bubble_chart Overview

Strongyloidiasis (Strongyloides stercoralis) is a facultative parasite with alternation of generations. Its free-living generation occurs in soil, while the parasitic generation develops within the human body. The life cycle is relatively complex, and the disease progression is prolonged. Clinical symptoms vary widely, ranging from asymptomatic cases to severe manifestations such as ulcerative inflammation of the small intestine and colon, which can even lead to death. The domestic infection rate of this parasite is approximately 10%.

bubble_chart Pathogen

(1) Free-living generation: Male worms measure approximately 0.7 × (0.04–0.05) mm, and female worms measure about 1.0 × (0.05 × 0.075) mm. The eggs resemble hookworm eggs, measuring about 70 μm × 40 μm. In warm and moist soil, the eggs hatch into rhabditiform larvae within a few hours. The rhabditiform larvae undergo several molts over 1–2 months Neijing and develop into free-living adults. The free-living generation can cycle multiple times. The rhabditiform larvae can also develop into filariform larvae after two molts, directly penetrating the skin to invade humans and adopt a

Chinese Taxillus Herb

lifestyle. (2)

Chinese Taxillus Herb

generation: After the infective larvae (filariform larvae) invade the human body, they enter the bloodstream, pass through the right heart to the lungs, penetrate the alveolar capillary walls, and migrate via the bronchi and pharynx to the digestive tract, where they mostly mature and settle in the

small intestine

. However, they can also

Chinese Taxillus Herb

in the

large intestine

and lungs, among other sites. It is generally believed that there are no male worms

Chinese Taxillus Herb

in the human body. Female worms measure about 2.2 mm × (0.03–0.075) mm. The pharynx is one-third or two-fifths of the body length, and the

vaginal orifice

is located in the posterior third of the body. Female worms often burrow into the intestinal

membrane

to lay eggs. The eggs are slightly smaller than those of the free-living generation and contain larvae, which hatch into rhabditiform larvae within hours. These larvae emerge from the intestinal

membrane

and are excreted in feces. These rhabditiform larvae can develop in two ways: 1. They molt directly in the external environment to become infective filariform larvae, which gather in the soil and penetrate the skin to invade humans, adopting a

Chinese Taxillus Herb

lifestyle. 2. The rhabditiform larvae excreted in feces do not develop into filariform larvae in the external environment but instead develop into free-living male and female adults. After mating and laying eggs, they hatch into rhabditiform larvae, which then develop into adults, lay eggs, and hatch more rhabditiform larvae, repeating the cycle multiple times in the external environment as free-living organisms. When environmental conditions change, the rhabditiform larvae of the free-living generation can develop into filariform larvae, penetrate the skin, and invade humans to adopt a

Chinese Taxillus Herb

lifestyle.

Additionally, during

Chinese Taxillus Herb

in humans, this parasite can also cause autoinfection. There are three main types of autoinfection: ① Direct internal autoinfection: After rhabditiform larvae hatch from eggs in the intestinal

membrane

, they directly invade the bloodstream and continue developing. ② Indirect internal autoinfection: Rhabditiform larvae emerge from the intestinal

membrane

and rapidly molt twice in the intestinal lumen to become filariform larvae, which then invade the bloodstream from the lower

small intestine

or colon

membrane

. ③ External autoinfection: Filariform larvae excreted in feces re-invade the human body through the perianal skin.

bubble_chart Pathological Changes

The pathogenic effects of Strongyloides stercoralis in grade I infection are relatively mild. However, since this parasite can cause autoinfection, grade III infection may lead to the death of the patient. Therefore, the pathogenic role of this parasite has gradually attracted attention. The pathological changes caused by the migration of the parasite in the human body or Chinese Taxillus Herb vary depending on the location.

(1) Perianal skin lesions: When larvae invade the skin around the anus, they can cause small bleeding spots, papules, and edema, which may be accompanied by secondary bacterial infections if scratched. Additionally, migrating linear or band-like urticaria often appears on the perianal skin and can persist for several weeks. These lesions may also occur in areas such as the groin and buttocks.

(2) Intestinal lesions: The intestinal lesions caused by Strongyloides stercoralis can be classified into three types: grade I, grade II, and grade III. The main feature of grade I is catarrhal enteritis, with congestion of the intestinal mucosa, small bleeding spots, and ulcers. Microscopically, eosinophil and monocyte infiltration can be observed, and Strongyloides stercoralis is present in the intestinal crypts. Grade II is characterized by edematous enteritis, with thickening and edema of the intestinal wall and reduced mucosal folds. Microscopically, enlarged intestinal villi, mucosal atrophy, and submucosal edema can be seen, and the parasite can be found in all layers of the intestinal wall. Severe cases may exhibit hemorrhage, erosion, ulcers, swollen lymphoid follicles, and even intestinal perforation. Due to edema and fibrosis, the intestinal wall becomes thickened and stiff, with partial rigidity, mucosal atrophy, and multiple ulcers ranging from 2 to 50 mm in diameter. Microscopically, fibrosis and submucosal edema, atrophy of the muscle layer, and the presence of the parasite throughout the thickened intestinal wall can be observed.

