Food or Water-borne illness
Page content: Victorian statutory requirement | Infectious & other causative agents | Identification | Incubation period | Public health significance and occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility and resistance | Control measures | Outbreak measures | Additional sources of information | Common food- or water-borne pathogens
Victorian statutory requirement
Two or more related cases of suspected food or water-borne illness must be notified within 24 hours of diagnosis.
School exclusion: for most gastrointestinal illnesses children should be excluded from school or childcare until at least the diarrhoea has ceased.
Infectious & other causative agents
The most frequent causes of food or water-borne illnesses are various bacteria, viruses and parasites. Refer to specific sections for detail on the more common agents.
Non-infective agents:
- heavy metal poisoning, including, cadmium, copper, lead, tin and zinc
- fish toxins that are present in some shellfish or fish like paralytic shellfish poisoning or ciguatera
- plant toxins which occur naturally in some foods such as toxic fungi and green potato skins
- toxic cyanobacteria (blue green algae) overgrowth in water.
Bacteria:
- toxin produced in food:
- Staphylococcus aureus
- Clostridium botulinum
- Bacillus cereus
- damage to gut wall and/or systemic infection:
- Salmonella spp.
- Shigella spp.
- Clostridium perfringens
- Campylobacter spp.
- E. coli.
- Helicobacter pylori
- Vibrio cholerae/V. parahaemolyticus
- Yersinia enterocolitica
- S.typhi/Paratyphi
- Brucella spp.
- Listeria monocytogenes
Viruses:
- Hepatitis A and E viruses
- Noroviruses and other small round structured viruses (SRSV)
- Rotavirus
Parasites:
- Cryptosporidium spp.
- Entamoeba histolytica
- Giardia lamblia
Identification
Clinical features
Symptoms vary with the causative agent and range from slight abdominal pain and nausea to retching, vomiting, abdominal cramps, fever and diarrhoea. Fever, chills, headache, malaise and muscular pains may accompany gastrointestinal symptoms. Vomiting, with or without diarrhoea,abdominal cramps and fever are common symptoms of viral disease or staphylococcal intoxication. Certain food-borne illnesses can present with meningitis or septicaemia (listeriosis) or with neurological symptoms (paralytic shellfish poisoning, botulism).
Severity depends on host and agent characteristics and the infectious dose. Hospitalisation and death may occur due to acute dehydration, metabolic acidosis and subsequent organ failure.
The duration of illness varies from hours (24/48 hours in viral and staphylococcal infections) to days and even weeks in salmonellosis and campylobacteriosis.
Method of diagnosis
Diagnostic methods vary according to the type of infective agent:
- bacteria can be isolated from faeces or blood or by detection of toxin
- parasites can be isolated by microscopy of fresh or appropriately preserved faeces
- viruses can be isolated by stool electron microscopy (EM), immune EM or paired sera from patients to detect seroconversion to a virus
- chemicals can be isolated by serological detection of implicated compounds.
Advice regarding specific tests should be sought from laboratories with expertise in the identification of gastrointestinal pathogens and chemical agents.
Incubation period
Incubation periods are typically short for toxin-producing bacteria and longer for others.
Public health significance & occurrence
Food and water-borne diseases are thought to be the most common of all acute illnesses. However a large proportion of disease is not detected, as many people will not seek health care with mild illness. Occurrence is worldwide and the incidence varies from country to country.In recent years the detection of outbreaks of viral origin, especially noroviruses, has been increasing.
Reservoir
- Soil, dust, cereals
- Bacteria and parasites: fish, birds, reptiles, wild and domestic animals
- Viruses: humans
Mode of transmission
Transmission is predominantly via the faecal-oral route or ingestion of contaminated food and water sources. Transmission via aerosols (produced during profuse vomiting) has been implicated in outbreaks involving viral pathogens.
Period of communicability
Communicable periods for food and water-borne illnesses depend on the causative agents. Viruses are generally communicable during the acute phase and up to two days after recovery while bacteria are generally communicable during the acute diarrhoeal stage. For parasites refer to relevant sections in this book.
