Tropical sprue: malabsorption after living in or visiting the tropics

Tropical sprue is a malabsorptive disease of the small bowel. Patient.info describes inflammation and flattening of the villi, the finger-like projections that absorb nutrients, in the small intestine. The appearance is similar to coeliac disease, but tropical sprue is not an autoimmune condition and is considered most likely to be infective.

The exact cause remains unclear. Patient.info says it is probably bacterial and may involve enterotoxic coliform bacteria, viruses or a combination of pathogens. The MSD Manual similarly says it is thought to result from chronic infection of the small bowel by toxigenic strains of coliform bacteria.

It is distinct from tropical enteropathy, which Patient.info describes as an asymptomatic condition with mild changes in the intestinal lining that co-exists in endemic areas.

Patient.info says tropical sprue usually occurs in residents of tropical or subtropical climates and, less commonly, visitors, most often in developing countries. It occurs mostly in Southeast Asia and the Caribbean and remains the most common cause of malabsorption in India. The MSD Manual lists the Caribbean, southern India and Southeast Asia, and says the illness is rare in visitors spending less than one month in endemic areas.

The condition can appear after people have left the area, with a lag of up to 10 years according to Patient.info. This is why a doctor will ask about previous residence or travel, even if it was years ago. The MSD Manual notes that the worldwide incidence has been decreasing in recent decades, perhaps because of increased use of antibiotics for acute travellers' diarrhoea.

Adults are mostly affected but children can also be affected, and there is no predilection for race or gender, according to Patient.info.

Both sources describe a pattern. It often starts with an acute episode of diarrhoea, fever and feeling unwell, and settles into a longer phase of milder diarrhoea, nausea, poor appetite, abdominal cramps and tiredness. Greasy, foul-smelling, pale and bulky stools (steatorrhoea) are common. Nutritional deficiencies, especially of folate and vitamin B12, develop after several months to years.

• Diarrhoea, which may be acute or chronic.

• Weight loss and poor appetite.

• Pale, bulky, greasy stools.

• Tiredness and, in some people, ankle swelling from low blood albumin.

• Signs of deficiency: a sore smooth tongue (glossitis), pallor, scaly skin (vitamin A), bone pain and tingling (vitamin D and calcium), and bleeding tendency (vitamin K).

• In children, delay in skeletal maturity, rickets and growth failure.

Persistent diarrhoea, weight loss or tiredness after living in or travelling to a tropical area should be assessed by a GP, even if the trip was some time ago. Tell the doctor where and when you travelled or lived. NHS 111 can advise if you are unsure how urgently you need to be seen.

Patient.info lists a full blood count and vitamin levels among the first investigations, because anaemia and vitamin deficiency are common in this condition.

The MSD Manual says tropical sprue is suspected in people who live in or have visited endemic areas and have megaloblastic anaemia and symptoms of malabsorption. The test of choice is upper gastrointestinal endoscopy with small-bowel biopsy, and blood tests screen for the effects of malabsorption. Coeliac disease and parasitic infection must be ruled out. Unlike in coeliac disease, the coeliac antibody blood tests are negative in tropical sprue.

Patient.info lists a full blood count, which may show macrocytic anaemia with low folate and vitamin B12 in 60%, and tests of potassium, iron, albumin, vitamin D, calcium and phosphate. Stool is checked for cysts, ova and parasites. A jejunal biopsy shows incomplete villous atrophy, as opposed to coeliac disease where there is complete villous atrophy. Other conditions considered include infections with parasites such as giardia, Crohn's disease, gut tuberculosis, pancreatic disease and AIDS enteropathy.

Patient.info lists fluid and electrolyte replacement, an antibiotic and nutritional supplements. The MSD Manual says treatment is tetracycline for up to 6 months, depending on severity and response, with doxycycline an alternative, oral folate for the first month and vitamin B12 injections for several weeks. It says the clinical response can be dramatic and failure to respond after 4 weeks suggests another condition.

Patient.info says that untreated, the disease runs a chronic, relapsing course and that treatment is associated with a good prognosis. The MSD Manual notes that relapse can occur after successful treatment.

Treatment is monitored by improvement of symptoms such as return of appetite, weight gain, and improvement in blood counts and biochemistry, according to Patient.info. Patient.info also notes that there is no established way to prevent the disease while visiting risk areas, but observing safe practices with drinking water and unpeeled raw vegetables may minimise exposure.

On the NHS, assessment usually begins with a GP, who can arrange blood and stool tests and refer to gastroenterology for endoscopy and biopsy. Because the condition is rare in the UK, it is helpful to give a clear travel history so that parasites and coeliac disease can be considered first.

Private care can offer quicker access to endoscopy and a specialist in tropical medicine or gastroenterology. The tests and treatments are the same. Take any results from overseas with you, as they can shorten the work-up.