Food and Waterborne Illnesses and Laboratory Testing

 Food and waterborne illnesses known as food poisoning are conditions brought about by drinking or eating water or food that’s contaminated by the toxins of microbes they produce. In most cases, the cause of gastrointestinal issues like diarrhea, abdominal pain, vomiting, and nausea. There are lots of non-infectious causes of illnesses instigated by contaminated water and food. At the same time, some microbes are likely to cause infections in other parts of the body apart from the digestive tract. But since most of these are beyond this article’s scope, we will not be covering them here. 

In the U.S., the CDC or Centers for Disease Control and Prevention estimates that about 1 in every six people get sick annually from consuming contaminated beverages or food. Of those, about 128,000 are hospitalized, and about 3,000 die from arising complications. 

Waterborne and foodborne illnesses can affect anybody at any time. However, they tend to be more severe in: 

  • The elderly and very young children, as they may experience severe dehydration 
  • People with compromised or weakened immune systems such as those who’ve had an organ transplant or who have HIV/AIDS. In these subsets, these conditions can be severe and very hard to resolve.  
  • People who suffer from chronic diseases like liver disease, lung disease, heart disease, or diabetes. 
  • Pregnant women – some of these conditions could prove harmful to the developing baby. 

Foodborne illnesses may involve one person or maybe part of a widespread outbreak. Most of these cases come directly from what an individual or individuals have consumed. In some instances, they are passed from one person to another, especially in confined populations like in nursing homes, daycares, or cruise ships. 

Outbreaks tend to occur when more than one person develops symptoms after they have consumed the same drink or food that’s contaminated with the same toxins or microbes. At the same time, they may occur across multiple states or within a locality. Government and public health agencies continuously monitor water and food quality and take swift action to identify, contain, and address the source of an outbreak. However, this task has, in recent days, become harder since a lot more food is being imported to the United States from many foreign countries and as people travel the world. 

When it is suspected that cases of food poisoning are related, public health experts do their best to get the medical histories of the people who’ve been affected and take samples, often stool samples, which they send to public health labs for testing. During outbreaks, people affected are generally advised to share their information about recent travels, the food they have eaten recently (what they have eaten in the last couple of days), symptoms, as well as the type of diarrhea (bloody, watery) they are experiencing. This helps make the process of identifying the root cause much easier.  

Often, samples of suspected sources of contamination also get tested. Public health labs use molecular tests called PFGEs or pulsed-field gel electrophoresis that “fingerprint” DNA to study microbes isolated from individuals who are ill and then search for the pathogens in water or food samples. This allows the labs to identify the common sources of waterborne or foodborne illness quickly. The results from these tests are then entered into a central database known as PulseNet, which is used by federal food safety regulatory laboratories, the CDC, and public and local health agencies to compare DNA fingerprints and identify diseases and illnesses with a common source. If an illness is identified, the necessary steps are taken to ensure the source of the contamination is contained, and the spread of the illness is restricted. 

Causes  

Microbes that contaminate water and food include a range of parasites, bacteria, and viruses. Some of them are found all over the world, and others are regional. At the same time, some are rare, and others are very common. These microbes are responsible for causing symptoms in people who’ve been exposed or those who are more susceptible. Regional bacteria strains might not cause symptoms in people who are accustomed to them. However, when exposed to someone new to them, they may make them sick. While the affected food and water may smell, taste, and look normal, they can cause illnesses that range from self-limited and mild to severe. 

According to data provided by the CDC or Centers for Disease Control and Prevention, the leading cause of waterborne and foodborne illnesses is a virus called Norovirus. This virus is very contagious and easily contaminates water and food and is also easily spread amongst people. 

Several strains of bacteria also feature in the list of contaminants. They include: 

  • Clostridium 
  • Campylobacter 
  • Salmonella 
  • Listeria 
  • Shiga toxin-producing Escherichia coli (STEC) 
  • Yersinia 
  • Vibrio 

The parasite Toxoplasma, listeria, Salmonella, and Norovirus are also considered the most common causes of death caused by food poisoning. While Norovirus only causes a mild illness, the fact that it affects a lot of people makes it one of the top killers. 

Click on one of the links highlighted below for more details on these and other microbes that have been implicated in waterborne and food illnesses: 

  • Bacterial toxins 
  • Viruses 
  • Parasites 
  • Bacteria 

Worth Noting: There are lots of other non-infectious causes of illnesses caused by consuming water or food like poisoning from fish that’s been contaminated with toxins. However, these causes are beyond the focus of this article. 

