Hyperinfection with Strongyloides in a HIV-negative elderly male.

Strongyloides stercoralis is an intestinal nematode producing mild infection in the immunocompetent and fatal hyperinfection syndrome in the immunocompromised. An elderly HIV-negative male presented with symptoms of chronic respiratory disease and vague abdominal symptoms. Examination of sputum and stools showed larvae of S. stercoralis. Bacterial and fungal causes of respiratory infections were ruled out. The patient responded to oral ivermectin.

INTRODUCTION

Strongyloides stercoralis is a soil-transmitted intestinal nematode which is widely distributed throughout the tropics and subtropics. Infection usually results in asymptomatic chronic disease of the gut.[1] Autoinfection can lead to persistence of the disease and hyperinfection syndrome in patients with impaired cell-mediated immunity.[2] Immunosuppressive therapy, particularly with steroids, malnutrition, malignancy and chemotherapeutic agents may precipitate the occurrence of fatal hyperinfection syndrome.[3] Definitive diagnosis depends on the demonstration of larvae in the feces or duodenal aspirate. Early diagnosis and treatment can prevent the onset of the fatal forms of hyperinfection and disseminated disease.

CASE REPORT

A 70-year-old male was brought to the emergency department with complaints of increasing difficulty in breathing, cough with expectoration and fever of about one-week duration. The patient was suffering from cough with expectoration, breathlessness on and off for the past two years and vague abdominal discomfort for the past six months. The patient was not a diabetic or hypertensive but smoker for the past 40 years. On examination, the patient was thin built, ill-looking and pale. His pulse rate was 86/min and blood pressure was 140/80 mm of Hg. On palpation, the abdomen was tender in the epigastric and right hypochondriac region. There was no evidence of lymphadenopathy. Papules and excoriations were seen over the perianal region. The patient was conscious and coherent. No abnormality of central nervous system (CNS) was noted. Normal vesicular breathing with rales and course crackles were found in both the lung fields. Examination of cardiovascular system (CVS) was unremarkable.

At the time of admission, random blood sugar was 85 mg/dl, blood urea - 44 mg/dl, creatinine - 4 mg/ dl, hemoglobin - 9.3 g/dl, total count - 7200 cells/cmm, differential count- P67%, L29%, E04%, absolute esinophil count - 480 cells/cmm, erythrocyte sedimentation rate -10 mm and 24 mm at half an hour and one hour respectively. Serum sodium was 123 mmol/l, serum potassium - 3.3 meq/l, chloride - 89 meq/l and bicarbonates- 26 meq/l. Mantoux test and test for anti-human immunodeficiency virus (HIV) antibodies were negative. Electrocardiogram showed sinus tachycardia. Chest X-ray was suggestive of multiple fluid-filled cavities in the left lung and pending the results of sputum examination, the patient was empirically put on injection deriphylline, amoxycillin-clavulanic acid, gentamicin, ranitidine and metronidazole with a provisional diagnosis of acute exacerbation of chronic obstructive pulmonary disease (COPD)/lung abscess.

On day three of admission, the patient continued to have difficulty in breathing. Physical examination showed bilateral wheeze and no other abnormality. Electrocardiogram (ECG) showed sinus tachycardia. The patient was put on increasing dose of bronchodilators following which he appeared to be relieved temporarily. SPO2 was 96% without O2 Sputum for acid fast bacilli (AFB) was negative on three consecutive days. Wet mount of the sputum showed plenty of actively motile larvae of S. stercoralis [Figure 1a, Video 1]. Routine culture of sputum yielded a moderate growth of Escherichia coli which was susceptible to gentamicin and amikacin. Examination of stool and repeat sputum was requested by our laboratory following the detection of larvae in the sputum. Stool sample and sputum sample collected on two consecutive days showed plenty of motile larvae of S. stercoralis [Figure 1b]. The patient was put on albendazole 400 mg bid for three days. Repeat chest X-ray showed persistence of lung abscess on the left side. Ivermectin 12 mg OD was subsequently added to the treatment regimen and albendazole continued for further three days. Repeat stool examination done on the two consecutive days did not show any larvae of S. stercoralis. Sputum could not be examined as the patient could not submit the sample as there was no expectoration. Repeat chest X-ray showed clearance of fluid in the lung abscess with only thick fibroid wall of the cavity. He became afebrile and appetite improved. The patient was feeling better and was discharged at request with advice to report after two weeks. Follow-up of the patient four weeks later showed the patient was asymptomatic and stool examination did not show any parasites.

Figure 1

(a) Iodine mount of the sputum showing larvae of S. stercoralis and many pus cells under ×45. (b) Iodine mount of the stool showing larvae of S. stercoralis under ×45

DISCUSSION

S. stercoralis is a unique intestinal nematode capable of causing chronic asymptomatic infection or hyperinfection and dissemination due to its ability to produce autoinfection in the intestine and due to penetration of the perianal skin by the filariform larvae.[12] Disseminated strongyloidiasis occurs often in the immunocompromised due to disease or therapy with steroids.[3] Other risk factors include age more than 65 years, chronic lung disease, chronic debility and use of histamine blockers for gastric acidity.[4] Although infection is common in tropical regions, hyperinfection leading to acute respiratory distress syndrome (ARDS) is rare.[5] Massive auto-infection may manifest as asthma, chronic bronchitis, hemoptysis, eosinophilia and pulmonary infiltrates.[67] Pulmonary strongyloidiasis is a common manifestation of the Strongyloides hyperinfection syndrome.[8] Air space consolidation, pleural effusion, pulmonary hemorrhage, lung abscess and ARDS have been reported with strongyloidiasis.[9-11]

In the case reported here the patient presented with symptoms of COPD with acute exacerbation. A KOH wet mount of the sputum done to exclude fungal etiology led to the detection of larvae of S. stercoralis and thus a clinical diagnosis of pulmonary strongyloidiasis associated with hyperinfection syndrome was made. Since the consecutive sputum, stool samples examined subsequently on two consecutive days showed plenty of larvae of S. stercoralis the diagnosis was confirmed. The isolation of E. coli from the sputum sample was in all possibility due to the organism being carried by the larvae during their migration from the intestine to the lungs via the bloodstream as part of their course of travel following internal autoinfection. The lung abscess and associated changes could probably be due to E. coli and hypersensitivity reactions to the larval forms in the lung.[10] Strongyloidiasis should be included in the differential diagnosis of all long-term symptomatic chest diseases with risk factors including the elderly and malnourished.[12]

Infection with Strongyloides is lifelong and reactivation can occur decades after primary infection. Pulmonary strongyloidiasis should also be suspected in all patients with asthma who are on steroids if their symptoms worsen or fail to respond to conventional treatment with bronchodilators and/or steroids. It is advisable to screen stool samples of all patients on steroids or immunosuppressive agents for any therapeutic purpose at regular intervals and also sputum or bronchoalveolar lavage samples if available in symptomatic chest diseases for early diagnosis of a potentially fatal but a treatable condition. Serological test for demonstration of antibodies is also a useful and sensitive test, particularly in the follow-up of treated cases. A high index of clinical suspicion is necessary and should be considered in all critically ill patients with chest symptoms. Initiation of specific therapy with albendazole and/or ivermectin for an adequate period can prove to be lifesaving as in our case.