Considering Chronic Giardiasis as a Differential in Presentations of Chronic Gastrointestinal Symptoms in Primary Care

Considering Chronic Giardiasis as a Differential in Presentations of Chronic Gastrointestinal Symptoms in Primary Care

Dr Mohammed Faiz uddin Anwar.1, Dr Khalil Ahmad.2

1- Dr Mohammed Faiz uddin Anwar MRCGP (UK), MBBS (Lon), BSc (MedEd)

2- Dr Khalil Ahmad MRCGP (UK), MRCS (Ed), MBBS.

*Correspondence to:


© 2024 Dr. M F Anwar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: 22 January 2024

Published: 01 February 2024


A 38-year-old male, who had moved to the UK from India 12 months earlier, presented to his primary care health centre with a history of chronic intermittent loose stools and occasional abdominal discomfort. He suffered with bloating, flatulence, reflux and occasional nausea.  He complained of tiredness and fatigue but did not report weight loss. Prior to this he had been seen for stress and anxiousness.

Examination was unremarkable and his BMI was 27. H pylori stool test was negative. Faecal calprotectin was normal. His bloods showed a Vitamin B12 96, Vit D 17, with normal CBC, LFTs, U&Es and a normal CRP and ESR.

Symptoms were attributed to dyspepsia and likely irritable bowel syndrome. He was managed symptomatically with Esomeprazole, Antacid, Mebeverine and as required loperamide.

He was followed up 2 months later and reported some symptomatic relief with the treatment but complained of persisting intermittent chronic loose stools. The attending physician ordered stool cultures which were positive for Giardia cysts. He was treated with metronidazole and subsequently reported symptoms to have significantly improved.

Considering Chronic Giardiasis as a Differential in Presentations of Chronic Gastrointestinal Symptoms in Primary Care


Giardiasis, caused by the protozoan parasite Giardia lamblia (syn. intestinalis, duodenalis), is considered the commonest opportunistic parasitic infection of the human intestine both in developed and developing countries.(1–5) It can be asymptomatic or, manifest as acute or chronic symptoms.(6) It is easily treatable(7) but chronic giardiasis can be missed as a diagnosis due to its non-specific symptoms resembling other gastrointestinal ailments.(8,9) Thus, making it essential to recognise the different presentations of giardiasis, its transmission and sequalae.



Its prevalence can vary from 2% in developed countries to 30% in developing countries.(10) It can also be influenced by socioeconomic status, age and gender.(1,11,12)  In the UK there are approximately 4000 laboratory confirmed cases each year with the highest incidence in children aged under 5 years and adults aged 25-44.(1,13) In the US, an estimated 1.2 million cases occur annually but less than 20,000 are reported.(14) In India, the prevalence varies significantly and can be as high as 70% in cases of diarrhoea and asymptomatic cyst passage being as high as 50% in some populations.(15)


Life cycle and transmission

Giardia has a two-stage life cycle and preferably colonizes the proximal small intestine. Cysts, which are generally metabolically inactive and acid resistant, are considered immediately infectious upon excretion in the faeces. When ingested by the host, via contaminated water or food, they pass through the stomach into the small intestine where excystation causes the release of trophozoites. Trophozoites that do not attach to the duodenal or jejunal mucosal surfaces, move onwards to the large intestine where they revert to the infectious cyst form. They are passed back to the environment as infectious cysts excreted in faeces and, in cases of diarrhoea, can also be found as trophozoites in stool.(2,7,16,17)


Clinical manifestations

These can vary from asymptomatic to acute or chronic. It may be asymptomatic in adults and children which cyst shedding lasting 6 months or more. It may impair growth in asymptomatic children without any associated diarrhoea.(17)

In acute manifestations the symptoms present with diarrhoea, malaise, steatorrhea, flatulence, abdominal cramps, nausea and weight loss in majority cases. Vomiting, fever or urticaria may be present in some cases. Symptoms usually develop after an incubation period of 7-14 days and can last between 1-4 weeks.(1,6,17,18)

Chronic giardiasis may develop with or without an acute phase. This can include loose stools (diarrhoea is less likely), malaise, fatigue, flatulence, burping, steatorrhea, malabsorption and borborygmi. These symptoms may be intermittent and over many months.(6,17,19–22) Persistent giardiasis causes duodenal inflammation, affecting epithelial transport and barrier functions, thus contributing to malabsorption. This in turn affects growth and cognitive development in children.(21,23,24)


Chronic giardiasis and irritable bowel syndrome

Chronic giardiasis can present as chronic loose stools, abdominal discomfort and gastrointestinal complaints resembling symptoms of irritable bowel syndrome (IBS). The course of chronic giardiasis and its association with chronic or intermittent loose stools highlights the importance of considering it as a differential diagnosis in presentations of chronic gastrointestinal symptoms. Additionally, IBS, chronic fatigue are associated long-term sequalae of chronic giardiasis amongst others.(21,25,26) These potential consequences of giardiasis are more serious than previously known.



In conclusion, testing for this parasitic infection should be actively considered by primary care physicians in presentations of chronic gastrointestinal symptoms. It is underreported and underdiagnosed with no pertinent travel history.(27) It was included in the WHO neglected diseases initiative and deserves a comprehensive approach.(28) Accurate diagnosis will help to mitigate the impact on the patients’ health, wellbeing and has obvious public health benefits.



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