What are the Symptoms of Strongyloidiasis?
Strongyloidiasis is a parasitic infection caused by the roundworm Strongyloides stercoralis. While more common in tropical and subtropical areas with poor sanitation, it can occur in temperate climates as well. This infection has unique features that can make it a long-lasting health problem. Understanding its symptoms is key to recognizing and treating it.
Before detailing the symptoms, here's a brief overview of the infection:
- Initial Infection: Microscopic Strongyloides larvae in contaminated soil enter the body by burrowing directly through a person's skin. This often happens when walking barefoot or handling contaminated soil.
- Larval Migration: Once inside, larvae travel through the bloodstream to the lungs. They mature further, move up to the throat, and are swallowed. In the small intestine, they become adult female worms and lay eggs.
- Autoinfection: A distinctive trait of Strongyloides is autoinfection. Some larvae hatched in the intestine can mature and re-infect the person by burrowing through the intestinal wall or the skin around the anus, all without leaving the body. This allows the infection to persist for many years.
Digestive System Disturbances
Since adult Strongyloides worms reside in the small intestine, digestive problems are common symptoms. These can range from mild discomfort to severe issues affecting nutrition and daily life.
Abdominal Pain and Tenderness
Adult worms burrow into the lining of the small intestine, particularly the upper parts (duodenum and jejunum), causing irritation. The body's natural inflammatory response to these worms can lead to pain. This pain might feel like cramping, a dull ache, or even sharp pangs. The location and intensity can vary, sometimes being general or localized, and may come and go depending on the number of worms.
Diarrhea and/or Constipation
Strongyloides infection can disrupt normal bowel function. Inflammation may cause food and waste to pass too quickly, resulting in diarrhea (loose, watery stools) and poor absorption of water. Conversely, some individuals might experience constipation due to altered gut movement. Sometimes, these conditions can alternate, making bowel habits unpredictable.
Nausea and Vomiting
Irritation of the upper digestive tract by worms or larvae can trigger nausea and the urge to vomit. This is often a reflex as the body tries to expel the parasites. Persistent nausea and vomiting can lead to dehydration, electrolyte imbalances, and reduced nutrient intake, weakening the individual.
Bloating, Gas, and Malabsorption
Many people with strongyloidiasis report uncomfortable bloating and excessive gas. This can result from inflammation, an imbalance in gut bacteria, or problems with digestion. In chronic or heavy infections, ongoing damage to the intestinal lining can lead to malabsorption. This means the body struggles to absorb essential nutrients like fats, vitamins, and proteins, potentially causing unintentional weight loss, fatigue, and nutritional deficiencies, even with adequate food intake.
Skin Rashes and Respiratory Issues
The journey of Strongyloides larvae through the body can cause symptoms in the skin and respiratory system, often appearing before significant gut problems develop.
Skin Reactions
The first skin sign may be an itchy, red rash where larvae entered the skin, typically on the feet or hands. This is a local reaction to the invading larvae. Some people may also develop widespread itchy hives (urticaria) as a more general allergic response to the parasite. These rashes can be temporary or recurrent.
Larva Currens ("Racing Larva")
A very characteristic skin symptom is larva currens. This appears as rapidly moving, itchy, raised, linear, or snake-like tracks on the skin, often on the buttocks, groin, thighs, or abdomen. These tracks are formed by larvae migrating under the skin at several centimeters per hour, much faster than other similar larval migrations, making this symptom quite specific to Strongyloides infection. The intense itch associated with larva currens can be very distressing.
Respiratory Discomfort
As Strongyloides larvae travel from the bloodstream to the lungs, they can cause respiratory symptoms. Individuals might experience a dry cough, wheezing, or shortness of breath, sometimes with a low-grade fever or chest tightness. These symptoms arise as larvae pass through lung tissues, triggering inflammation. Severity varies from mild to more pronounced discomfort, sometimes mimicking asthma or bronchitis.
Potential for Worsening Lung Problems
While often temporary, these lung symptoms can be more serious if there's a high number of larvae or if the person has pre-existing lung conditions. In some instances, inflammation can cause patchy areas on chest X-rays, similar to pneumonia. These lung symptoms are a direct result of the parasite's migration.
The Silent Infection: Chronic and Asymptomatic Cases
A deceptive feature of strongyloidiasis is its ability to persist as a chronic, often symptom-free infection for many years, even a lifetime.
Decades of Quiet Persistence
Due to its autoinfection capability, Strongyloides can remain in the body for decades. In people with a healthy immune system, parasite numbers are usually kept low, causing a mild infection that doesn't provoke acute illness. This allows a person to carry the infection from childhood into adulthood unknowingly, a key reason it is often underdiagnosed.
Mild or Vague Symptoms
When chronic strongyloidiasis does cause symptoms, they are often mild, intermittent, or non-specific, easily mistaken for other common conditions. These might include vague abdominal discomfort, occasional diarrhea or constipation, fleeting itchy rashes, or a subtle, persistent cough. An unexplained increase in eosinophils (a type of white blood cell) in a blood test might be the only clue.
The Hidden Threat of Severe Disease
An asymptomatic or mildly symptomatic chronic infection carries a hidden risk. If the host's immune system weakens (due to corticosteroid treatment, other immunosuppressive drugs, certain viral infections like HTLV-1, or some cancers), the infection can escalate dramatically. This can lead to hyperinfection syndrome or disseminated strongyloidiasis, where larvae multiply uncontrollably and spread, causing severe, often fatal, illness.
When Strongyloidiasis Becomes Life-Threatening: Hyperinfection Syndrome
Chronic strongyloidiasis can turn dangerous if the host's immune system is significantly weakened. This can lead to hyperinfection syndrome, a severe emergency where Strongyloides larvae multiply uncontrollably.
Immune System Failure as a Trigger
A healthy immune system usually controls Strongyloides. However, if immunity is compromised (e.g., by corticosteroid therapy, HTLV-1 infection, organ transplantation, or cancers like lymphoma), this control is lost. The autoinfective cycle accelerates, leading to a massive increase in larval production and migration.
Overwhelming Larval Numbers
In hyperinfection syndrome, the number of larvae migrating through the body increases exponentially. They intensify their invasion of the gut and lungs, causing extensive damage. The body's systems become overwhelmed, leading to widespread inflammation and tissue injury. Symptoms become far more severe than in uncomplicated strongyloidiasis.
Severe Impact on Multiple Organs
The gastrointestinal system may suffer severe inflammation, ulcers, bleeding, and an inability to absorb nutrients, leading to severe malnutrition. In the lungs, massive larval migration can cause acute respiratory distress syndrome (ARDS) and severe pneumonia-like symptoms. Critically, migrating larvae can carry bacteria from the gut into the bloodstream and other body parts, frequently causing life-threatening bacterial infections like sepsis or meningitis.
Disseminated Strongyloidiasis: Widespread Invasion
In the most extreme cases, hyperinfection can progress to disseminated strongyloidiasis. Here, larvae spread beyond the gut and lungs to almost any organ, including the brain (causing meningitis or abscesses), liver, heart, and kidneys. This widespread parasitic invasion often results in multi-organ failure and has a very high risk of death if not diagnosed and treated urgently.
