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Strongyloidiasis


Strongyloidiasis is a disease caused by a soil-transmitted nematode. It is the result of free living filariform larvae penetrating the human host skin to initiate infection and migrating to the small intestine where they lay their eggs. Larvae are passed in the stool and can cause autoinfection, contributing to lifelong carriage. It is commonly acquired in tropical and subtropical areas, but cases also occur in temperate areas.

It is often asymptomatic but can be associated with mild abdominal symptoms including bloating, pain, diarrhoea and constipation. In mild disease, it can also cause a dry cough and skin rashes. Strongyloidiasis is an occasional cause of Loeffler’s syndrome and, in fulminating cases, may cause secondary bacterial septicaemia or meningitis. Rarely, hyperinfection syndrome can occur, which is life-threatening. Patients on immunosuppressive agents, transplant recipients, or those co-infected with HTLV-1 are at greater risk of this.

Testing for Strongyloides is indicated for the investigation of eosinophilia or if there is a good clinical history to suggest strongyloidiasis.

 

Diagnosis of Strongyloides by microscopy

  • Sample type: Standard stool sample.

Faecal specimens should NOT be refrigerated before sending if Strongyloides culture is required.

Direct observation of Strongyloides larvae is achieved by faecal microscopy and stool culture. The larvae may not be present in every specimen.

  • Sample type: duodenal/jejunal aspirates, BAL (bronchoalveolar lavage) and Sputum

Strongyloides larvae (and adults) can also be demonstrated in the above samples. Sputum may be useful in cases of hyperinfestation. None of these samples will be analysed by culture.


Diagnosis of Strongyloides by serology

  • Sample type: A minimum of 0.5ml of serum is required.

There is known to be cross reaction between filaria and strongyloides antibody in ELISA tests.

Strongyloides serology may be negative in cases of strongyloides hyperinfestation.

After treatment, we do not recommend follow up serology until at least a year after treatment.