Food or water-borne illness

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Food or water-borne illness

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

Infectious diseasesepidemiology and surveillance

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