Disseminated strongyloidiasis in AIDS and non-AIDS immunocompromised hosts: diagnosis by sputum and bronchoalveolar lavage

Strongyloides stercoralis Infection in Humans: A Narrative Review of the Most Neglected Parasitic Disease

Strongyloidiasis is a helminth infection affecting 613.9 million people annually, mainly in the tropics and subtropics. The reported seroprevalence in the United States is 4% with most of the cases reported in immigrants. Human T-lympho-tropic virus 1 (HTLV-1) infections, hypogammaglobulinemia, immunosuppressant use - particularly steroid use, alcoholism, and malnutrition have been associated with an increased risk of strongyloidiasis. Recently, cases of strongyloidiasis hyperinfection syndrome have been described in coronavirus disease 2019 (COVID-19) patients treated with steroids as well. This brief review discusses the epidemiology, clinical features, management, and prevention of strongyloidiasis including some facts about the infection in pregnancy, transplant recipients, and COVID-19 patients. We conducted an online search using the PubMed, Scopus, and Google Scholar databases. Strongyloidiasis can be asymptomatic or present with mild symptoms. Strongyloides stercoralis is known to cause autoinfection. In immunocompromised individuals, it can present with severe symptoms, hyperinfection, or disseminated disease. Reported mortality in cases of disseminated Strongyloidiasis is 87.1%. Serology and detection of larvae in stool by direct microscopy are the most commonly used methods to diagnose strongyloidiasis. The drug of choice for the treatment is ivermectin. However, the use of ivermectin in human pregnancy is not well studied, and its teratogenic risks are unknown. Proactive screening of strongyloidiasis is necessary in immunocompromised individuals to prevent severe disease.

Parasite-bacteria interrelationship

Parasites and bacteria have co-evolved with humankind, and they interact all the time in a myriad of ways. For example, some bacterial infections result from parasite-dwelling bacteria as in the case of Salmonella infection during schistosomiasis. Other bacteria synergize with parasites in the evolution of human disease as in the case of the interplay between Wolbachia endosymbiont bacteria and filarial nematodes as well as the interaction between Gram-negative bacteria and Schistosoma haematobium in the pathogenesis of urinary bladder cancer. Moreover, secondary bacterial infections may complicate several parasitic diseases such as visceral leishmaniasis and malaria, due to immunosuppression of the host during parasitic infections. Also, bacteria may colonize the parasitic lesions; for example, hydatid cysts and skin lesions of ectoparasites. Remarkably, some parasitic helminths and arthropods exhibit antibacterial activity usually by the release of specific antimicrobial products. Lastly, some parasite-bacteria interactions are induced as when using probiotic bacteria to modulate the outcome of a variety of parasitic infections. In sum, parasite-bacteria interactions involve intricate processes that never cease to intrigue the researchers. However, understanding and exploiting these interactions could have prophylactic and curative potential for infections by both types of pathogens.

Lung Infections

A review of pulmonary infections of all types with diagnostic and morphological features.

Strongyloides Stercoralis Infection Among Human Immunodeficiency Virus (HIV)-Infected Patients in the United States of America: A Case Report and Review of Literature

Patient: Male, 61

Final Diagnosis: Strongyloides stercolaris-associated diarrhea

Symptoms: Diarrhea • epigastric pain • nausea • weight loss

Medication: Ivermectin

Clinical Procedure: Colonic biopsies

Specialty: Infectious Diseases

Human infection with Strongyloides stercoralis and other related Strongyloides species

The majority of the 30-100 million people infected with Strongyloides stercoralis, a soil transmitted intestinal nematode, have subclinical (or asymptomatic) infections. These infections are commonly chronic and longstanding because of the autoinfective process associated with its unique life cycle. A change in immune status can increase parasite numbers, leading to hyperinfection syndrome, dissemination, and death if unrecognized. Corticosteroid use and HTLV-1 infection are most commonly associated with the hyperinfection syndrome. Strongyloides adult parasites reside in the small intestine and induce immune responses both local and systemic that remain poorly characterized. Definitive diagnosis of S. stercoralis infection is based on stool examinations for larvae, but newer diagnostics - including new immunoassays and molecular tests - will assume primacy in the next few years. Although good treatment options exist for infection and control of this infection might be possible, S. stercoralis remains largely neglected.

