Whats new in global infectious diseases? Strongyloidiasis and syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Strongyloidiasis is a parasitic disease caused by the larval stage of intestinal nematode Strongyloides stercoralis. Humans are infected when the third-stage filariform larvae present in contaminated soil or water penetrate the skin and reach venous circulation, then migrate through the blood to the lungs and ultimately to the intestinal tract. Infections with S. stercoralis usually lead to cutaneous, gastrointestinal or pulmonary symptoms. Up to 100 million, strongyloidiasis are reported from 70 countries in tropical and subtropical regions.[12]

Hyperinfection describes the syndrome accelerated autoinfection, commonly the results of an alternation in immune situation. Hyperinfection syndrome indicates the presence of signs and symptoms ascribable to increased larval migration. The finding of increased numbers of larvae in stool is the hallmark of hyperinfection. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is included by different dysfunctions and infection is thought to be one of important etiological of this disease such as strongyloidiasis. Sever anorexia, abdominal pain and constipation may provoke small intestinal obstruction, the consequences of laparotomy can be jeopardous. Alternatively, it may masquerade as a malabsorption disorder with or without clinical evidence of obstruction.[3]

In most patients, in whom this syndrome has occurred, cases were receiving corticosteroids or other immunosuppressive drugs. Disseminated strongyloidiasis frequently develops in patients with immunodeficiencies caused by poor nutrition and drug therapy (including steroid therapy) for autoimmune diseases. These associations suggest that autoinfection may arising as a result of a defect in cell-mediate immunity.[4]

Diagnosis of S. stercoralis infection may be difficult due to the lack of sensitivity (75.9%) of a single direct stool microscopy examination, but the sensitivity raise up to 92% following multiple stool samples or multiple duodenal fluid aspirates. Biopsy can also be used to make a positive identification. The uses of modern techniques include molecular-base method (polymerase chain reaction [PCR]), enzyme-linked immunosorbent assay (ELISA)-based immunoassay and luciferase immunoprecipitation system assays have improved the sensitivities tremendously.[5]

On the basis of their findings, the author(s) presented a case of a 76-year-old man with SIADH that caused by filariform larvae of S. stercoralis. Columbian patient's stay in United States nearly to two decades and had visited from Venezuela, where the strongyloidiasis is endemic. The patient was known to have idiopathic thrombocytopenic purpura (ITP), that is an autoimmune disease with signs include the formation bruises (purpura) and petechiae. He was treated with corticosteroids. Examinations revealed a leukocytosis with a normal eosinophil. Biochemistry data showed a hyponatremia and also laboratory abnormalities of total protein and albumin levels. Histopathological findings revealed infestation of the mucosal epithelium with numerous S. stercoralis larvae. Stool examination demonstrated many S. stercoralis filariform larvae. After treatment with 12 mg of ivermectin, the abdominal symptoms subsided and the serum sodium returned to normal ranges.

To date only a few reports have indicated on this issue[678] and from this point of view, further evidence should be helpful. However, I have some concerns on key methodological aspects.

Rapid diagnosis and treatment of hyperinfection syndrome is essential for patient survival. In this respect, the diagnosis of intestinal strongyloidiasis requires the identification of the larvae in stool or duodenal fluid aspirates. The larvae must be examined for their characteristic morphologic features. This stage usually elicits species-specific patterns of antibodies that have been typed by ELISA. The use of a Strongyloides –specific antigen (NIE) has improved the specificity of this ELISA-based immunoassay. Moreover, molecular diagnostic (e.g., reverse transcription-PCR) is a highly specific tool with improved sensitivity compared with microscopy. Therefore, the most important limitation in the interpretation of the presented this case is that due to not using of these techniques particularly molecular methods identify of species is difficult.

The organism is a recognized cause of pulmonary infection and also disorder of the central nervous system. Therefore, detection of larvae in extraintestinal sites such as bronchoalveolar lavage or cerebrospinal fluid can also be used to make a positive identification.

Finally, I would like to draw attention to possibility of encountering strongyloidiasis in endemic regions and that these cases taking corticosteroids must be high risk for hyperinfection syndrome and the use of modern techniques have great importance for the diagnosis of disease.