Giardia

Hazard Identification What is Giardia? single-celled flagellate protozoan order Diplomonadida Giardia is a single-celled flagellate protozoan parasite belonging to the order Diplomonadida. The cells The cells are unusual in having two nuclei. species important Giardia intestinalis The species important in human illness is Giardia intestinalis (previously referred to as G. lamblia, or G. duodenalis).

G. intestinalis G. intestinalis is also found in a number of animals, including cattle, cats and dogs. an obligate parasite G. intestinalis is an obligate parasite and requires a host in order to multiply.

gastrointestinal infection It is a cause of gastrointestinal infection (giardiasis) in humans and some other animals, and is found worldwide. two-stage life cycle G. intestinalis has a two-stage life cycle, and exists in two forms. 1) Trophozoite: Pear-shaped flagellated multiplies within the gastrointestinal tract of the host. excreted in the host’s faeces but die quickly. Is not transmissible stage in the cycle 2) Cyst: Spore-like resistant cysts within the small intestine. excreted in the host’s faeces. transmissible stage in the cycle

Occurrence in Foods surface water polluted by human or animal faeces G. intestinalis is mainly associated with surface water that has been polluted by human or animal faeces unprocessed foods But cysts have also been found in a number of unprocessed foods, including:  Root crops  Lettuce  Strawberries G. intestinalis: grow  does not grow in foods or in water multiply  does not multiply in the environment outside of a suitable host

destroyed by heat Cysts are destroyed by heat and G. intestinalis is not normally associated with cooked and processed foods. contaminated water during production Any food that may come into contact with contaminated water during production, and where there is no subsequent process that will destroy cysts, may be at risk from G. intestinalis contamination. food is not a major vehicle However, food is not a major vehicle for the transmission of the parasite. waterborneperson-to-person The waterborne and person-to-person transmission routes are thought to be much more common that foodborn rout.

Hazard Characterisation Effects on Health gastrointestinal infection G. intestinalis can cause an acute gastrointestinal infection in humans. Children vulnerable Children are especially vulnerable to infection. The mechanism by which it causes disease is unclear. trophozoites attach to the epithelial cells lining the gut The trophozoites probably attach to the epithelial cells lining the gut, but do not invade the cells. They may produce a toxin in the small intestine, but this has not been confirmed. incubation time The incubation time for the infection is usually between 1–3 weeks from ingestion of cysts.

The main symptom are:  Diarrhoea  Abdominal pain.  Fever symptomslast In healthy adults, symptoms typically last for 1–2 weeks. self-limiting The infection is generally self-limiting in most cases, but drug treatment is sometimes required. immunocompromised individuals deaths However, in immunocompromised individuals, infection can be more serious and long lasting, requiring hospital treatment, and occasional deaths have been recorded. infective dose very low 10 cysts The infective dose is thought to be very low and ingestion of as few as 10 cysts.

Incidence and Outbreaks most commonly developed world G. intestinalis is probably the most commonly reported intestinal parasite in the developed world. European countries with the highest reported incidence: The European countries with the highest reported incidence:  Estonia (24.28 cases per people)  Iceland (14.65 cases per people) hildren aged 0–4 years were most commonly infected. The results also show that children aged 0–4 years were most commonly infected. peaks of infection There are seasonal peaks of infection in spring and autumn. There were reported cases of giardiasis in the USA in 2005.

Sources obligate parasite originates from the host. G. intestinalis is an obligate parasite and thus originates from the host. The primary source The primary source of G. intestinalis is the faeces of infected humans and animals, which may contain up to 10 9 cysts in a single day. The cysts are extremely infectious and may be transferred to food via an infected food handler, or through polluted water used for crop irrigation or processing. cysts are larger relatively easy to remove G. intestinalis cysts are larger than those of Cryptosporidium (9–12 µm diameter) and are relatively easy to remove from water using modern water treatment methods. less resistant to chlorineare not inactivated by the concentrations normally They are also less resistant to chlorine, but are not inactivated by the concentrations normally used to treat water.

They are much less likely to pass through water- treatment plants into the public water supply system.

Stability in Foods are generally resistant to environmental factors. G. intestinalis cysts are generally resistant to environmental factors. persist for months Cysts can persist for months in cool and moist conditions. However, there is little information on their survival and inactivation in foods. relatively resistant to some sanitisers and disinfectants The cysts are relatively resistant to some sanitisers and disinfectants, notably chlorine and ozone. destroyed milk pasteurisation G. intestinalis cysts are not heat resistant and are destroyed by conventional milk pasteurisation. 60–70 0 C for 10 min A temperature of 60–70 0 C for 10 min is reported to inactivate cysts completely.

cooking processes Therefore, most controlled cooking processes used in food production should destroy any viable cysts in the product. survive below 0 0 C Oocysts can survive for significant periods at temperatures below 0 0 C, especially in water frozen inactivation But frozen storage is reported to cause inactivation.

Control Options Control measures focus Control measures for G. intestinalis in food processing focus largely on the control of contamination in water and the management of infected food handlers. Processing Care should be taken to ensure that raw-food ingredients and products that do not undergo further processing do not come into contact with contaminated surface water. Fresh produce should be obtained from suppliers practicing good agricultural practice. using potable quality water Fresh produce and other raw foods should only be washed/processed using potable quality water.

Heat processing is an effective Heat processing is an effective control against G. intestinalis cysts in food. Normal milk-pasteurisation processes are effective Normal milk-pasteurisation processes are effective, as are recommended ‘‘Listeria cook’’ processes for meat products (70 0 C for at least 2 min). Reheating cooked foods 74 0 C Reheating cooked foods to at least 74 0 C will destroy cysts immediately. Freezing7 days Freezing foods for at least 7 days is also an effective control.

Hygiene food handlers Infected food handlers are also a major G. intestinalis contamination risk for foods that do not undergo any further processing, such as sandwiches and salads. hand washing Good personal hygiene practice, especially hand washing, is an essential control. Any staff suffering from gastroenteritis should be excluded from processing areas.

Legislation It is not usually mentioned specifically in food safety and hygiene law.