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The topic was a case presentation and discussion of a case of probable Strongyloidiasis.

The patient was a 58 year old aboriginal woman with 2 month history of increasing abdominal distension associated with dyspnea and leg edema. She had a past history of obesity, hypertension, diabetes mellitus and IHD - anterior AMI 9/95 with CABG in 2/96 and subsequent poor LV function. In 1/97 she had a similar presentation to the above which responded poorly to diuretics. She had abnormal LFT's (she did not drink alcohol) and a CT showed evidence of ascites.

A Gastroenterologist arranged admission for ascitic tap and liver biopsy. However the ascites had resolved by the time of admission and no further investigations were done. Medications on admission were aspirin, trandalopril, frusemide(in increasing doses), spironolactone and insulin.

Clinical examination showed markedly elevated JVP c/w tricuspid incompetence, mitral regurgitation, gross ascites and leg edema. Biochemistry and hematology were consistent with her clinical findings, although she had an absolute eosinophil count of up to 2000(N<500). A large volume paracentesis was done for symptom relief and the surprising finding was a protein level of 38Gms/L c/w an exudate and cytology showing a moderate degree of mononuclear inflammation. The patient subsequently mentioned that she had been non-specifically unwell for months with intermittent cough and diarrhea. She had seen a GP when she was in Melbourne a few months previously and reported that a parasite had been found in her stool. This result was unable to be tracked down. As the patient had resided in Asia for some years her Strongyloides serology was sent off. She was discharged well and several weeks later her Strongyloides serology came back as strongly positive. Discussion with a parasitologist at Westmead Hospital indicated that this result was strongly suggestive of ongoing infection. He indicated that he had taken part in prevalence surveys in this area in the 1960's which showed hookworm infection rates of 60-90% among aboriginal children. Prevalence of Strongyloides was around 30%.

The Microbiology Department at LBH has only detected 1 case of Strongyloides in stool samples over the last 2 years. This patient was an elderly aboriginal man with end-stage renal failure who died shortly after the parasite was found.

Between 1/97 and 11/99 there were 22 requests to NRPS for serological testing for Strongyloides. There were 19 patients (three were tested twice). There were 8 positives. The index case; an 82 year old aboriginal man admitted with cardiac problems who was noted to have diarrhea and eosinophilia; 4 aboriginal patients with CRF - one of these was diagnosed when she presented with an E.coli septicemia (well known association); an aboriginal woman admitted for elective knee replacement who had the test done because of eosinophilia. The only non-aboriginal was an "old digger" who had served in Asia who had anemia and non-specific GIT symptoms. His serology was negative some months later after treatment.

Strongyloidiasis is a common parasitic infection in the tropics with prevalence rates of up to 15%. It is associated with poverty and insanitary conditions. There are two human pathogens- species stercoralis (what we have here) and fuelleborni. The parasites are approximately 2mm long. They have a complicated life cycle of about 12 days with both parasitic and free-living forms. In the free-living cycle the larvae (or eggs) are passed in the feces and feed on the microflora of fecally-enriched soils. The larvae develop through several stages and may either mate in the soil to produce more eggs/larvae or the third-stage(filariform) larvae may directly penetrate the skin of a host. In this case they migrate through the tissues and end up in the lung where they get coughed up and swallowed and develop into adults in the proximal gut. With the parasitic cycle the larvae migrate directly through the gut wall and then some how get to the lung. Strongyloides is different to most other parasites in that it can replicate within the host. The longest recorded infection is 65 years. The parasitic cycle mentioned above is called internal autoinfection. External autoinfection is where the larvae moult in the perianal region and migrate directly through the skin. This gives rise to the characteristic skin lesion called larva currens.

Human disease is classed as uncomplicated where it is confined to the gut and complicated where there is evidence of remote effects due to the parasite load. There are distinct associations with renal disease, immunosuppression, diabetes, alcoholism, malnutrition and HIV. However far fewer cases are seen in those patients with HIV than would be expected given the prevalence of the two conditions in tropical countries- no-one has explained this. It is also much less common in renal transplant patients now compared to 25-30 years ago - it is postulated that cyclosporin may have an anti-helminthic effect.

Clinical features are non-specific and relate to GIT disturbance. Complicated strongyloidiasis has been associated with bowel obstruction, protein-losing enteropathy, respiratory symptoms (including respiratory failure) as well as meningitis and arthritis. Most patients will have eosinophilia. The diagnosis is made by finding the parasite in the stool or by positive serology. In areas of high prevalence serology is not useful as it remains positive for quite a long time in the absence of active infection.

Treatment is with albendazole 400mgs daily for three days and repeat in one week. Ivermectin can also be used but is usually reserved for life-threatening or relapsing cases. There is a small but significant risk of relapse with both forms of treatment.

The patient presented did not have Strongyloides detectable in her stool on two occasions but was still treated with albendazole. She reports good health since .

Since the initial case I have seen four more - I suspect if we look for it we will find it to still be fairly common.

John Burrell ,JohnBu@doh.health.nsw.gov.au
Staff Specialist Physician