Strongyloidiasis is an invasion of round helminths – intestinal acne, occurring with allergic and gastrointestinal syndromes. The manifest course of strongyloidiasis is accompanied by itchy skin rashes, cough with an asthmatic component, nausea, vomiting, diarrhea, myalgia, arthralgia, hepatosplenomegaly, jaundice of the skin and sclera. The diagnosis is confirmed by the detection of worm larvae in feces or duodenal contents, as well as antibodies to helminth in the blood. Strongyloidiasis is treated with anthelmintic drugs (tiabendazole, ivermectin).
Strongyloidiasis is an intestinal nematode characterized by a predominant lesion of the digestive and hepatobiliary systems, as well as allergic reactions from the skin and respiratory organs. For the first time, strongyloidiasis was described in the last quarter of the XIX century. based on observations of soldiers who returned from Vietnam and suffered from persistent diarrhea. Then helminthiasis was called “Cochin diarrhea”. The incidence of strongyloidiasis is mainly characteristic of the tropical and subtropical zone, where the invasion of the population by intestinal acne reaches 30-40%. In USA, strongyloidiasis is detected with a frequency of 0.2–2%. Currently, interest in strongyloidiasis is due to its attribution to HIV-associated parasitoses.
Helminth invasion is caused by a representative of the round parasitic worms Strongyloides stercoralis – intestinal eel. The development of the helminth proceeds with the change of the parasitic (filiform) and free-living (rhabditic) generation. Adult eels are small filamentous nematodes 0.7-2.2 mm long, 0.03-0.07 mm wide, living in the crypts of the duodenum 12 (with massive invasion – in the pyloric part of the stomach and the entire small intestine). At the head end of the helminths there is a mouth opening. Intestinal acne – bisexual helminths; after fertilization, the female lays up to 50 eggs in the intestine per day, from which non-invasive (rhabditic) larvae emerge. Together with the feces, the larvae enter the external environment – the further development of the causative agent of strongyloidiasis occurs in the soil.
After molting, the larvae turn into free-living mature individuals capable of laying eggs in the soil. Some of the rhabditoid larvae emerging from the eggs differentiate into sexually mature worms, the other turns into filariform larvae capable of invasion. The penetration of intestinal eel larvae into the host body occurs mainly by percutaneous route (through the skin in contact with the soil), infection with strongyloidiasis by alimentary route is also possible (when eating products and water infested by larvae). In some cases, rhabditoid larvae turn into filariform larvae directly in the human intestine, thus realizing the mechanism of autoinvasion in strongyloidiasis. This situation is usually observed in people with impaired immune system function, as well as those suffering from constipation. The increased incidence of strongyloidiasis is noted among patients with gastrointestinal diseases, HIV infection, tuberculosis. Nosocomial outbreaks of strongyloidiasis in psychiatric hospitals are described.
Having penetrated into the human body through the skin or mucous membranes of the gastrointestinal tract, the larvae enter the bloodstream, the small circle of blood circulation, and then into the bronchioles and bronchi. When coughing, along with sputum, the larvae enter the pharynx, from where, when swallowing bronchial secretions, they penetrate into the digestive tract. Here they transform into mature individuals and lay eggs. In the migration stage, which lasts about 1 month, sensitization of the body by the products of vital activity and decay of larvae develops, which finds clinical expression in the occurrence of allergic reactions. In organs where intestinal acne larvae parasitize, an inflammatory reaction occurs, eosinophilic infiltration, granulomas, abscesses. Erosions, ulcerative lesions, and hemorrhages form in the small intestine. Adults parasitize in the host body for several months, but with autoinvasion, strongyloidiasis can last up to 20-30 years. With immunodeficiency, generalization of infection with migration of larvae to the brain, myocardium, liver, attachment of secondary bacterial flora with the development of fatal outcomes is possible.
According to the severity of clinical symptoms, the course of strongyloidiasis can be asymptomatic and manifest; according to severity – mild, moderate or severe. Asymptomatic forms are noted in people living in endemic foci. In the development of manifest strongyloidiasis, there are early (migratory) and late (chronic) phases.