Bacteria  

  • Salmonella tend to contaminate poultry eggs, raw meat, and other foods. Symptoms of Salmonella poisoning start to develop within 12-72 hours after infection and last for 4 to 7 days. The good thing is that the infection generally resolves with supportive care or even without treatment. However, in people like the elderly or very young, diarrhea may become so bad that they might require hospitalization. For people who are gravely ill, there’s a danger that the illness may spread to their blood, putting them at risk. Such cases need to be addressed promptly to guarantee the safety of the patient. Salmonella serotype Typhimurium and Salmonella serotype Enteritidis are the most common in America. Other cases of Salmonella are travel related. Salmonella typhi, which is quite prevalent in developing countries, is what causes typhoid fever. 
  • Campylobacter is also quite common. Campylobacter jejuni has been implicated in several outbreaks recently. Illnesses causing bloody or watery stools may start to develop 2-5 days after one has been infected and generally last a week. The illness is generally caused by consuming contaminated water, undercooked or raw poultry, or unpasteurized milk or cheese. Complications related to the illness include reactive arthritis and Guillain-Barre syndrome. Cases of Campylobacter related illnesses typically increase in spring and fall. Fortunately, supportive care is usually enough to treat the condition. However, some prolonged or severe cases may require the use of antibiotics. 
  • E. coli – short for Escherichia coli, these are common bacteria found in the digestive tract of animals and humans. While most strains do not cause problems, some produce a toxin called Shiga toxin, which causes bloody diarrhea and potentially serious infections that are easily spread from sources like undercooked meat or one person to the other. These are called Shiga-toxin-producing STEC or E. coli. There is one strain of the bacteria designated O157: H7 that’s quite severe and which has been implicated in a couple of outbreaks. The elderly and very young are usually the most affected by the complications of STEC-related infections such as HUS or hemolytic uremic syndrome. 
  • Listeria monocytogenes – These bacteria are found in unpasteurized milk, soft cheeses, fruits, hot dogs, vegetables, and uncooked meats. The interesting thing about these bacteria is that they still thrive even at refrigeration temperatures. The illnesses caused by this type of bacteria can be quite serious in people with weak immune systems. At the same time, they can be passed from an expectant woman to their developing baby, causing a miscarriage.  
  • Vibrio – Is the most common type of illness-causing bacteria in the world. Vibrio vulnificus, on the other hand, is mostly found in contaminated seafood like raw oysters and in warm seawater. This strain can be quite deadly and is especially a threat to people with weakened immune systems or liver disease. The bacterium Vibrio cholerae is what causes cholera. 
  • Yersinia – This strain of bacteria is found in seafood, unpasteurized milk, and undercooked pork. It’s often linked to chitlins, a dish that’s prepared using the intestines of hogs and which is often served during holidays, which explains why there is an increase of illnesses during winter. The infection is also known to cause reactive arthritis in some people.  
  • Shigella – of the different types of species in existence, there are several that have been known to produce toxins and can cause hemolytic uremic syndrome and reactive arthritis. Shigella dysenteriae is responsible for causing dysentery, severe fever, and bloody diarrhea. 

Viruses  

  • Norovirus – this virus is responsible for most gastroenteritis cases in America, causing over 50 percent of all food poisoning illnesses. The virus is resistant to disinfectant and is extremely contiguous, considering that it is easily spread by touching contaminated surfaces, from person to person, or through contaminated water and food. Norovirus is one of the main causes of food poisoning-related illnesses in restaurants, on cruise ships, and in confined spaces. While most patients feel better in 1-3 days, there is still a risk of serious illness and severe dehydration in the elderly, young children, and people suffering from underlying conditions. People who experience severe dehydration may require hospitalization. Since it is not a bacterium, antibiotics cannot be used to treat infections. 
  • Rotavirus – This virus generally affects children and people with compromised immune systems. It is known to cause severe dehydration and diarrhea. 
  • Hepatitis A – While the number of hepatitis A cases in America is decreasing, infections are still prevalent in some parts of the world. Hepatitis infections can be acquired from shellfish, sewage-contaminated water, and undercooked vegetables and other foods. Luckily, there is a vaccine that helps prevent infection. 

Parasites  

Common parasites that cause waterborne and foodborne illnesses include: 

  • Toxoplasma gondii – Toxoplasma gondii is a single-cell parasite that is ingested when one consumes contaminated water or food, especially undercooked venison, pork, or lamb. It can also be acquired by transmission from pregnant women to their developing babies, handling contaminated cat litter, and, in rare cases, during a blood transfusion or organ transplantation. Most people who get infected aren’t aware of it; when signs and symptoms are present, they tend to be flu-like and mild. In most cases, their immune systems will develop protection against the severe form of the infection. Infants born to infected mothers and people with weakened immune systems are most vulnerable to contracting serious infections. 
  • Giardia duodenalis – This parasite is one of the most common causes of waterborne illnesses. It can also contaminate food and is also easily passed from one person to the other. Infected persons may have a few intermittent symptoms. 
  • Cryptosporidium parvum – Also known as crypto, this parasite can be found in both water and food; infections can become persistent and severe in people with compromised immune systems.  
  • Entamoeba histolytica – this parasite is acquired by consuming contaminated food or water and can be easily spread through contact with infected persons.  

