Gastrointestinal Parasitic Infections Flashcards
GI Infection - Example Question
A 35-year-old female who has recently emigrated from Pakistan presents is investigated for abdominal pain and diarrhoea.
Around 4 months ago she was investigated in Pakistan for an episode of dyspnoea, wheezing, fever and malaise. No cause was found at the time and she improved after 3 weeks.
A barium enema is performed:
SEE PASSMED BARIUM ENEMA ASCARIASIS
What is the most likely diagnosis?
> Ascariasis Enterobiasis Giardiasis Carcinoid syndrome Ulcerative colitis
This patient has Ascariasis. The episode in Pakistan is likely to be Loffler’s syndrome whilst the parasite was migrating through lungs.
Enterobiasis
Due to organism Enterobius vermicularis
Common cause of pruritus ani
Diagnosis usually made by placing scotch tape at the anus, this will trap eggs that can then be viewed microscopically
Treatment is with mebendazole
Ancylostoma Duodenale
Hookworms that anchor in proximal small bowel
Most infections are asymptomatic although may cause iron deficiency anaemia
Larvae may be found in stools left at ambient temperature, otherwise infection is difficult to diagnose
Infection occurs as a result of cutaneous penetration, migrates to lungs, coughed up and then swallowed
Treatment is with mebendazole
Ascariasis
Due to infection with roundworm Ascaris lumbricoides
Infections begin in gut following ingestion, then penetrate duodenal wall to migrate to lungs, coughed up and swallowed, cycle begins again
Diagnosis is made by identification of worm or eggs within faeces
Treatment is with mebendazole
Strongyloides
Due to infection with Strongyloides stercoralis
Rare in west
Organism is a nematode living in duodenum of host
Initial infection is via skin penetration. They then migrate to lungs and are coughed up and swallowed. Then mature in small bowel are excreted and cycle begins again
An auto infective cycle is also recognised where larvae will penetrate colonic wall
Individuals may be asymptomatic, although they may also have respiratory disease and skin lesions
Diagnosis is usually made by stool microscopy
In the UK mebendazole is used for treatment
Cryptosporidium
Protozoal infection
Organisms produce cysts which are excreted and thereby cause new infections
Symptoms consist of diarrhoea and cramping abdominal pains. Symptoms are worse in immunosuppressed people
Cysts may be identified in stools
Treatment is with metronidazole
Giardiasis
Diarrhoeal infection caused by Giardia lamblia (protozoan)
Infections occur as a result of ingestion of cysts
Symptoms are usually gastrointestinal with abdominal pain, bloating and passage of soft or loose stools
Diagnosis is by serology or stool microscopy
First line treatment is with metronidazole
Giardiasis - Example Question
A 26-year-old woman presents to the Emergency department some 2 weeks after returning from her honeymoon in the Seychelles. Since returning she has suffered from intermittent abdominal bloating and diarrhoea and feels she has lost a little weight. Physical examination reveals a blood pressure of 118/82 mmHg, and her pulse is 70 and regular. There is mild abdominal distension and her body mass index is 22 kg/m²
Investigations:
Hb 110 g/l Na+ 138 mmol/l Platelets 210 * 109/l K+ 4.0 mmol/l WBC 11.2 * 109/l Urea 6.9 mmol/l Neuts 8.1 * 109/l Creatinine 89 µmol/l Lymphs 1.5 * 109/l CRP 82 mg/l Albumin 34 g/l
Which of the following is the most appropriate intervention?
Amoxicillin Ciprofloxacin Gluten free diet Lactose free diet > Metronidazole
The most likely diagnosis, given the trip to a tropical region of Africa, intermittent bloating and diarrhoea, and an elevated CRP, is Giardiasis. Empirical treatment is often given, with either a course of metronidazole or a single dose of 2g tinidazole. Food intolerances may persist, particularly with respect to lactose, for some time after the initial infection.
Amoxicillin and ciprofloxacin would usually be used for listeriosis and campylobacter respectively, and neither infection is likely. Neither a wheat free diet nor a lactose-free diet is indicated given the likelihood of ongoing giardiasis, although many patients may suffer symptoms of lactose intolerance post-giardiasis.
Giardiasis
Giardiasis
Giardiasis is caused by the flagellate protozoan Giardia lamblia. It is spread by the faeco-oral route
Features
often asymptomatic
lethargy, bloating, abdominal pain
non-bloody diarrhoea
chronic diarrhoea, malabsorption and lactose intolerance can occur
stool microscopy for trophozoite and cysts are classically negative, therefore duodenal fluid aspirates or ‘string tests’ (fluid absorbed onto swallowed string) are sometimes needed
Treatment is with metronidazole