Susceptibility & resistance
With most infections everyone is susceptible, however sporadic disease is more often detected in young children, the elderly or immunocompromised people. This is in some part due to the health care seeking behaviours of those caring for patients in these categories.
Control measures
Preventive measures
Prevention of the contamination of potable water is very important. Contaminated water should be treated by adequate filtration and disinfection or by boiling.
Avoiding contamination of food is also important. This can be achieved by:
- providing raw materials of better microbiological quality
- educating food handlers about proper food processing, preparation,storage and in personal hygiene
- adopting the following 'Ten golden rules for safe food preparation' developed by WHO:
- choose food processed for safety
- cook food thoroughly
- eat cooked food immediately
- store cooked food carefully
- reheat cooked food thoroughly
- avoid contact between raw foods and cooked foods
- wash hands repeatedly
- keep all kitchen surfaces meticulously clean
- protect food from insects, rodents, and other animals
- use pure water
Incorporation of HACCP (Hazard Analysis Critical Control Point) systems is important for good manufacturing practices for food industries.
Vaccines are currently available for cholera and hepatitis A (refer to relevant sections).
Control of case
Control of the case ranges from supportive treatment and rehydration to hospitalisation.
Cases due to infection need exclusion from food handling, schools and children's services centres until after the diarrhoea has ceased.
Health care workers need exclusion if employed in an area with high risk patients, such as special care nurseries or nursing homes, until after the diarrhoea has ceased.
Control of contacts
Control of contacts includes:
- prevention of further ingestion of contaminated food or water
- surveillance of contacts who are food handlers if required
- withdrawal of implicated food (if in retail outlets) from sale.
Control of environment
Investigate water sources or place of manufacture or preparation of incriminated food and institute corrective action.
Outbreak measures
Food and water-borne outbreaks are usually detected following the onset of illness in a group of people who have shared a common meal. The primary objectives of outbreak control are the rapid identification of the causative agent through epidemiological, environmental and laboratory investigations and prevention of further disease by destruction or denaturation of the source.
International measures
International outbreaks are increasingly being recognised, primarily due to the increased trade in food and agricultural products worldwide. Food and water-borne pathogens and contaminants have been identified as potential biological terrorism agents. Cases of rare diseases like botulism should be investigated immediately. Some diseases require notification to the World Health Organization, like cholera.
Quarantine of suspected sources or halting international trade should be coordinated through Food Standards Australia New Zealand.
Additional sources of information
Food Standards Australia New Zealand
Common food or water-borne pathogens
| Causative agent | Incubation period | Duration of illness | Predominant symptoms | Foods commonly implicated |
|---|---|---|---|---|
| Bacteria | ||||
| Campylobacter jejuni | 1–10 days (usually 2–5 days) | 2–5 days occasionally >10 days | Sudden onset of diarrhoea, abdominal pain, nausea, vomiting | Raw or undercooked poultry, raw milk, raw or undercooked meat, untreated water |
| E. coli enterohaemorrhagic (STEC, VTEC) | 2–10 days | 5–10 days | Severe colic, mild to profuse bloody diarrhoea can lead to haemolytic uraemic syndrome | Many raw foods (especially minced beef), unpasteurised milk, contaminated water |
| E. coli enteropathogenic enterotoxigenic enteroinvasive | 12–72 hrs (enterotoxigenic) | 3–14 days | Severe colic, watery to profuse diarrhoea, sometimes bloody | Many raw foods, food contaminated by faecal matter, contaminated water |
| Salmonella serovars (non-typhoid) | 6–72 hrs | 3–5 days | Abdominal pain, diarrhoea, chills, fever, malaise | Raw or undercooked meat and chicken, raw or undercooked eggs and egg products |