Strongyloidiasis with emphasis on human infections and its different clinical forms

Strongyloidiasis (caused by Strongyloides stercoralis, and to a lesser extent by Strongyloides fuelleborni) is one of the most neglected tropical diseases with endemic areas and affecting more than 100 million people worldwide. Chronic infections in endemic areas can be maintained for decades through the autoinfective cycle with the L3 filariform larvae. In these endemic areas, misdiagnosis, inadequate treatment and the facilitation of the hyperinfection syndrome by immunosuppression are frequent and contribute to a high mortality rate. Despite the serious health impact of strongyloidiasis, it is a neglected disease and very little is known about this parasite and the disease when compared to other helminth infections. Control of the disease is difficult because of the many gaps in our knowledge of strongyloidiasis. We examine the recent literature on different aspects of strongyloidiasis with emphasis in those aspects that need further research.

Respiratory Tract and Mediastinum

Normal cytology, abnormal and atypical cells, non-cellular components, and infectious cell changes are largely described together with benign, malignant, and neuroendocrine lesions regarding exfoliative and aspiration cytology of the lung. A separate section broadly addresses diagnostic findings and differential diagnoses in bronchoalveolar washings.

The section ‘Fine needle aspiration biopsy of mediastinal disorders’ covers in particular biopsy techniques, accuracy of liquid-based cytology, and the complex lesions of the thymus gland. Cytodiagnostic algorithms of the major benign and malignant pulmonary and mediastinal lesions and their respective differential diagnoses are additionally presented in synoptic setups.

Strongyloides stercoralis hyperinfection syndrome after liver transplantation: case report and literature review

Strongyloides stercoralis is an intestinal nematode that causes human infections and whose life cycle has special features, including autoinfection. Strongyloides infection may be asymptomatic for years, owing to a low parasite load. During immunosuppressive therapy, however, if cellular immunity is depressed, autoinfection can occur at a higher rate, resulting in hyperinfection syndrome. In this specific circumstance, it can become a fatal illness. We describe a case of hyperinfection syndrome in a liver transplant recipient and also review the literature.

[Finding of Strongyloides stercoralis infection, 25 years after leaving the endemic area, upon corticotherapy for ocular trauma]

In the field of ophthalmology, indications for high-dose corticotherapy are various. This paper reports the case of a Caledonian man who presented with intestinal strongyloidiasis, discovered 25 years after he had left the endemic area. A checkup before corticotherapy for traumatic retina edema provided the diagnosis of the infection. The authors emphasize the importance of searching for Strongyloidiasis stercoralis larva before initiating corticotherapy, as it is the main treatment responsible for parasitic dissemination. The most severe form of strongyloidiasis, the disseminated form, has a high mortality rate: 70%-90%. The definitive diagnostic test is enhanced larva recovery, which should be proposed to every patient returning from endemic area, people with precarious hygiene or with high eosinophilia or intestinal symptoms of chronic infection. Delay in diagnosing strongyloidiasis frequently results in death, despite vigorous treatment.

[Intestinal and disseminated strongyloidosis: two case studies]

Systemic strongyloidiasis is a rare but serious complication of intestinal strongyloidiasis. This condition occurs mainly in immunosuppressed patients and has a significant mortality rate. The use of immunosuppressive and cytotoxic treatment has increased its incidence. A better awareness of this infection with early diagnosis and treatment is essential. We report two cases of strongyloidiasis. The first, uncomplicated intestinal strongyloidiasis occurred in a 32-year-old HIV-positive women. The second case was fatal disseminated strongyloidiasis in a 14-year-old child who underwent prior surgery and radiotherapy with cortico sterpoid therapy for a malignant brain ganglioglioma. The pathological basis of intestinal and disseminated strongyloidiasis are discussed.

