The giardia parasite or to be moreprecise – ‘giardia intestinalis’ - are types of organisms whichcause an infection very similar to other forms of food poisoning.
Although the main difference here isthat this is caused by drinking infected or untreated water rather thancontaminated food. However, salads and vegetables which have been washedin infected water will also cause this illness.
The medical term for this disease is‘giardiasis’.
This illness can occur in any partof the world which includes the UK but it is more commonly seen in developingcountries. This is due to the fact that they have limited supplies ofclean water and poor sanitation facilities.
Giardiasis is a particular problemfor young children in those countries who are at greater risk of dehydrationdue to diarrhoea and other symptoms. Prolonged bouts of diarrhoea canlead to dehydration which can be fatal in babies and infants.
This illness is similar to cryptosporidium.
The giardia intestinalis parasite
This is a unicellular parasite whichlives within the small intestine of people and animals. It does notinvade cells within the lining of the intestinal walls or spread intothe bloodstream as happens with other types of food poisoning; ratherit remains attached to the intestinal wall.
Once there it reproduces asexually.
Causes of giardiasis
This occurs from any of the following:
- Drinking water which isuntreated or contaminated by infected faeces.
- Eating foods such as fruitor vegetables which have been washed in contaminated water.
- Failure to wash the handsproperly after visiting the toilet followed by contact with food.
- Anal sex
Parents and anyone who works in childcare,and who are required to change nappies are also at risk of this illness.If they change the nappy of a baby who has developed giardiasis thenthey too are at risk. They may come into contact with faeces which havebeen contaminated and then, unknowingly transmit this infection by touchingother objects, food etc.
How is the giardia parasite transmitted?
This parasite lives within the smallintestine. When faeces are expelled from the body this parasite is expelledalong with them and is able to survive outside the body for a considerableperiod of time.
These parasites form hard protectiveshells and are known as ‘giardia cysts’.
They can survive for months in coldwater which is why they often occur in mountain streams, ponds, riversand lakes. This is a particular risk for campers and people who enjoyoutdoor activities such as hiking or who swim in rivers and lakes wherethese bacteria can be found.
They are found in untreated water buteven safe sources such as reservoirs can be risky as the giardia parasitecan resist water treatment methods such as chlorination.
So, giardiasis is likely to occur inanyone who has come into contact with infected water, e.g. swimmingin a lake, or has drunk any water which has been contaminated by infectedfaeces.
This is one of the reasons why peopleare advised to boil water when travelling or consume bottled water ifnecessary.
Symptoms of giardiasis
The incubation period for this illnessis between 9 to 14 days or so after initial exposure.
Note: when we say ‘incubationperiod’ we refer to the period of time between first contact withthe parasite and the appearance of the symptoms.
The symptoms include:
- Fever
- Loss of appetite
- Nausea
- Upset stomach
- Watery diarrhoea
This diarrhoea is the main symptomof this illness and tends to be frequent and often foul smelling.
Other possible symptoms include belching(burping), bloated stomach and indigestion.
These symptoms usually ease after acouple of weeks but the diarrhoea can persist for much longer. In chroniccases, people suffer repeated bouts of diarrhoea for several years althoughthis is rare.
Interestingly enough, the majorityof people who become infected by the giardia parasite do not experienceany symptoms at all. This is known as ‘asymptomatic giardiasis’.
However, these people can still transmitthe infection to others.
Diagnosing giardiasis
This is done via a stool sample.
A stool sample is a test in which asmall sample of faeces is analysed under a microscope to check for signsof the giardia parasite. Several samples may be required.
This test is often performed in othertypes of food poisoning.
Treatment for giardiasis
Giardiasis is treated with medicationcalled metronidazole. This is available as a tablet and is a week longcourse of treatment.
Metronidazole works by killing theparasites which are responsible for giardiasis.
Side effects are rare but if you experienceanything untoward such as nausea, skin rashes, blurred vision, dizzinessor fits then consult your GP.
Complications of giardiasis
The main problem is that of dehydration.Giardiasis causes repeated bouts of diarrhoea which result in largeamounts of fluids being lost. These fluids contain essential vitaminsand minerals such as sodium which are vital for the functioning of thebody.
This is especially dangerous for childrenas they are less able to tolerate this loss of fluids as compared toan adult. They have smaller bodies than adults which contain smalleramounts of fluids so any loss has a greater effect.
It is important to drink plenty offluids such as water to prevent this from happening and to add an oralre-hydration powder. These powders are available from a pharmacy andcontain replacement vitamins and minerals.
You just add this to a glass of water.
If your child has signs of dehydrationthen try this before seeking medical advice. But if their symptoms aresevere then consult your GP.
Preventing giardiasis
Giardiasis can be prevented by adoptinga few common sense measures which include good hygiene and food safety.
They include:
- Avoid drinking untreatedwater. Buy bottled water when travelling. Boil your water if you arecamping or camping.
- Do not eat unwashed fruitand vegetables and especially if you are travelling abroad. Wash themfirst before consumption.
- Wash your hands after youvisit the toilet
- Wash your hands before youprepare or cook food
These and other precautions are discussedfurther in our preventingfood poisoning section.
If you or your child develops giardiasisthen stay away from work/school for at least 48 hours or until the symptomshave eased. Use a separate set of towels, bedding, utensils from therest of your family and always wash your hands each time you handlefood.