(3) Other lesions: When the larvae of this parasite migrate in the lungs, they can cause congestion and hemorrhage of pulmonary capillaries, shedding of bronchiolar epithelial cells, and inflammatory exudates containing larvae. If the larvae remain in the lungs or intestines for too long and develop into adults, most will form millet-sized lung abscesses. When filariform larvae migrate in the body, they may also invade other organs, such as the endocardium, liver, ovaries, mesenteric lymph nodes, and brain, leading to granuloma formation.

bubble_chart Clinical Manifestations

In most cases, this disease presents no obvious clinical symptoms. However, due to the parasite's ability to cause repeated autoinfection, when the host's immunity is compromised—such as during illness, malnutrition, immune deficiency, or treatment with hormones or other immunosuppressive agents—grade III autoinfection may recur frequently, leading to severe symptoms or even death.

(1) No clinical symptoms on perianal skin: When filariform larvae invade the perianal skin, local symptoms such as edema, stabbing pain, and cutaneous pruritus may appear, often accompanied by linear or band-like urticaria. Since the larvae migrate rapidly through the skin, the resulting urticaria spreads quickly. One reported case documented urticaria spreading at a rate of 10–12 cm per hour. The appearance and rapid spread of urticaria around the perianal skin are key diagnostic indicators of Strongyloides stercoralis larvae migrating through the skin.

(2) Intestinal symptoms and signs: The intestinal manifestations of Strongyloides stercoralis infection primarily include chronic diarrhea, frequent loose stools, watery or mucoid bloody stools, and tenesmus. Other symptoms include abdominal pain, typically localized to the right upper quadrant, and occasionally constipation. In grade III infections, nausea, vomiting, paralytic ileus, abdominal distension and fullness, electrolyte imbalances, dehydration, and even intestinal perforation, systemic failure, or death may occur. Some acute cases may produce foul-smelling, frothy white stools or severe steatorrhea, possibly due to malabsorption or rupture of intestinal lymphatic vessels, allowing fat to enter the intestinal lumen.

(3) Other symptoms and signs: When the larvae migrate through the lungs, they can cause allergic pneumonia and asthma, presenting with grade I fever, cough, and sputum production. Chest X-rays may reveal localized or diffuse inflammatory shadows. If larvae remain in the lungs and mature into adults, their offspring may invade the pleural cavity, causing pleuritis. Additionally, metabolic and decomposition products of the parasites can induce systemic toxic symptoms such as fever, anemia, and neurological manifestations like dysphoria and insomnia. Acute infections may trigger eosinophilia, often reaching 15–85%.

bubble_chart Diagnosis

The diagnosis of this disease primarily relies on the detection of rhabditiform or filariform larvae in the stool. However, conventional stool smear methods may sometimes fail to detect the larvae, in which case the Baermann technique can be used to directly isolate the larvae from the stool. Some have applied a modified formalin-ether centrifugation method with good results. If both rhabditiform and filariform larvae are found in fresh stool samples within 24 hours, it can be considered indicative of autoinfection. Occasionally, eggs may also be detected in the stool of patients with diarrhea. If repeated stool examinations yield negative results, gastric fluid, duodenal fluid, or sputum should be examined in conjunction with clinical symptoms. If pathogens are still not detected after repeated testing, immunological tests may be considered to aid in diagnosis. Japanese researchers have used enzyme-linked immunosorbent assay (ELISA) to detect serum antibodies in patients, achieving a positive rate of 94.4%, while all control cases were negative. This method is considered to have satisfactory sensitivity and specificity for diagnosing this disease.

bubble_chart Treatment Measures

For confirmed cases, immediate deworming treatment should be administered, ensuring smooth bowel movements and maintaining cleanliness around the anus to prevent self-infection. The most effective treatment is thiabendazole, with a dose of 25mg/kg, taken orally twice daily for 2 to 4 days, achieving a cure rate of 92-94%. Common side effects of this medication include dizziness and gastrointestinal symptoms. For patients with liver or kidney dysfunction, Chinese Gentian Violet is recommended at a dose of 0.2-0.4g, divided into three oral doses after meals for seven days. Other medications such as mebendazole, albendazole, and levamisole also show some efficacy, with cure rates ranging from 64-75%. Asymptomatic or mildly symptomatic individuals infected with this parasite generally have a good prognosis after successful deworming treatment. However, due to the risk of self-infection, recurrence is common post-treatment. Patients with grade III infections or those with extraintestinal ectopic Chinese Taxillus Herb have a poor prognosis.

bubble_chart Prevention

The prevention principle of this disease involves paying attention to personal protection and avoiding autoinfection, especially before the clinical use of hormonal drugs or immunosuppressants. Routine examination for Strongyloides stercoralis should be conducted. If infection with this parasite is detected, thorough treatment should be administered to prevent the occurrence of grade III autoinfection.

bubble_chart Differentiation

The clinical manifestations of this disease are complex, the course is long, and misdiagnosis is prone to occur. Therefore, it should be differentiated from other diseases. When the chief complaint is bloody or watery stools, it should be distinguished from bacterial dysentery, amoebic dysentery, and ulcerative colitis. When the chief complaint is abdominal pain, it should be differentiated from gastric and duodenal ulcers, as well as acute cholecystitis.