FOOD SAFETY & FOOD ANIMALS

DAVID R. HENNING

DAIRY SCIENCE DEPARTMENT

SOUTH DAKOTA STATE UNIVERSITY

May 17, 2001

Food Safety & Food Animals

• Diseases - Human Prion Diseases, TSE,BSE, CWD

• Specific Risk Materials

• Food Safety - BSE

• Zoonoses– E. coli O157:H7

– Listeriosis

– Others

Human Prion Diseases

• Diseases of human that affect primarily the nervous system.

• These diseases are characterized by presence of microscopic vacuolization of the brain tissue, called spongiform degeneration, and of an abnormal form of a protein, called prion protein, which is a normal cell surface component in brain and other tissues.

Human Prion Diseases - Cont..

• Abnormal prion protein is resistant to digestion with enzymes that breakdown normal proteins, and accumulates in the brain.

• Abnormal prions provide a template for normal prions to assume abnormal prion properties. No genes have been linked to production of the abnormal prions

Human Prion Diseases - Cont..

• Sporadic - Creutzfeldt-Jakob Disease (CJD), Familial insomnia (FI)

• Familial - Creutzfeldt-Jakob Disease (CJD), Fatal Familial Insomnia (FFI), Gerstmann-Straussler-Scheinker Syndrome (GSS)

• Acquired - Creutzfeldt-Jakob Disease (CJD), Kuru, new variant Creutzfeldt-Jakob Disease (nvCJD)

nvCJD

• Nearly 100 confirmed deaths from nvCJD

• More than half of the UK deaths <30 years old. Median age is 27.5, Oct 2000.

• <5 cases per 1 billion from CJD in USA

• Prions from nvCJD patients and BSE agents are similar, and are distinct from prions obtained from familial CJD patients

FOOD SAFETY ASSESSMENT

• From the Centers for Disease Control and Prevention– “It is extremely unlikely that BSE would be a

foodborne hazard in this country.”

– “The risk of infection with the BSE agent among travelers to Europe is extremely small, if it exists at all.”

Food Safety Assessment

• USDA has contracted with the Harvard Center for Risk Analysis - Harvard School of Public Health to analyze the potential for BSE in the United States.

SAFE CATTLE PRODUCTS

• Opinion of WHO Expert Consultation - 1996– “Bovine milk from clinically healthy cows and

products made from it can be safely consumed.”

• Milk and muscle meats have not transmitted the infective agent in any published studies.

Specific Risk Materials - MAFF

• Tissues of cattle, sheep, and goats which are known to, or might potentially, harbor detectable BSE infectivity in infected animals

• Cattle– Skull including brains and eyes, tonsils, spinal

cord of animals >12 months

– Intestines from duodenum to rectum of bovines of all ages.

Specific Risk Materials - Cont..

• Cattle (UK and Portugal)– Entire head, excluding tongue, thymus, spleen

and spinal cord of animals > 6 months– Vertebral column (including dorsal root ganglia

of animals > 30 months

Specific Risk Materials - Cont..

• Sheep and Goats (EU)– Spleen of all animals– Skull including brains and eyes, tonsils, spinal

cord of animals >12 (or have a permanent incisor erupted through the gum)

– Any material still attached to the above materials after dissection for the carcass and any animal matter which comes into contact with it after is has been taken off the carcass

Specific Risk Materials - Cont..

• UK Food and Animal Feed restriction– Requires same controls on SRM on imported

materials as on domestic. – Accompanied by a certificate confirming that

they are SRM-free or that they are from animals born, reared and slaughtered in Australia or New Zealand.

Specific Risk Materials - Wildlife

• WY - Suggested Precautions– Don’t shoot animals acting abnormally or look sick– Wear rubber or latex gloves to field-dress and wash

hands after contact– In CWD areas, minimize contact with a dead deer’s

brain and spinal cord– Don’t eat deer brains or spinal cord– Bone our deer, discard brain, spinal cord, eyes,

spleen,and lymph nodes.

Ruminant Feeding Rules

• The Specific Risk Materials are called Prohibited Materials in the US.

• The U.S. FDA has banned these mammalian proteins in feeds for ruminants.

