Summary about Disease
Strongyloidiasis is a parasitic disease caused by the nematode worm Strongyloides stercoralis. It's prevalent in tropical and subtropical regions. The unique aspect of this infection is its ability to persist within the host for decades through autoinfection, where larvae mature internally and re-infect the host. This can lead to chronic infection and, in immunocompromised individuals, a life-threatening disseminated disease called hyperinfection syndrome.
Symptoms
Symptoms can vary widely, ranging from asymptomatic infection to severe illness. Common symptoms include:
Skin: Itchy rash (especially around the buttocks and waist), larva currens (rapidly migrating linear rash)
Gastrointestinal: Abdominal pain, diarrhea, nausea, vomiting, constipation, loss of appetite
Respiratory: Cough, wheezing, shortness of breath (especially during larval migration through the lungs)
Disseminated disease (hyperinfection): Septicemia, pneumonia, meningitis, multi-organ failure
Causes
Strongyloidiasis is caused by infection with the nematode worm Strongyloides stercoralis. The infection occurs when filariform larvae (infective stage) penetrate the skin, typically through contact with contaminated soil. These larvae migrate through the bloodstream to the lungs, then travel up the trachea, are swallowed, and mature into adult worms in the small intestine. The female worms lay eggs that hatch into larvae, which are then excreted in the stool or can cause autoinfection.
Medicine Used
The primary medications used to treat strongyloidiasis are:
Ivermectin: Typically the first-line treatment.
Albendazole: An alternative treatment option, but generally less effective than ivermectin. Treatment duration and dosage depend on the severity of the infection and the patient's immune status. For disseminated disease, prolonged or repeated courses of treatment may be necessary.
Is Communicable
Strongyloidiasis is generally not directly communicable from person to person. The typical mode of transmission is through contact with soil contaminated with filariform larvae. However, autoinfection allows the infection to persist within a single host for extended periods. In rare cases, transmission can occur through organ transplantation or from mother to child during pregnancy or childbirth.
Precautions
Precautions to prevent strongyloidiasis include:
Avoid walking barefoot in areas where the parasite is common.
Practice good hygiene, including washing hands frequently with soap and water, especially after contact with soil.
Improve sanitation by ensuring proper disposal of human waste.
Avoid contact with soil that may be contaminated with human feces.
Wear shoes and protective clothing when working in agricultural settings or engaging in activities that involve contact with soil.
Screening: High-risk individuals (e.g., those from endemic areas, those who will be treated with immunosuppressants) should be screened.
How long does an outbreak last?
Unlike many other infectious diseases, Strongyloidiasis does not typically present as an "outbreak" in the traditional sense. Because the infection is acquired through environmental exposure, it is more common to see sporadic cases or clusters of cases within specific communities where sanitation and hygiene are poor. The duration of infection within an individual can be chronic (years or decades) due to autoinfection if left untreated. The presence of Strongyloides in an area may remain for a very long period unless drastic public health intervention removes it.
How is it diagnosed?
Diagnosis of strongyloidiasis can be challenging. Tests include:
Stool examination: Microscopic examination of stool samples for larvae. Multiple samples may be needed due to intermittent shedding of larvae.
Serology: Blood tests to detect antibodies against Strongyloides stercoralis. Serology can be helpful, but false negatives and false positives can occur.
Duodenal aspirate or biopsy: Examination of samples from the small intestine for larvae or adult worms. This is more invasive and typically reserved for cases where stool examination and serology are negative, but strong suspicion remains.
Sputum examination: In cases of pulmonary involvement, sputum samples may be examined for larvae.
Agar plate culture: A technique that can increase the sensitivity of detecting larvae in stool samples.
Timeline of Symptoms
The timeline of symptoms can be variable:
Initial infection: Skin penetration by larvae may cause a brief, localized itchy rash.
Larval migration: As larvae migrate through the lungs, respiratory symptoms (cough, wheezing) may develop within days to weeks.
Intestinal phase: Gastrointestinal symptoms (abdominal pain, diarrhea) may appear weeks to months after infection.
Chronic infection: Many individuals remain asymptomatic for years. Autoinfection maintains a low level of parasitic burden.
Hyperinfection: In immunocompromised individuals, the infection can disseminate rapidly, leading to severe symptoms and potentially death within days to weeks.
Important Considerations
Immunocompromised patients: Strongyloidiasis can be particularly dangerous in individuals with weakened immune systems (e.g., those receiving corticosteroids, transplant recipients, HIV-infected individuals). Disseminated disease (hyperinfection syndrome) is a major risk in this population.
Screening before immunosuppression: Individuals from endemic areas or with a history of exposure to potentially contaminated soil should be screened for strongyloidiasis before starting immunosuppressive therapy.
Autoinfection: The ability of Strongyloides to autoinfect makes treatment challenging and requires careful monitoring to ensure eradication of the parasite.
Eosinophilia: Although not always present, eosinophilia (elevated levels of eosinophils in the blood) is a common finding in strongyloidiasis. However, its absence does not rule out the infection.
Geographic distribution: Be aware of the endemic areas and travel history of the patient.