Other possible parasitic causes: 

  • Microsporidia – Infection from contaminated water can lead to chronic diarrhea in people with compromised immune systems. 
  • Cyclospora cayetanensis – found in contaminated water or food. Known to cause watery diarrhea 
  • Cystoisospora belli – found in contaminated water or food. Very common in tropical areas 
  • Taenia saginata and Taenia solium – beef and pork tapeworms from undercooked or raw meat, contaminated water or food  
  • Trichinella spiralis – This parasite is responsible for causing trichinosis. Even though it is rare in the U.S. is now being seen with undercooked wild game and pork; cysts of this parasite have been known to lodge in the muscles of the host. 

Toxins  

Other sources of waterborne and foodborne illnesses include toxins produced by some specific types of bacteria, which include:  

  • Staphylococcus aureus – These bacteria have been known to produce toxins that cause acute symptoms of vomiting and nausea within a couple of hours of consuming food that’s contaminated. 
  • Clostridium botulinum – Mostly found in contaminated food, the toxin produced by these bacteria have been known to cause paralysis and are fatal. Home-canned foods with low acids are the perfect breeding ground for this strain of bacterium. Fortunately, the toxins are easily destroyed by heat. 
  • Clostridium perfringens – this strain of bacteria may contaminate raw poultry and meat, and the associated diseases are linked to consuming food that’s not stored, cooked, or heated properly. The bacteria produce heat resistant spores, which means that once cooked food has cooled down, the bacteria can start growing again. When ingesting, the bacteria produce a toxin that causes acute infections with symptoms of diarrhea and intestinal cramping (but with no vomiting or fever). Symptoms take about 8-12 hours to develop and last for less than 24-hours. Just like with other causes of waterborne and food illnesses, infections can be severe, especially in people with weak immune systems.  

Signs and symptoms  

Viruses and bacteria tend to cause severe illnesses, while parasites cause intermittent or chronic illnesses. Each infection has its own incubation period ranging from several days to several hours after consuming contaminated water or food. At the same time, the length of illness ranges from days to several weeks. 

Common symptoms and signs include:  

  • Vomiting 
  • Nausea 
  • Dehydration 
  • Abdominal pain 
  • Watery diarrhea that is either frequent, intermittent and in some instances, bloody 

Other symptoms and signs include: 

  • Weight loss 
  • Double vision 
  • Fever 
  • Difficulty swallowing 
  • Headache 
  • Muscle weakness; some toxins can cause paralysis 

In more severe cases, an illness may progress to include: 

  • Hemolytic uremia syndrome (kidney failure) 
  • Joint pain, symptoms of reactive arthritis 
  • Sepsis 

It is worth keeping in mind that some cases of waterborne and food illnesses can be fatal. 

Lab Tests 

The initial tests for individuals suspected of having waterborne or foodborne illnesses often start with a stool examination. This may include:  

  • A stool culture – used to detect several commonly encountered bacteria. 
  • Stool antigen tests – includes individual tests capable of detecting Cryptosporidium, Shiga toxin-producing E. coli (STEC), Entamoeba histolytica, or Giardia. 
  • Ova and Parasite (O&P) – generally ordered to spot and identify parasites. 
  • Stool white blood cells (WBC) – this test is used to check the presence of white blood cells in stool. If present, this may indicate a more severe infection involving bacteria or some type of parasite. Special staining tests may be required to identify specific types of parasites in stool samples. 
  • Rotavirus antigen testing – mostly ordered to detect traces of rotavirus. 
  • Individual molecular tests (RT-PCR or reverse transcriptase-polymerase chain reaction) – This test is sometimes performed to detect specific microbes like Norovirus. 
  • G.I. pathogens panel – The G.I. pathogens panel is used to identify the presence of pathogenic (multiple disease-causing) microbes in stool samples. 

Several other tests may be performed as a follow up to or in conjunction with a stool test. Some of these tests include:  

  • Complete blood count (CBC) – A CBC may be ordered to see if the amount of white blood cells in the bloodstream has increased. Increased values are a sign of bacterial infection. 
  • Antibody testing of blood samples for hepatitis A or specific bacteria, sometimes ordered to help confirm a patient’s diagnosis. 
  • Blood culture – A blood culture may be ordered to detect if infections of a bacterial nature have spread into the blood. 

Additionally, specific nutrient media for cultures and specialized techniques may be required to identify and detect some microbes. As such, healthcare practitioners must know potential exposures and request for specialized testing. 

Tests: Stool Culture, Ova and Parasite Exam, Shiga toxin-producing E. coli, Gastrointestinal Pathogens Panel, Comprehensive Metabolic Panel, Complete Blood Count, Blood Culture 

Conditions: Norovirus, Reactive Arthritis, Sepsis, Liver Disease, Travelers’ Diseases, Diarrhea, Guillain-Barr© Syndrome, HIV Infection and AIDS