Mr Davidson was a 57-year-old man who was a little overweight but generally in good health, and not taking any regular medication. When he came to see me recently he lacked his usual sparkle and said ominously that he thought there was something seriously wrong.
He had come to the surgery because of a three-week history of diarrhoea. He described the change in bowel habit as watery and more frequent. There was no blood or mucus in his stools but he was passing a lot of wind, had abdominal pains and generally felt off and unwell.
Apart from that, his history was unremarkable. Physical examination, including abdominal and rectal examination, was also unremarkable except for some diffuse abdominal tenderness.
He denied any foreign travel within the previous two years, or contact with anyone who had a GI problem. He seemed anxious and on further questioning, revealed his best friend had recently died from bowel cancer.
Basic haematological and biochemical blood tests were requested as well as three faecal cultures, the latter to be submitted at different times.
I was also anxious that this could be an early presenting feature of a colorectal malignancy and decided to keep a look out for out for his results. I arranged to see him the following week.
A few days later the result from the stool sample came back, revealing that Giardia lamblia cysts were isolated. The patient was recalled and treated with a course of metronidazole. The patient tolerated the treatment with no problems. I warned him to stay clear of alcohol because of the potential for interaction with metronidazole. Relapses can occur after treatment but this did not occur in Mr Davidson.
He returned two weeks later to say thank you as he was feeling better and had no symptoms at all.
Giardiasis is an infection of the GI tract caused by the protozoan parasite G lamblia, also called G intestinalis. Immunosuppressed patients and children are at particular risk, but it can affect patients of any age. It is more common in developing countries.
Infection is the result of consumption of G lamblia cysts. These settle in the small intestine and attach to the intestinal wall. They generate an inflammatory response that can lead to clinical symptoms.
Transmission can occur through eating contaminated food although the more common route is through drinking contaminated water. It can also be passed on through the faecal-oral route.
In 2006, nearly 3,000 cases of G lamblia infection were identified in England and Wales. Outbreaks can occur in institutions such as nurseries and nursing homes, and foreign travellers are at particular risk. It can be sexually acquired.
Many people who develop symptoms will do so a week or so after exposure to the pathogen. Diarrhoea is often a prominent symptom with an unpleasant smell from the stools. The stools are often loose and watery. Abdominal bloating with cramping pain can accompany nausea and the affected person can feel generally unwell. There is no blood or pus in the stools.
Some people can be asymptomatic but others can present with significant weight loss associated with malabsorption. Symptoms can last a few days or for weeks. They may resolve untreated. Occasionally giardiasis can lead to failure to thrive in children.
When stool samples are sent to the lab, tests for ova, cysts and parasites should be requested. The lab should also look for other pathogenic organisms that could be the cause.
The micro-organism can be hard to detect because the amount of diagnostic material in the stools can vary. Submitting three stool samples at different times increases the chances of detection. An FBC will not show either a raised white count or eosinophilia.
Not everyone infected with the parasite develops symptoms. Asymptomatic carriers are at risk of transmitting the infection. The best management of people who are asymptomatic carriers of the organism is not clear. It is possible that treatment reduces infectivity and the chances that they will develop symptoms. However, the evidence base is not firm.
It may be sensible to screen for G lamblia infection in other people living with an infected person, because it can be spread within households.
The infection is considered food poisoning and giardiasis is a notifiable disease.
The favoured treatment for G lamblia infection is metronidazole. Tinidazole and mepacrine are alternatives. In adults, metronidazole can be given as 400mg three times a day for five days, 2g daily for three days or 500mg twice a day for seven to ten days.
- Giardiasis should be considered in cases of GI illness.
- It can cause prolonged diarrhoea.
- It is not always easy to find. Three faecal samples at different times should be sent for analysis.
- It can cause failure to thrive in children.