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PubMed1991

A modified agar plate method for detection of Strongyloides stercoralis.

The agar plate method is a new technique with high detection rates for coprological diagnosis of human strongyloidiasis. This report details modifications of the technique and establishes a standardized procedure. We recommend that all plates should be carefully observed using a microscope because macroscopic observation can lead to false negative results. It is also advisable to pour formalin solution directly into microscopically positive dishes to collect worms by sedimentation. This procedure enables one to observe worms otherwise hidden. Sealing dishes with adhesive tape prevents larvae from crawling out of the dishes, eliminating any possibility in the reduction of detection rates, and greatly improves the safety conditions for the technician performing the procedure. We consider the agar plate method to be superior to the filter paper method in detecting Strongyloides, and we believe that it will eventually become the technique of choice.

Animals↗
PubMed1992

Strongyloides stercoralis infection in IgA-deficient dogs.

Two litters of eight-week-old, IgA-deficient pups, each including one normal littermate control, were infected with 5,000 infective third-stage Strongyloides stercoralis larvae per pup. No significant differences between the dogs deficient in serum and mucosal IgA and the normal control dogs were observed in any of the parasitologic parameters measured during the course of infection. The time required to reach patency, the maximum number of larvae shed in the feces, the number of days postinfection at which larval shedding was at its maximum, and the time required to eliminate shedding were similar in the two groups. Once larval shedding ceased, there was no recrudescence, even though serum and fecal IgA were absent or low throughout the seven-month course of the investigation. All dogs remained asymptomatic, with complete blood counts and clinical chemistries within normal ranges. In addition, serum IgM and IgG levels were within the normal range for both groups of infected dogs. All dogs from which necropsy samples were obtained harbored low numbers of adult female worms, some of which were barren. An IgA deficiency apparently does not affect the course or severity of S. stercoralis infection in the dog.

Animals↗
PubMed1994

Prospective evaluation of enzyme-linked immunosorbent assay and immunoblot methods for the diagnosis of endemic Strongyloides stercoralis infection.

Recently described enzyme-linked immunosorbent assay (ELISA) and immunoblot methods for the detection of serum IgG against Strongyloides stercoralis larval antigens were prospectively evaluated for the diagnosis of endemic strongyloidiasis. A modification of the ELISA involved preincubation of sera with Onchocerca gutturosa phosphate-buffered saline-soluble extract to remove cross-reactivity with other helminths. The sensitivity of the ELISA increased from 80% to 85% following preincubation. Similarly, there was an increase in specificity from 94% to 97%. The IgG recognition of 41-, 31-, and 28-kD filariform larval components showed sensitivities of 100%, 85%, and 65%, respectively. Both the ELISA following incubation of sera with O. gutturosa extract and serum IgG reactivity to a 41-kD larval component using immunoblotting are sensitive and specific techniques for diagnosing endemic strongyloidiasis.

Animals↗
PubMed1995

Gamma camera scintigraphy for direct visualization of larval migration in Strongyloides stercoralis-infected dogs.

Gamma camera scintigraphy of dogs infected with radiolabeled third-stage larvae of Strongyloides stercoralis was successful for visualizing larval migration in a live host. Ten-day-old pups were infected subcutaneously in a lateral inguinal site with 100,000 75Se-selenomethionine-labeled third-stage S. stercoralis and imaged serially using a clinical gamma camera during the prepatent period. Radioactivity corresponding to the larval inoculum was visualized at the infection site immediately after injection. Radioactivity spread diffusely, corresponding to radial dispersal of larvae from the infection site. The majority of the radioactivity concentrated over or through the abdomen from 48 to 144 hr after infection. Larvae arrived in the small intestine in numbers adequate for visualization beginning at 114 hr after infection. At no time was there concentration of radioactivity associated with the lungs of an infected pup. A control pup injected only with 75Se-selenomethionine showed uniform activity diffusely throughout the entire body at all times. We concluded that the majority of larvae moved to the gut by means other than the pulmonary route.

Abdomen↗
PubMed1996

Short report: long-term serum antibody isotype responses to Strongyloides stercoralis filariform antigens in eight patients treated with ivermectin.

