Bali belly or a parasite? Giardia, timing, and the stool test

Which parasites are we talking about?

The Better Health Channel names three among the causes of traveller's diarrhoea: Giardia intestinalis, Entamoeba histolytica and Cryptosporidium parvum. Giardia is the one most travellers to Southeast Asia encounter, and the one with the clearest published picture, so it is the one this page leans on.

healthdirect describes giardiasis as an infection of the small intestine caused by a parasite called giardia, also written as Giardia duodenalis, Giardia lamblia or Giardia intestinalis, which are three names for the same organism and a common source of confusion when you start reading.

It gets around the way everything else here does. The parasite lives in the faeces of infected people or animals, and you pick it up by eating contaminated food or by putting hands or objects in your mouth after they have touched infected faeces. Contaminated water is a classic route, which is why the Bali water page is blunt about ice and toothbrushes.

The timing tell

This is the single most useful distinction on the page, and it is why people miss it. Bacteria move fast. Giardia does not.

Symptoms of giardiasis start 3 to 25 days after infection with the parasite.

Three to twenty five days. A fortnight after the warung you suspect, you have stopped connecting the two, and if you flew home in between you are probably blaming something you ate in Australia. The travel history is the piece of information your GP needs and the piece you are most likely to leave out.

The other end of the timeline is just as distinctive:

They may last for months, especially if left untreated.

Months. Nothing bacterial behaves like that. If you are into week three of an unsettled gut, this is the conversation to have.

What it feels like, and how it differs

healthdirect's symptom list for giardiasis is diarrhoea, stomach cramps and bloating, excessive gas, nausea, fatigue and weight loss. Read next to an ordinary bout of Bali belly, three things stand out.

The stool test, and what to ask for

Diagnosis is not clinical guesswork, it is a lab result. healthdirect's description is straightforward: your doctor may send a sample of your stool to the lab to be tested for giardia.

Three practical things worth knowing before you go in. Say where you have been and when, because a travel history changes which tests get ordered. Expect to provide more than one sample in some cases, since the parasite is shed intermittently and a single negative does not always settle it. And do not start any antibiotic left over from a previous trip, because taking something before the sample can muddy the result and is poor practice regardless.

healthdirect also notes that many people with giardiasis get better without treatment, so a positive result is not automatically a prescription. That is a decision for the doctor with the result in front of them, not for a website that sells probiotics.

What happens if it is positive

Treatment where it is needed is a prescription anti-parasitic or antibiotic medicine, and hydration alongside it. It is not something to source over the counter in Bali on a hunch, and it is not something we will describe in any more detail than that, because dose and choice are a prescriber's job.

There is an exclusion rule attached, and it is worth respecting because giardia spreads easily within a household. healthdirect's advice is to keep infected people away from childcare, pre-school, school or work until they have had no diarrhoea for at least 24 hours. If someone in your house has it, the hand washing rules on the contagious page apply at home too.

Not picking one up in the first place

The habits are the same as for everything else in this family, because the route is the same. Sealed or properly filtered water for drinking and for your toothbrush, ice only from places with real turnover, fruit you peel, hot food served hot, and hands washed with soap before you eat.

Two extras that matter specifically for parasites. Swimming water counts: Cryptosporidium in particular tolerates chlorine better than most organisms, so a poorly maintained pool is a genuine route. And animal contact counts, because giardia lives in animal faeces as well as human. Bali has a great many dogs, cats and monkeys with no interest in your hand hygiene.

How to avoid Bali belly has the food and water habits in full.