The early phase of strongyloidiasis occurs with a predominance of allergic reactions: itchy skin rashes like urticaria, paroxysmal cough, hypereosinophilia. The rash is blisters of a pinkish-reddish color, usually localized on the abdomen, thighs, buttocks, back, chest. When combing the elements, the area of the skin lesion increases. The rash disappears without a trace after 2-3 days, but periodically returns again. It is possible to develop asthmatic bronchitis, pneumonia, acute allergic myocarditis. When radiography of the lungs reveals volatile infiltrates. In the early period, patients with strongyloidiasis are worried about fever of the wrong type, arthralgia and muscle pain, fatigue, irritability, headache. Approximately 2-3 weeks after the onset of an allergic symptom complex, dyspeptic disorders develop, characterized by epigastric pain, nausea, vomiting, diarrhea with tenesmus. In some cases, there is an increase in the liver and spleen, the appearance of jaundice of the skin and sclera.
In the late phase, depending on the prevailing syndrome, strongyloidiasis can occur in duodenal-cholelithiasis, gastrointestinal, neuro-allergic and mixed forms. Duodeno-cholelithiasis is accompanied by moderate pain syndrome in the right hypochondrium, bitterness in the mouth, loss of appetite, periodic nausea. According to cholecystography, dyskinesia of the gallbladder is established. In the gastrointestinal form, dyspeptic disorders are leading in the clinic of strongyloidiasis: prolonged diarrhea, sometimes alternating with constipation, abdominal pain. Against this background, patients may strongyloidiasis hypoacid gastritis, enteritis, proctosigmoiditis, duodenal ulcer, gastrointestinal bleeding. Signs of the neuro-allergic form of strongyloidiasis are persistent itchy rashes, astheno-neurotic syndrome, sweating, insomnia, increased irritability. The listed variants of strongyloidiasis rarely occur in isolation, their symptoms usually combine with each other, causing the development of a mixed form of helminthic invasion. In patients with immune suppression, the course of strongyloidiasis can be complicated by encephalitis, brain abscess, myocarditis, hepatitis, pyelonephritis, keratitis, conjunctivitis.
Diagnosis and treatment
Regarding certain clinical symptoms, patients with strongyloidiasis may unsuccessfully be treated by an allergist, dermatologist, gastroenterologist. The main signs that make it possible to think about helminthic invasion are a combination of urticaria, diarrhea, high blood eosinophilia and the lack of effect from the symptomatic treatment. Epidanamnesis data have a certain diagnostic value (being in foci of strongyloidiasis, working with the earth, suppression of immunity, etc.).
Laboratory diagnostics of strongyloidiasis is based on the detection of parasite larvae in feces, sputum or duodenal contents obtained by probing the duodenum 12. In chronic invasion, serological tests (IFR, ELISA), which detect the presence of antibodies to the parasite, have the greatest sensitivity. In the early period, in patients with strongyloidiasis, it is necessary to exclude drug and food allergies; in the late period, dysentery.
Patients with strongyloidiasis are hospitalized in infectious diseases clinics. Specific anthelmintic therapy is carried out with drugs tiabendazole or ivermectin; less often – albendazole, mebendazole. In parallel, desensitizing agents are prescribed, enzyme replacement therapy is carried out. Repeated tests are taken after two weeks and then monthly for 3 months.
Prognosis and prevention
In most cases, deworming leads to a cure for strongyloidiasis, however, patients with a chronic form require long-term (within 1 year) rehabilitation in order to restore gastrointestinal function. With the development of organ complications, the mortality rate reaches 60-85%. The main preventive directions include the identification and treatment of infected persons, protection of soil from fecal contamination, sanitary improvement of settlements. It should be remembered that it is unacceptable to fertilize the soil in gardens and vegetable gardens with untreated feces; the use of unwashed vegetables, fruits, herbs, unboiled water; excavation work without protective gloves. The key to mass prevention is to raise awareness of the population about possible ways of infection with strongyloidiasis and other intestinal helminthiasis.