The enzyme-linked immunosorbant assay was used to investigate long-term changes in serum immunoglobulin G1 (IgG1), IgG4, IgE, and IgA against Strongyloides stercoralis phosphate-buffered saline-soluble filariform larval antigens in eight Jamaican patients treated with ivermectin. Patients were followed for periods of between 170 and 542 days. Based on repeated formalin-ether concentration and agar plate culture, all patients were found to be uninfected up to 18 months following chemotherapy. Generally, all antibody isotype levels decreased following treatment, although there was considerable heterogeneity among patients. In a single patient with hyperinfection, the decrease in IgG4 was marginal and may represent a treatment failure. Reduction in serum antibody isotype responses to S. stercoralis following treatment may be used to assess the effectiveness of ivermectin in treating endemic strongyloidiasis.

Animals↗
PubMed1996

A comparative trial of a single-dose ivermectin versus three days of albendazole for treatment of Strongyloides stercoralis and other soil-transmitted helminth infections in children.

A randomized trial carried out in rural Zanzibar comparing a single dose of 200 micrograms/kg of ivermectin and 400 mg/day for three days of albendazole for treatment of strongyloidiasis and other intestinal nematodes is described. In 301 children with Strongyloides stercoralis infection, treatment with ivermectin or albendazole resulted in cure rates of 83% and 45%, respectively. While both drugs were very effective against Ascaris lumbricoides, Trichuris trichiura was cured only in 11% (ivermectin) and 43% (albendazole) of the subjects, although the mean eggload was reduced by 59% and 92%, respectively. Ivermectin was ineffective against hookworms, while albendazole resulted in a cure rate of 98%. No severe side effects were recorded and mild side effects were of transient nature for both treatments. Therefore, ivermectin provides a safe and a highly effective single dose treatment for S. stercoralis and A. lumbricoides, while it is not an alternative for the treatment of T. trichiura and hookworm infections.

Adolescent↗
PubMed1996

Strongyloides stercoralis: maintenance of exceedingly chronic infections.

Two hypotheses were tested to identify the mechanism(s) by which chronic Strongyloides stercoralis infections are maintained in experimental dogs as a model to explain delayed onset recrudescence in humans. Investigations tested the hypotheses that chronic infections result from 1) periodic reactivation of third-stage larvae from a reservoir of dormant parasites outside the gastrointestinal tract or 2) the periodic rejuvenation of postreproductive female worms remaining from a previous infection, lodged in the mucosal crypts. Populations of parenteral larvae survived in mature experimentally infected female dogs for 66 days; individual worms survived for 88 days, but there was no evidence that these larvae re-established patent, adult worm infections. Late in these infections, female worms were present in greater than predicted numbers with no evidence that autoinfection had occurred, suggesting that some postreproductive worms were long-lived. In separate trials, long-lived spent females were once again capable of producing viable larvae when the host was treated with corticosteroids.

Animals↗
PubMed1997

Chronicity in Strongyloides stercoralis infections: dichotomy of the protective immune response to infective and autoinfective larvae in a mouse model.

Strongyloidiasis is an intestinal disease that can last for decades due to the occurrence of autoinfective larvae (L3a) in an infected person, which contribute to the maintenance of the population of adult worms in the intestine. The goal of the present study was to determine if L3a are susceptible to the protective immunity that targets the infective stage of the worm, the third-stage larvae (L3). Mice immunized and challenged with Strongyloides stercoralis L3 kill more than 90% of challenge larvae contained within diffusion chambers. The L3 do not remain antigenically static in mice, however, but undergo some degree of antigenic change before they are killed, becoming host-activated larvae (L3+). The L3/L3+ are killed in this model system by the combined effects of both parasite-specific IgM and eosinophils. Mice immunized with L3 were able to kill L3/L3+, but did not kill L3a, in challenge infections. Eosinophils were, however, present in diffusion chambers containing L3a, and IgM bound to the surface of L3a. We hypothesized that differential IgM recognition of soluble L3a, L3, and L3+ antigens is the reason why the immune response generated against L3 could not kill L3a. Many common antigens on L3, L3+, and L3a were recognized by serum from mice immunized with L3, as determined by immunoblotting. However, several unique L3, L3+, and L3a antigens were also recognized by immune serum, thus indicating that antigen recognition with IgM antibodies is different between the L3, L3+, and L3a stages. This difference in antigen recognition could explain why L3a are able to evade the immune response that targets L3/L3+ in chronically infected hosts.