| Salmonella Typhi/ paratyphi | Typhoid 8–14 days Paratyphoid 1–10 days |
Days-weeks (chronic asymptomatic carriers can occur) | Systemic illness - sustained fever, headache and constipation rather than diarrhoea | Raw shellfish, salads, contaminated water |
| Shigella spp. | 12–96 hrs | 4–7 days | Malaise, fever, vomiting, diarrhoea (blood & mucus) | Foods contaminated by infected food handlers and untreated water contaminated by human faeces |
| Yersinia enterocolitica | 3–7 days | 1–21 days | Acute diarrhoea sometimes bloody, fever, vomiting | Raw meat especially pork, raw or undercooked poultry, milk and milk products |
| Vibrio cholerae | A few hours to 5 days | 3–4 days | Asymptomatic to profuse painless watery diarrhoea, dehydration | Raw seafood, contaminated water |
| Vibrio parahaemolyticus | 4–30 hours (usually 12–24 hrs) | 1–7 days | Abdominal pain, diarrhoea, vomiting and sometimes fever. Illness of moderate severity | Raw and lightly cooked fish, shellfish, other seafoods |
| Listeria monocytogenes | 3–70 days | Varies | Gastrointestinal symptoms rare; flu-like symptoms to meningitis/septicaemia; infection in pregnancy can result in abortions, neonatal infection | Unpasteurised milk, soft cheese, pate, coleslaw, salads, ready to eat seafood, cold meats, fresh fruit drinks |
| Viruses | ||||
| Norovirus (and other viral gastroenteritis) | 24-48 hrs | 12–60 hrs | Severe vomiting, diarrhoea | Oysters, clams, foods contaminated by infected food handlers and untreated water contaminated by human faeces |
| Rotaviruses | 24-72 hrs | Up to 7 days | Malaise, headache, fever, vomiting, diarrhoea | Foods contaminated by infected food handlers and untreated water contaminated by human faeces |
| Hepatitis A | 15-50 days | usually 1-2 weeks | Fever, nausea, abdominal discomfort, possibly jaundice | Shellfish, foods contaminated by infected food handlers and untreated water contaminated by human faeces |
| Parasites | ||||
| Cryptosporidium | 1-12 days | 4-21 days | Profuse watery diarrhoea, abdominal pain | Foods contaminated by infected food handlers and untreated water contaminated by human faeces |
| Giardia lamblia | 1-3 weeks | 1-2 weeks to months | Loose pale greasy stools, abdominal pain | Foods contaminated by infected food handlers and untreated water contaminated by human faeces |
| Entamoeba histolytica | 2-4 weeks | Weeks to months | Colic, mucous or bloody diarrhoea | Foods contaminated by infected food handlers and untreated water contaminated by human faeces |
| Toxin producing bacteria | ||||
| B. cereus (toxin in food) | 1-6 hrs (vomiting)or 6-24 hrs (diarrhoea) | < 24 hrs | Two known toxins causing nausea and vomiting or diarrhoea and cramps | Cereals, rice, meat products, soups, vegetables |
| Clostridium botulinum | 12-36 hrs | Variable | (Neurotoxin)Blurred or double vision, difficulty swallowing, respiratory paralysis, muscle weakness and lethargy | Canned food, often home canned food (low acid) |
| C. perfringens (toxin in gut) | 6 –24 hrs | 24 hrs | Sudden onset colic, diarrhoea | Meats, poultry, stews, gravies, (often inadequately reheated or held warm) |
| Staphylococcus aureus (toxin in food) | 30 min - 8 hrs | 24 hrs | Acute vomiting, and cramps, may lead to collapse | Cold foods (much handled during preparation) milk products, salted meats |
| Fish / shellfish toxins | ||||
| Scombroid fish poisoning (histamine poisoning) | Few hours | Up to 12 hours | Tingling and burning around mouth, sweating, diarrhoea, vomiting, headache, dizziness | Fish such as tuna, mackerel, skipjack, bonito, herring and sardines. Fish stored at > 5 ° C for extended periods |
| Ciguatera poisoning | Less than 24 hours | Weeks to months | Numbness and tingling around mouth, diarrhoea, vomiting and nausea followed by neurological symptoms such as dizziness, blurred vision and temperature reversal. | Large tropical reef fish |
| Paralytic shellfish poisoning (PSP) | Minutes to several hours | Several days | Burning and tingling around the mouth and extremities, nausea dizziness, potentially muscle and respiratory paralysis | Bivalve molluscs |
| Diarrhetic shellfish | 30 mins – 2 hrs | Hours to 3 days | Diarrhoea, nausea, vomiting and | Mussels, scallops and clams |
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