• The rules for labeling feeds by facilities which produce, handle or store ruminant feeds will be discussed by Secretary Gabriel.

Foods Safety Aspect of Prohibited Feed

• GAO opinion in “Safety of Animal Feed”– “BSE is one of the most significant threats to

human health that can result from unsafe animal feed.”

Best Business Practices

• American Meat Institute proposed that– Producers certify that livestock meets all U.S.

FDA requirements regarding the BSE feed ban.– Producers also certify that animal drugs were

used legally on the livestock being offered for sale.

• On-Farm Safety Certificates

Zoonosis

• A disease transmissible under natural conditions from vertebrate animals to humans.– Salmonellosis– Listeriosis– Undulant Fever– Trichinosis– Tuberculosis– Escherichia coli O157:H7

Food Safety and Products from Food Animals

• 85% of food-borne illness can be attributed to fruits, vegetables, seafood and cheese

• Audits International has shown that food safety practices in the home are no better than practices in foodservice establishments– 115 households evaluated– 74% of homes made at least one critical

violation

Food Safety and Products from Food Animals

• Six most frequent violations - Audits Int’l– Neglected Handwashing– Improper Food Preparation Techniques– Cross-Contamination– Improper Cooling of Leftovers– Finished Internal Cooking Temps Too Low– Improper Chemical Labeling

Escherichia coli O157:H7

• “Hamburger” disease, a variety of sources

• USA E. coli O157:H7 illness statistics– 73,000 cases (est.)– 2000 hospitalizations– 60 deaths

• Several outbreaks among children visiting fairs, farms, and petting zoos

Escherichia coli O157:H7

• Study in South Dakota – Surveyed cattle slaughtered in facilities

inspected by SD AIB– Ground beef sampled in the same facilities– Survey in all sectors of the state– 140 animals tested - fecal swab only– 126 samples of ground beef tested

Escherichia coli O157:H7

• Results from cattle and ground beef– Over 1,400 cultures of Escherichia coli– No E. coli O157:H7– 167 cultures had a gene for producing Shiga

toxin

Escherichia coli O157:H7

• Other concerns about E. coli O157:H7– Has ability to adapt to acid resistance– Many sources other than hamburger

• Raw milk

• Cider

• Fruit juices

• Dry cured sausages

• Sprouts

Listeria monocytogenes

• Ubiquitous microorganism in production agricultural areas

• Particularly deadly for persons at risk– Fatality rate is above 30%– Young– Old– Immunocompromised

Listeria monocytogenes

• Dairy Products were focus in 1980’s

• Smoked fish industry has continuing problems

• Processed meats have had several serious outbreaks in late 1990’s

Salmonella species

• Salmonella species inhabit the intestinal tract of birds, reptiles, farm animals, humans and insects.

• There are over 2,400 serotypes

• Salmonella species found in 60% of the meat and bone meal in 1990 in a poultry feeding operation.

Salmonella species

• Salmonella species in poultry feed has been shown to infect poultry products that caused human illness.

• Efforts to limit Salmonella infections have been ongoing since the 1950’s.

• A large outbreak in 1994 resulted in an estimated 224,000 illness from ice cream distributed throughout the U.S.

Raw Milk

• A survey of the milk supply for a Chicago dairy in 1986-1988 showed that 8 to 15% of raw milk samples had Salmonella species.

• Other surveys indicated about 4% of the samples contain Listeria monocytogenes

• Other pathogens are also present - E. coli O157:H7, Campylobacter, etc.

Raw Milk

• Consumption of raw milk in the upper Midwest is still prevalent.

• Advocates of raw milk cheeses are asking the FDA to continue to allow raw milk for certain varieties.

• Consumption of raw milk is a voluntary risk for a farm family.

Summary

• There have been no cases of BSE in the U.S.

• There have been no cases of nvCJD in the U.S.

• Human prion diseases caused by BSE is extremely unlikely in the U.S.

• Ruminant animal feeds with prohibited materials could be a threat to human health.

Summary - Cont.

• Food animals are the source of many microorganism capable of causing human food-borne illness.

• Households need to practice food safety principles to reduce incidences of food-borne illness.