Strongyloidiasis

A parasitosis caused by the intestinal nematode Strongyloides stercoralis (round worm).

Epidemiology

It affects between 30 and 60 millions people worldwide and is endemic to sub-tropical zones including Africa, the West Indies, Central and South America, the Indian Ocean region, South East Asia.

Clinical description

Acute infection is characterized by cutaneous manifestations such as serpiginous urticarial rash, cough, dyspnea, gastrointestinal symptoms (including pain and soft stools) and allergic manifestations; however over half of infected individuals remain asymptomatic. Strongyloides hyperinfection syndrome (SHS) may occur in patients with underlying illness such as HTLV1 infection or those undergoing corticosteroids or immunosuppressive treatment and often results in sepsis, shock, and acute respiratory distress syndrome. Respiratory, gastrointestinal, cutaneous, and neurologic symptoms are observed at variable frequencies, but the hallmark of SHS is the severity of organ failure requiring ICU admission.

Etiology

The female nematodes, which measure 2.5 mm in length, live in the small intestine of humans. Eggs laid in the small intestine hatch to release larvae that are normally excreted in the feces. On damp ground, these larvae reach their infectious stage directly or after a phase of sexual reproduction. In this infectious form they can penetrate the skin directly. Evolution towards the infectious stage may also take place within the digestive system, explaining the long duration of parasitosis (more than 30 years) observed in some cases.

Diagnostic methods

Diagnosis is made by serological test, agar plate culture or stool examination, the latter of which has low sensitivity and requires a minimum of three samples.

Differential diagnosis

Differential diagnosis may include ancylostomiasis and other causes of gastritis, enteritis, bronchitis, and dysentery.

Management and treatment

Access to clean water, footwear, and sanitation is fundamental to preventing new cases of strongyloidiasis. The treatment of choice is ivermectin. Disseminated infections may require intensive care.

Prognosis

Lifelong infection is possible if left untreated. Most patients remain asymptomatic even with chronic disease, but prognosis depends on development of complications. Disseminated infection is fatal in 60-70% of cases.