Giardia Infection (Giardiasis): Symptoms, Prevention and UK Travel Advice

Giardiasis is an infection of the small intestine caused by a microscopic parasite called Giardia intestinalis (also known as Giardia lamblia). It is one of the most common causes of waterborne disease worldwide. Unlike many bacterial causes of travellers' diarrhoea, Giardia is a protozoan, meaning it is a single-celled organism that can survive in the environment for long periods, particularly in cold water, due to its protective outer shell known as a cyst.

In the UK, while cases do occur domestically through contaminated swimming pools or person-to-person contact, it is most frequently diagnosed in travellers returning from regions with poor sanitation. According to NHS guidance, the infection is spread via the faecal-oral route. This occurs when a person swallows the Giardia cysts, often by consuming contaminated water, food, or by touching surfaces and then their mouth.

The symptoms of a Giardia infection typically appear between one to three weeks after exposure. One of the most characteristic signs of Giardiasis that differentiates it from other stomach bugs is the nature of the stools. Patients often report steatorrhoea—pale, greasy, and foul-smelling stools that may float. Other common symptoms include:

• Stomach cramps and pain: Often sharp and localized in the upper abdomen.
• Bloating and flatulence: Many patients experience excessive wind that is notably sulphuric or 'eggy' in smell.
• Nausea: A general feeling of sickness, sometimes accompanied by vomiting.
• Dehydration: Resulting from persistent diarrhoea.
• Weight loss: If the infection becomes chronic, it can lead to malabsorption, where the body fails to take in nutrients properly.

It is important to note that some individuals carry the parasite without showing any symptoms at all, yet they can still spread the infection to others.

Giardia is found globally, but the risk is significantly higher in areas where water treatment systems are less robust. Sub-Saharan Africa, parts of Southeast Asia, and Central and South America are high-risk zones. However, outbreaks have also been noted in popular trekking destinations in Eastern Europe and even in North American wilderness areas.

How is it transmitted?

• Water: Drinking untreated water from lakes, rivers, or shallow wells. Even 'clear' mountain water can be contaminated by animal faeces.
• Food: Eating raw fruits or vegetables washed in contaminated water.
• Surfaces: Touching taps, door handles, or changing nappies and then failing to wash hands thoroughly.
• Recreational water: Accidnetally swallowing water in swimming pools or water parks that have not been adequately chlorinated.

Following NICE (National Institute for Health and Care Excellence) principles for travel health, prevention is the primary line of defence. When travelling to areas where Giardia is prevalent, you should adhere to the 'boil it, cook it, peel it, or forget it' rule.

Always drink bottled water with an intact seal or use water that has been boiled for at least one minute. Chemical treatments like chlorine or iodine are less effective against Giardia cysts than they are against bacteria; therefore, using a high-quality portable water filter with a pore size of 1 micron or less is recommended for hikers and backpackers. Avoid ice in drinks, as freezing does not kill the parasite, and ensure you use bottled water for brushing your teeth. Frequent handwashing with soap and water is essential, as alcohol-based hand gels are not always effective against all types of parasites.

If you suspect you have Giardia, a GP will usually request a stool sample. Because the parasite is shed intermittently, you may be asked to provide samples from three different days to increase the accuracy of the test. In some cases, a more advanced test called an ELISA (enzyme-linked immunosorbent assay) is used to detect Giardia antigens.

Once confirmed, treatment is usually straightforward. The most common treatment in the UK is a short course of antibiotics, typically Metronidazole or Tinidazole. It is vital to complete the full course even if you feel better after the first dose. During recovery, it is common to experience temporary lactose intolerance, as the parasite can damage the lining of the gut. Avoiding dairy products for a few weeks after treatment can help settle the stomach.

When you are back in the UK and dealing with persistent digestive issues, you may find it difficult to secure a same-day appointment with your local surgery. You can speak to a GP online to discuss your travel history and symptoms. An online doctor can provide a professional assessment, advise on the necessary diagnostic tests, and issue private prescriptions for treatment if appropriate.

Consulting an online doctor is particularly useful if your symptoms are not resolving after a week or if you are worried about recurring bloating and diarrhoea following a trip abroad. They can also provide a sick note if your symptoms are preventing you from returning to work. Early intervention is key to preventing the infection from becoming chronic and causing long-term nutritional deficiencies.