Giardia and Intestinal Parasites After Travel in Sri Lanka: When Diarrhea Won't Go Away

Most of the stomach trouble we see in Arugam Bay is over within a few days — a rough forty-eight hours, some ORS, then back to the beach. But every month or so, someone walks in who’s had loose stools for a week, ten days, sometimes longer, and they’re starting to worry something is seriously wrong. Often the answer is a parasite, most commonly Giardia, and once you know what to look for, it’s straightforward to diagnose and treat.

What Giardia actually is

Giardia lamblia is a microscopic parasite that lives in the small intestine. It spreads through water or food contaminated with cysts from infected stool — unfiltered well water, ice made from untreated water, salads washed in tap water, or occasionally contact with an infected person who hasn’t washed their hands properly. It’s common wherever sanitation is inconsistent, and Sri Lanka’s guesthouse and street-food scene, wonderful as it is, gives it plenty of opportunities.

Other intestinal parasites — Cryptosporidium, amoebas, various worms — can cause a similar picture, but Giardia is by far the one we see most in travelers here.

Why it feels different from ordinary food poisoning

Regular traveler’s diarrhea (the kind covered in our food poisoning guide) tends to hit hard and fast — cramping, watery stools, maybe fever, and then it’s done within three to five days. Giardia behaves differently:

• It comes on gradually, often five to twelve days after exposure, rather than suddenly
• Diarrhea is often pale, greasy, and foul-smelling, rather than simply watery
• Bloating and excess gas are prominent — often the most annoying symptom, worse than the diarrhea itself
• Cramping is more of a dull ache than sharp pain
• Fever is usually mild or absent, unlike bacterial infections
• Appetite drops and weight loss creeps in if it drags on for more than a week or two
• It can come and go. A few better days followed by a relapse is a classic pattern, and it catches people out — they think they’re recovering and then it’s back.

The biggest clue is simply duration: if a stomach bug in Sri Lanka hasn’t settled after five to seven days of reasonable fluid and rest, parasites move up the list of likely causes.

What we do at the clinic

Giardia is usually diagnosed from a stool sample, though it can take a couple of samples over different days to catch it, since the parasite doesn’t shed constantly. We run this in-house and usually have a result the same day. If your symptoms and history (untreated water, a questionable salad, a long stay) make Giardia likely, we’ll sometimes start treatment based on clinical judgment without waiting on results, especially if you’re due to travel on soon.

Treatment is a short course of an antiparasitic — usually metronidazole or tinidazole — taken for a few days. Most people notice improvement within forty-eight hours of starting, though bloating and loose stools can linger for a week or two after the parasite itself is gone while your gut lining recovers. We’ll also check you’re not dehydrated and advise on diet during that recovery window.

One practical note: alcohol and metronidazole don’t mix — it causes a genuinely unpleasant reaction (flushing, nausea, a racing heart). If we put you on it, that’s a few dry days in a surf town, which is annoying but temporary.

When to come in rather than wait it out

See us if:

• Diarrhea has lasted more than five to seven days
• You have bloating, excess gas, or greasy-smelling stools alongside the diarrhea
• Symptoms improve and then relapse
• You’re losing weight or your appetite has dropped significantly
• There’s blood in the stool, a high fever, or severe abdominal pain (these point toward something else and need prompt assessment)
• You’re due to fly home soon and want a clear answer rather than guessing

Don’t just push through on loperamide for two weeks hoping it resolves on its own. It’s a quick stool test and a short, well-tolerated course of medication, not a complicated problem, but it doesn’t fix itself the way a routine bacterial bug usually does.

Reducing your risk

• Stick to bottled or properly filtered water, including for brushing your teeth if you’re being careful
• Avoid ice unless you know it’s made from purified water
• Be selective with raw salads and unpeeled fruit, particularly from informal stalls
• Wash your hands before eating, especially after using a shared bathroom in a guesthouse
• Avoid swallowing water when swimming in rivers, lagoons, or wells used for bathing

None of this means being paranoid about Sri Lankan food — it’s one of the best reasons to come here. It just means that if a stomach bug outstays its welcome, there’s a specific, treatable reason, and no need to tough it out for the rest of your trip.

Related reading

• Food Poisoning and Traveler’s Diarrhea in Sri Lanka
• Dehydration, ORS, and IV Drips: When Fluids Alone Aren’t Enough
• Food and Water Safety in Sri Lanka

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This article is general health information and not a substitute for medical advice. If diarrhea has lasted more than five days, walk in to see us any time, 24/7, or call 1990 for free emergency transport if you’re too unwell to travel yourself.