Intestinal strongyloidiasis: recognition, management, and determinants of outcome

Significant advances have occurred in our understanding of the biology, immunology, and immunopathology of the usually asymptomatic human infection by the intestinal parasite, Strongyloides stercoralis. Factors that increase the risk for the occurrence of symptomatic intestinal hyperinfection and/or often-fatal disseminated strongyloidiasis have been better defined. The pathophysiology underlying these risk factors, whether disease-related or iatrogenically induced, is a compromised immune system leading to dysfunction of TH-2 helper cells. These specialized lymphocytes are central to maintaining the delicate balance that exists between the infected human host and the stabilized parasite. Recognition of risk factors that impair the function of TH-2 lymphocytes is essential to heightening the index of clinical suspicion enhancing earlier, accurate diagnosis, and the introduction of appropriate therapy. This review summarizes what is understood about infection by S. stercoralis; its focus will be on the epidemiology, diagnosis, clinical presentation patterns in the immunocompetent and immunocompromised human hosts, and recommended treatment regimens.

Pulmonary Strongyloidiasis: The Varied Clinical Presentations

Strongyloides stercoralis is a unique parasite. It can complete its life cycle entirely within the human host. As a result, an autoinfection cycle is set up. As long as there is an intact immune system, the host can control the parasitic burden, and the organism may persist for years after the initial inoculum. Most infected individuals experience mild gastrointestinal or pulmonary symptoms that may fluctuate for years. When cell-mediated immunity becomes impaired (ie, corticosteroid use, malignancy, acquired immunodeficiency syndrome), the parasite burden will grow, disseminate, and cause hyperinfection. Strongyloidiasis is endemic in the tropical and subtropical areas of the world; additionally, it is also endemic in the southeastern United States. Strongyloidiasis is associated with asthma, preexisting lung disease, and immunosuppression, including acquired immunodeficiency syndrome. Eosinophilia is not a prerequisite; therefore, the diagnosis of strongyloidiasis requires a high index of suspicion.

Strongyloides stercoralis in the Immunocompromised Population

Strongyloides stercoralis is an intestinal nematode of humans that infects tens of millions of people worldwide. S. stercoralis is unique among intestinal nematodes in its ability to complete its life cycle within the host through an asexual autoinfective cycle, allowing the infection to persist in the host indefinitely. Under some conditions associated with immunocompromise, this autoinfective cycle can become amplified into a potentially fatal hyperinfection syndrome, characterized by increased numbers of infective filariform larvae in stool and sputum and clinical manifestations of the increased parasite burden and migration, such as gastrointestinal bleeding and respiratory distress. S. stercoralis hyperinfection is often accompanied by sepsis or meningitis with enteric organisms. Glucocorticoid treatment and human T-lymphotropic virus type 1 infection are the two conditions most specifically associated with triggering hyperinfection, but cases have been reported in association with hematologic malignancy, malnutrition, and AIDS. Anthelmintic agents such as ivermectin have been used successfully in treating the hyperinfection syndrome as well as for primary and secondary prevention of hyperinfection in patients whose exposure history and underlying condition put them at increased risk.

[Strongyloides stercoralis infection in patients with bronchial obstructive pathology]

Strongyloides stercoralis infection was hardly seen in Spain until a few years ago but has recently been shown to be fairly common in some geographic areas. In the respiratory tract this germ can cause acute bronchospasms that make diagnosis difficult, particularly in patients with underlying bronchial disease. To determine if curing S. stercoralis infection is accompanied by clinical and functional improvement in patients with bronchial obstruction, we studied the evolution of 22 infected patients: 11 with no bronchopulmonary disease and 11 with chronic airway obstruction or asthma. The following variables were assessed in both groups at the moment of diagnosis of infection and four months after cure: levels of eosinophils and total serum IgE, respiratory symptoms, steroid doses and spirometric parameters. After four months we observed a significant decrease in eosinophil (16 versus 5%) and IgE (1,600 versus 770 IU/ml) levels in both groups. The number of bronchospasms and daily steroid doses required decreased in the group with bronchial disease. No significant differences were seen in spirometric parameters, however. The improvement in respiratory symptoms, blood parameters and need for medication leads us to believe that airway inflammation decreases after the infection has been eradicated, in spite of the lack of improvement in bronchial obstruction.

