What is giardiasis, and how does one get it?

This article sheds light on a medical condition known as giardiasis, an illness which animals spread to humans. On hand to tell us more about the disease, including the symptoms, diagnosis, and treatment, is revered London-based consultant gastroenterologist, Dr Aathavan Loganayagam. 

What is giardiasis?

Giardiasis is a zoonotic disease (one passed from animals to humans) caused by a flagellate protozoan, Giardia lamblia. Encased in a hard, shell-like cyst, the organism is found in the digestive tract of humans and many animals (domestic and wild).

How does one get giardiasis?

People can only become infected with giardia by swallowing the parasite, but it takes as few as 10 cysts to cause infection. Anything that comes into contact with faeces from infected humans or animals can become contaminated with giardia, but it is usually spread by: 

• touching contaminated surfaces such as bathroom taps or door handles
• drinking water containing the parasite
• accidentally swallowing infected water while swimming
• eating uncooked food that contains the parasite
• contact with someone who has giardiasis

Once inside their host, the microscopic cysts rapidly multiply. An infected person can shed millions of cysts a day in their faeces.

Where exactly is giardia found in the world?

Giardia occurs worldwide, particularly during the summer months. People are particularly prone to infection when travelling in countries where the parasite is common in its human and animal populations.

The highest incidence is in South and Central Asian countries, where it’s estimated that one in three people have or have had giardia. It is also quite common in the Middle East and South America. However, giardiasis also occurs in developed countries. In fact, it’s the most common internal parasitic disease affecting humans worldwide.

What are the main symptoms?

Symptoms of giardiasis normally appear after between one to two weeks after infection, but can occur as quickly as two days. In otherwise healthy people, symptoms of giardiasis may last from between two to four weeks. For those with few or no symptoms, giardia infection can clear up completely without treatment in a fortnight.

However, giardia can result in diarrhoea (often with foul-smelling, greasy stools), abdominal cramps, bloating, flatulence, fatigue, and nausea. Typically, there is a gradual onset of two to five loose stools per day and increasing fatigue.

Sometimes, upper gastrointestinal symptoms are more prominent, and weight loss may also occur over time. Fever and vomiting, however, are quite uncommon. Some sufferers, particularly infants and pregnant women, are at higher risk of dehydration.

How is giardiasis diagnosed?

For severe symptoms or persisting diarrhoea, a stool sample is needed to be collected and sent to the laboratory for testing. Until recently, up to three stool samples were required. Since most cases of giardia are found in the first sample, only one sample is needed nowadays.

How is the illness treated?

Medication containing tinidazole, metronidazole, nitazoxanide, paromomycin, furazolidone, or quinacrine, can reduce the symptoms of giardiasis and speed up recovery.

How can one prevent getting giardiasis?

Following the safe food and water guidelines is the best way to prevent giardia. If you are uncertain if water you intend to drink is safe, first boil it for one minute and allow it to cool before drinking. Chemical disinfectants or filters are also effective.

One of the most important and effective ways to avoid illness is regular hand washing, especially before handling food.

Dr Aathavan Loganayagam is a highly qualified and skilled consultant gastroenterologist who specialises in giardiasis amongst many other gastrointestinal-related medical conditions. Schedule an appointment with him today via his Top Doctors profile.