What is Giardia lamblia?

What is Giardia lamblia?
Giardia lamblia, also known as Giardia intestinalis or Giardia duodenalis, is a protozoan (single celled) parasite that colonises’ and reproduces in the small intestine.  It is a common parasite in many domestic animals, but can also infect humans. Infection by this parasite causes giardiasis, which is the most common cause of gastrointestinal disease and “travellers’ diarrhoea”.

What are the health effects?
Some lucky people will not have any symptoms. The unlucky ones may experience: abdominal pains; watery diarrhoea alternating with normal stools and constipation; foul smelling flatulence and belching; mild fever; malabsorption of protein, fat and other nutrients; and nausea. Symptoms can be more severe in people with impaired immune systems. Symptoms usually begin to show 7-14 days after infection and last for varying periods of time. In the UK it is most common in children under 5 years old and young adults. Although it is difficult to diagnose, treatment is available, often given on the basis of empirical evidence.

How does infection occur?
There are two forms of Giardia lamblia:

  1. The active form – the trophozoite. This attaches to the lining of the small intestine and is the cause of the signs and symptoms. It cannot live long outside of the body so this form does not typically spread the infection. However, it does produce the 2nd form, the cyst.
  2. The inactive form – the cyst. This can last for prolonged periods of time outside the body. It is fairly tough and can withstand cold conditions. Once ingested, the stomach acid activates it and it develops into the active trophozoite. It can take as few as ten cysts to cause infection.

Infections can be spread through:

  • Person to person by the ingestion of foods/water contaminated with faeces. The faecal-oral route is caused by poor hygiene and hand washing practices. This is the most common route of contamination into the drinking water supply within a workplace.
  • Recreational waters such as water parks, hot tubs and swimming pools where an infected person may have been.
  • Drinking untreated water, which contains the cyst. It can often be found in natural bodies of water such as fresh water lakes, reservoirs and streams. This is more common in less developed countries and is the main cause of ‘traveller’s diarrhoea’.

How do I know if it is present?
It takes several gallons of water to test for the presence of Giardia lamblia cysts, and even then they may not be detected. Therefore routine sampling for their presence is impractical and uneconomical. Since the presence of this protozoan is rare in the drinking water supply within a workplace, the best way to identify faecal contamination is to regularly test for the presence of Coliform species and more specifically thermotolerant E.Coli (See Assurity Consulting guides on Drinking Water Quality: Coliforms and E.Coli). If Coliform species are not present, it is unlikely that Giardia lamblia would be. Giardia lamblia is a tough cyst. It is resistant to chlorination and can survive other water treatment techniques. Water filtration is a good method of removal. However, the best method is prevention.

How do I prevent Giardia lamblia from occurring within my drinking water?
Good hygiene! Drinking water supplied directly from the mains is very unlikely to be contaminated with Giardia lamblia. Where drinking water is supplied via a water cooler/water machine it will only become contaminated with Giardia lamblia if very poor hygiene practices are allowed to occur.  The following will help prevent contamination of your water cooler/water machines:

  • Have a regular cleaning regime in place that is site specific depending on the frequency of use.
  • Ensure that staff responsible for cleaning the machines is sufficiently trained and are aware of the potential
    contamination risks that can occur whilst cleaning. This means not using the same cloths to clean the water cooler/water machine nozzles, work surfaces and taps.
  • Discourage staff from filling personal water bottles, as this can also cause contamination.

This guide is of a general nature; specific advice can be obtained from Assurity Consulting. Assurity Consulting is the UK's leading independent compliance consultancy specialising in workplace health, safety and environmental solutions. We have over 30 years' experience of helping customers of all sizes, from across all sectors, manage their compliance responsibilities, making sure that their organisation is compliant, their employees are safe, their processes are cost effective and their management team is in control.

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