Viruses and other miscellaneous organisms

Pulmonary infections caused by several types of viruses and other miscellaneous organisms may cause disease in HIV infection. Evidence suggests that pulmonary conditions may result from infections of the lung by HIV itself. Other viruses, most commonly cytomegalovirus, may be primary perpetrators of pneumonitis or may contribute to diseases caused by coexisting infections. Although diagnosis and assessment of the clinical significance of these infections may be difficult, their recognition is of practical importance because potentially effective therapeutic agents are available for several of them. Miscellaneous infections such as pulmonary toxoplasmosis and pertussis are other uncommon but potentially treatable complications of HIV disease.

Fulminant, systemic strongyloidiasis in AIDS

The 15th known case of systemic Strongyloidiasis in an AIDS patient is recorded, with emphasis on the fulminant clinical cause and diffuse organ involvement.

Strongyloides stercoralis eosinophilic granulomatous enterocolitis

Six patients suffering from an unusual form of colitis produced by Strongyloides stercoralis hyperinfection are described. In contrast to the usual Strongyloides hyperinfection syndrome, in which small intestinal and pulmonary manifestations are seen in patients with some forms of immunodeficiency, the patients described here presented with only a characteristic transmural eosinophilic granulomatous inflammation affecting mostly the colonic wall and clinically mimicking ulcerative colitis or Crohn's disease. This Strongyloides eosinophilic granulomatous enterocolitis apparently results from a florid inflammatory response by eosinophils, histiocytes, and giant cells with formation of granulomas that destroy the larvae entering the colon. This morphologic picture differs from that of the well-described hyperinfection syndrome, in which the bulk of the larvae pass through the colonic wall to complete the life cycle, with only a few larvae destroyed in the colon. The probable pathophysiologic mechanism of this unusual manifestation of hyperinfection is discussed based on the anatomic and clinical observations of patients who presented at different stages in the evolution of their condition and whose length of follow-up varied.

Case report: strongyloidiasis refractory to treatment with ivermectin

Strongyloides stercoralis usually causes chronic asymptomatic infection in humans. However, in patients with AIDS, malignancy, and individuals receiving corticosteroids, disseminated infection can develop, associated with an extremely high mortality rate and frequent treatment failure with thiabendazole. Recently, ivermectin was found to be very effective in such patients. The authors report a case of strongyloidiasis in a patient with hypogammaglobulinemia in which ivermectin failed to clear Strongyloides larvae from stool, despite repeated courses of treatment throughout 14 months.

Disseminated strongyloidiasis with cutaneous manifestations in an immunocompromised host

Recognition of the characteristic cutaneous eruption of disseminated strongyloidiasis can be crucial for early diagnosis and treatment of this potentially fatal infestation. We describe a corticosteroid-dependent elderly man who had a purpuric eruption. Filariform larvae of Strongyloides stercoralis were found in dermal granulomas and also in the sputum.

Disseminated Strongyloides stercoralis in human immunodeficiency virus-infected patients. Treatment failure and a review of the literature

We describe a North American human immunodeficiency virus (HIV)-positive patient with Strongyloides stercoralis infection of the gastrointestinal tract, who required repeated "standard" courses of thiabendazole. Pulmonary infection with numerous roundworms developed, as suspected by bronchoalveolar lavage, and while he was receiving therapy, dissemination occurred. On autopsy, S stercoralis was recovered in the gastrointestinal tract, liver, lung, and heart. After a literature review, we conclude that HIV-positive patients have a higher risk of dissemination and "standard" treatment failure. This may occur without elevation of IgE or eosinophilia. Those patients may require prolonged courses of thiabendazole or alternatively ivermectin therapy.