Definition

Strongyloidiasis is an infection caused by the roundworm Strongyloides stercoralis. These worms are commonly found in tropical and subtropical regions with warmer climates. It is estimated that around 30–100 million people are infected with strongyloidiasis worldwide, with an incidence rate of approximately 10% in Indonesia. Typically, strongyloidiasis does not cause specific symptoms. Preventive measures include maintaining personal hygiene.

Causes

Strongyloides stercoralis is the main species from the Strongyloides genus that attacks humans. Approximately 40 other species can infect birds, reptiles, amphibians, livestock, and primates. The larvae of these worms are small, measuring only about 600 µm, making them difficult to see with the naked eye.

Strongyloides stercoralis is classified as a soil-transmitted helminth, which means it spreads through the soil. This means the parasite infects humans through contact with larvae-contaminated soil. When the larvae come into contact with the skin, they can penetrate and migrate throughout the body, eventually reaching the small intestine. In the small intestine, the larvae will grow into adult worms (measuring 2–3 mm) and damage the mucosa of the small intestine. Female worms will deposit their eggs on the intestinal mucosa. In one day, a female worm can lay up to 40 eggs.

Unlike other worms whose eggs cannot hatch in humans, Strongyloides stercoralis eggs can hatch inside the body. Most of the larvae will be expelled through stool, but many will stay in the small intestine and reinfect (autoinfection) by attacking the wall of the small intestine or penetrating the skin around the anus. Autoinfection can cause someone to have continuous infection throughout their life.

In addition to direct contact with soil, the parasite can infect humans through other means, such as:

• Organ transplantation
• Living with individuals with cognitive disabilities who require assistance in daily activities
• Halfway houses
• Daycare centers

Risk factor

Risk factors of Strongyloidiasis include:

• Walking barefoot
• Contact with human feces
• Occupations involving soil, such as agriculture and mining
• Living in tropical areas
• Living in rural areas with poor or inadequate sanitation
• Using human feces as fertilizer

Symptoms

Around 50% of individuals with Strongyloidiasis do not have symptoms. If symptoms do occur, they may include:

• Pain in the upper abdomen
• Diarrhea, or alternating diarrhea with constipation
• Cough
• Moving and spreading skin rash
• Itching on the skin
• Rash around the anus
• Vomiting
• Weight loss
• Mild fever

Rashes can occur after contact with the S. stercoralis worm. Other digestive symptoms typically appear 2 weeks after contact, and new larvae can be detected 3-4 weeks after contact.

Symptoms of Strongyloidiasis can be more severe in individuals who:

• Consume corticosteroid medications for asthma or COPD (Chronic Obstructive Pulmonary Disease), lupus, or gout
• Are infected with the HTLV-1 virus
• Have malignancies, such as leukemia and lymphoma
• Are transplant recipients

Severe infection (hyperinfection) can cause further damage to the intestinal wall, leading to bacterial infections in the body. Bleeding, malabsorption (intestinal disorders), and inflammation in the perineum (thin membrane on the abdomen) can occur. Larvae can also enter the central nervous system and cause meningitis. This condition requires immediate treatment.

Diagnosis

The doctor will ask about any symptoms experienced and conduct a physical examination to check for signs such as creeping eruptions on the soles of the feet, buttocks, and hands and any pain in the upper abdomen. However, the symptoms of Strongyloidiasis infection are not specific, so further tests may be necessary to establish a diagnosis. These tests include:

• Microscopic examination: Samples from feces or duodenal aspiration are examined under a microscope. Larvae are typically found in one sample, but repeated examinations can increase sensitivity. The recommended interval between examinations is 3 days.
• Complete blood count (CBC): An increase in eosinophil levels (a type of white blood cell) may be observed. However, this finding is not specific to Strongyloidiasis.
• Antigen test: Blood antigen testing can detect S. stercoralis. This test is performed if the doctor suspects a parasitic infection, but larvae are not found in fecal or duodenal samples.

In cases of hyperinfection, larvae may be found in various bodily fluids, including feces, sputum, respiratory tract mucus, urine, pleural cavity fluid (lungs), and cerebrospinal fluid (brain).

Management

The treatment of Strongyloidiasis involves using anti-parasitic medications such as ivermectin and albendazole. These medications effectively kill the worms in the small intestine. Both drugs require a doctor's prescription. If symptoms persist, a fecal examination should be repeated 2–4 weeks after completing the medication course to ensure the infection has been cleared. If larvae are still detected, retreatment is necessary. Further examinations of eosinophil levels and serology may also be required to confirm the successful resolution of the infection.

In cases of hyperinfection, patients with Strongyloidiasis may require prolonged treatment with both anti-parasitic and antibiotic medications.

Screening for Strongyloidiasis is recommended for individuals who:

• Are starting corticosteroid or other immunosuppressive drug therapy
• Have HTLV-1 infection
• Have blood malignancies, such as leukemia or lymphoma
• Have received or are planning to undergo organ transplantation
• Experience unexplained persistent eosinophilia
• Have a history of traveling to endemic areas

Complications

Continuous Strongyloidiasis can lead to the following complications:

• Malnutrition: Damage to the intestinal mucosa by S. stercoralis can hinder nutrient absorption, leading to malnutrition when the intestines cannot absorb nutrients from consumed food.
• Hyperinfection: This condition is characterized by a high number of larvae in specific parts of the body. Severe infection with S. stercoralis can occur, especially in individuals using immunosuppressive drugs or experiencing immunosuppression due to viruses.
• Disseminated infection: This is a continuation of hyperinfection, where larvae can be found throughout the body, spreading from the intestines to other organs and tissues.

Strongyloidiasis has a favorable outcome with proper management, and the worms can be completely eliminated. However, in some cases, treatment may need to be repeated to ensure eradication of the infection.

Prevention

The primary prevention methods for Strongyloidiasis include:

• Wearing footwear when walking on soil and avoiding contact with human feces. Good waste management practices, such as proper disposal of feces, are essential for prevention.
• Utilizing household toilet
• Practicing proper hygiene, such as washing hands before and after activities, minimizes the risk of parasite exposure.
• Avoiding direct contact with soil
• Refraining from using human feces as fertilizer
• Using gloves when handling waste or garbage to prevent contamination.
• Maintaining environmental cleanliness

When to see a doctor?

If you experience any of the symptoms listed above or suspect you have Strongyloidiasis, seeking medical attention promptly is important. Visit the nearest healthcare facility to undergo proper diagnosis and initiate treatment.