases• Sampled raw goat milk at a conference• Included in 1998-2007 outbreak summary slide

• 2003-2009 Listeriosis outbreak• 46 cases, 9 deaths

• 29 mother-baby sets (5 miscarriages, stillbirths, infant deaths)• 17 immonocompromised persons (4 deaths)

• Case-patients consumed unpasteurized queso fresco (cow milk)• Cheese produced in Mexico• Cheese carried legally into US• Cheese sold illegally in US

• NOT included in 1998-2007 summary slide

*Cheeses not included in other outbreak information

Campylobacteriosis Outbreaks Associated with Raw Milk,

Youth Activities, US, 1981-1990

• CDC survey of 50 states, Puerto Rico

• Youth activities: School field trips to dairy farms, other

• 20 outbreaks, 11 states• 1013 youths, adults drank raw milk, 458 ill

• Attack rate 45%• 12 known hospitalizations, no deaths• 70% of outbreaks with children K-3rd grade

• Only 60% of outbreaks reported to CDC• Wood, et al. 1992. JAMA. 268:3228-3230.

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Nutritional and Other Health Considerations, Raw vs. Pasteurized Milk

Claimed Advantages of Unpasteurized Milk over Pasteurized

Milk: Are These Real?

• There are no scientific studies reported in peer-reviewed literature that show any advantage of unpasteurized milk over pasteurized• Some raw milk advocates claim that certain beneficial

proteins and other chemicals are degraded substantially during pasteurization

• Milk is not a significant source for some of these chemicals, such as vitamin C

• Only ultra-high temperature pasteurization destroys many other chemicals

• Unpasteurized milk always carries with it the risk of illness caused by pathogens

• The nutrients for which milk is an important source are not destroyed or altered by pasteurization• Calcium, protein

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Characteristics of Human Breast Milk and Animal Milk

Human breast milk• Mother produces antibodies,

other protective substances against pathogens in her environment

• Milk is sterile• Unless mother has an infection

Unpasteurized animal milk• Animals produce antibodies,

other protective substances against pathogens in their environment

• Milk is not sterile, • Even if animals are healthy

Newman. 1995. SA:273:76-79; Potter, 1984. JAMA:252, 2048-2052

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Characteristics of Human Breast Milk and Animal Milk

Human breast milk• Substances suppress

harmful bacteria and block their absorption, promote beneficial bacteria

• Benefits last only ~3 months, when baby’s immune system becomes more mature

Unpasteurized animal milk• Substances may suppress

harmful bacteria and block their absorption, promote beneficial bacteria

• Any benefits would last only ~3 months, when baby’s immune system becomes more mature

Newman. 1995. SA:273:76-79; Potter, 1984. JAMA:252, 2048-2052

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American Academy Of PediatricsPosition Statement

“Prevention of disease in children is one of the Academy’s highest priorities. Raw milk is known to transmit infectious diseases, and pasteurization is known to minimize risk. Raw milk has no benefits that would justify any increase in risk to children. The Academy supports legislation efforts at both the state and national levels that mandate pasteurization of all dairy products.”

Bradley et. al. December 2008. AAP News. Volume 29

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Regulation of Raw Milk in Texas

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Current Raw Milk Regulations In Texas

• Farms selling Grade “A” Raw for Retail Milk must be licensed with DSHS• However, DSHS is aware of some unlicensed farms

• The consumer can purchase raw milk from a farm that has a Grade “A” Raw for Retail permit

• Grade “A” Raw for Retail dairies have same requirements as the dairies that sell milk to be pasteurized, except• Additional requirements for coliform and pathogen

testing• Milk must be stored at or below 45 ºF until sold

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Licensed Retail Raw Milk Farms

35 Licensed Grade “A” Raw for Retail Dairies

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“Consumption of raw milk remains a preventable cause of foodborne disease outbreaks.”

Headrick, et al. 1998 AJPH.88:1219-1221

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Acknowledgements

Julie Loera, Division of Regulatory Affairs, DSHSFrank Borden, Division of Regulatory Affairs, DSHS Gene Wright, Division of Regulatory Affairs, DSHSMaricela Montoya, WIC Clinical Services, DSHSTracy Hayward, Division of Prevention and Preparedness, DSHS