Food Supply

When investigating an illness outbreak or a death, one of the possibilities that a forensic investigator will assess is the involvement of food. The accidental or malicious contamination of food can be debilitating or, depending on the agent involved, fatal.

A variety of microorganisms or compounds produced by the organisms can contaminate food. As well, inorganic compounds in food can cause illness. Knowledge of the type of food and symptoms displayed can guide a forensic investigator in uncovering the source of the food contamination.

For example, if the nature of the last meal eaten and the symptoms demonstrated by the person affected are known, then forensic examination of the blood for the presence of a particular bacterial toxin may be a prudent step.

Food supplies can be compromised accidentally or deliberately. Since the terrorist attacks on United States soil in September 2001, much concern has focused on the susceptibility of food supplies to deliberate contamination.

Obtaining a strain of bacteria or virus that causes plant or animal diseases is much easier than obtaining a highly infectious human pathogen. Agricultural pathogens can even be obtained from the environment. For example, scraping the surface of infected leaves is sufficient to recover some disease-causing viruses. Both the former Soviet Union and Iraq are known to have experimented with agricultural pathogens.

Microorganisms can also be purchased from supply laboratories. An organization with convincing paperwork would be able to acquire microbes that are not considered to be highly infectious.

The advent of recombinant DNA technology in the 1970s—where a segment of genetic material coding for a protein of interest (i.e., a toxin) can be isolated and spliced into the DNA of a target microbe—holds the potential for the genetic modification of bacteria or viruses that are common in the environment. These genetic versions could spread quickly through the natural world.

Aside from deliberate contamination, food can harbor some types of harmful bacteria such as Clostridium botulinum and Escherichia coli O157:H7, and can cause illness when the food is eaten. Depending on the type of bacteria involved, the mere presence of the bacteria or its toxin may be sufficient to cause illness. Other bacteria need to grow to high numbers in the food before they become noxious. A well-known example is the bacterium Staphylococcus aureus, which has been identified in historical food poisoning outbreaks resulting from contaminated and improperly stored foods such as potato salad.

Different types of microorganisms contaminate different types of food. For example, the aforementioned Clostridium botulinum requires the absence of oxygen. Thus, improperly prepared (usually inadequately heated) canned foods are prone to contamination. The bacterium can produce a potent neurotoxin (a poison that acts upon the nervous system) that can paralyze and even kill a person who eats the contaminated food.

As well, Clostridium botulinum has the ability to form an environmentally resistant protective structure called a spore. The spore form of the organism can persist in a dormant state for very long periods of time. When conditions are more favorable for growth, resuscitation and toxin production can resume.

Following the September 11, 2001, terrorist attacks, the U.S. government moved to strengthen the country's defense against bioterrorism. This initiative culminated in the signing into law, on June 12, 2002, of the Public Health Security and Bioterrorism Preparedness and Response Act of 2002 (the Bioterrorism Act). The act authorized the Secretary of Health and Human Services to protect the nation's food supply. The U.S. Food and Drug Administration (FDA) is the lead agency in initiating the protective measures.

The U.S. measures are aimed at providing a system of accountability. For example, all businesses or growers who sell food for consumption in the U.S. must register with the government. As well, these firms will be required to maintain records of their food handling and processing activities. In the event of a deliberate contamination, this information would allow the source of the contamination to be traced.

The surveillance of food also must include inspection of food entering the country. This involves the manual inspection of foods arriving by air, sea, rail, and surface routes. Inspections typically consist of the visual examination of foods, although the use of portable devices that detect microorganisms or their products is being used experimentally. Other such devices are in the laboratory stage of testing, and have produced accurate results in laboratory settings.

Widespread alerts are often quickly recognized, and contaminated food sources are removed from the food supply, usually before many people will have consumed the contaminated food. Consumer vigilance is an additional important measure to protect the food supply. For example, even if raw produce has been doused with a poison or an infectious microorganism, careful washing will usually remove the threat. Canned foods that are damaged or swollen should be identified and discarded.