5 Opportunistic infections (OIs) and coinfections

5.4 Gut infections: giardia, cryptosporidia, microsporidia

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Type of infection

Giardia, cryptosporidia and microsporidia are tiny parasites (protozoa) that can cause stomach upset and severe diarrhoea.

Gut infections are more likely in people with CD4 counts under 300 cells/mm³, and become more common as the CD4 count declines.

Infection is almost always the result of:

• Drinking unfiltered water.
• Swallowing contaminated water when swimming.
• Eating raw vegetables contaminated by food handlers.
• Cryptosporidia is also acquired from drinking unpasteurised milk.

Nappies, daycare facilities, pets, farm animals, and other people may be routes of infection.

Main symptoms

• Persistent diarrhoea that does not resolve within a few weeks.
• Microsporidia can also cause inflammation in other parts of the body including the lungs, bladder, bowel, sinuses, ears, eyes, brain and pancreas.

Diarrhoea and weight loss are often linked because the body is less able to absorb nutrition from food. Severe diarrhoea can also reduce absorption of medication.

Weight loss in HIV-positive people (that is not explained by a change in diet) can be very serious. Any weight loss should be taken seriously

• Unexplained weight loss of 10% over a year is an AIDS-defining illness.
• Unexplained weight loss of 5% over 6 months suggests 10% weight loss later.

Diagnosis

Laboratory tests of a stool sample can look for causes of diarrhoea. The cause can be difficult to identify.

Treatment

There are no universally effective treatments for these infections. HIV treatment with ARVs to increase CD4 count is likely to be the most effective treatment.

• It is important to drink plenty of fluids to help prevent dehydration.
• Anti-diarrhoea medicines like loperamide can help.
• In people with CD4 counts over 300 the body usually flushes out the parasite without treatment within a few weeks.
• In people with CD4 counts under 300 this doesn't always happen and diarrhoea can become chronic.

The antibiotic albendazole has been used to treat microsporidia – as has the drug thalidomide because of its anti-inflammatory effect. The antibiotics azithromycin and paromomycin have been used at high doses to treat cryptosporidia.

Prophylaxis

Ways to minimise risk of these infections for HIV-positive people with low CD4 counts:

• Wash vegetables in bottled or boiled water and peel them carefully.
• Cook meat thoroughly.
• Hygiene (especially washing your hands) is important to avoid becoming infected or spreading infection.

Many parasites that cause GI (gastro-intestinal) upset are linked to faeces – hygiene when caring for pets or children is especially important if you are HIV-positive.