Animals↗
PubMed1999

Fluctuations of larval excretion in Strongyloides stercoralis infection.

Follow-up stool examinations were carried out on two groups of the subjects who were screened negative (group 1) or positive (group 2) for Strongyloides stercoralis by the agar plate culture. This technique could detect S. stercoralis larvae in 87.5-96.4% of the subjects in group 2 and 0-5.9% of the subjects in group 1 on various days of the eight-week and four-week follow-up periods, respectively. The detection rate on each day of examination was not statistically different from that on the first day in both groups. Quantitative measurement of S. stercoralis larvae excreted in the feces of the subjects in group 2 by the standard direct smear method of Beaver and others revealed slight to marked fluctuations of the larval output in individual subjects. From the results of both stool examination methods, it could be implied that 52% of S. stercoralis-infected individuals had low-level infection.

Adolescent↗
PubMed2001

Skin test antigens for immediate hypersensitivity prepared from infective larvae of Strongyloides stercoralis.

More rapid and simplified diagnostic procedures are needed for the diagnosis of strongyloidiasis. One approach is the use of an immediate hypersensitivity skin test that would reliably identify infected people. Accordingly, somatic and excretion/secretion (E/S) antigens were prepared from filariform larvae of Strongyloides stercoralis and were treated to remove possible adventitious agents. By use of a quantitative method for measurement of skin reactions, several preparations of the 2 antigens were tested in uninfected controls and in various groups of patients. Doses of 0.35 microg of E/S and 4 microg of somatic antigens elicited positive skin tests in 82-100% of infected people, depending on clinical status. A lower frequency of positive skin tests was found in strongyloidiasis patients also infected with human T-cell lymphotropic virus type 1. Cross-reactions, especially to somatic antigens, were frequently found in patients with filarial infections. Despite these limitations and the need for further study of specificity, these results provide a basis for future development of a diagnostic skin test antigen for strongyloidiasis.

Animals↗
PubMed2006

Histopathology of gastric and duodenal Strongyloides stercoralis locations in fifteen immunocompromised subjects.

CONTEXT: Strongyloidiasis is a worldwide parasitic infection affecting approximately 75 million people. In Italy, it was more prevalent in the past among rural populations of irrigated areas. OBJECTIVE: To determine the histopathologic alterations of the gastric and duodenal mucosa associated with the presence of Strongyloides stercoralis parasites. DESIGN: Fifteen cases of strongyloidiasis were observed in immunocompromised patients during a recent 6-year period in Italy. S. stercoralis was found histologically in gastric biopsies (10 cases), in a gastrectomy (1 case), and in duodenal biopsies (9 cases). In 5 cases the parasite was present both in gastric and duodenal biopsies. Four patients were affected by lymphoma, 2 by multiple myeloma, 2 by gastric carcinoma, 1 by chronic myeloid leukemia, 1 by sideroblastic anemia, 1 by colorectal adenocarcinoma, 1 by chronic idiopathic myelofibrosis, 1 by chronic gastritis, 1 by gastric ulcers, and 1 by rheumatoid arthritis in corticosteroid therapy. No patient was affected by human immunodeficiency virus infection. Strongyloidiasis was not clinically diagnosed. RESULTS: Histologic examination revealed several sections of S. stercoralis larvae, many eggs, and some adult forms. All the parasites were located in the gastric and/or the duodenal crypts. Eosinophils infiltrating into the lamina propria were found in all cases; their intensity was correlated with the intensity of the infection. CONCLUSIONS: Histologic diagnosis of strongyloidiasis must be taken into consideration when examining both gastric and duodenal biopsies in immunocompromised patients, to avoid the development of an overwhelming infection of the parasite, which is dangerous for the life of the patient.

Aged↗
PubMed1999

Hyperinfective strongyloidiasis: Strongyloides stercoralis undergoes an autoinfective burst in neonatal gerbils.

One of the unusual aspect of the life cycle of Strongyloides stercoralis is the occurrence of autoinfective third-stage larvae (L3a). These are the causative agents of severe hyperinfective strongyloidiasis. When 6-wk-old gerbils are infected with 1,000 infective third-stage larvae (L3i), no L3a are seen during the course of the infection. However, in neonatal gerbils (1-13 days of age) infected with 1,000 L3i, a burst of autoinfection takes place between 15 and 30 days postinfection (PI). Only occasional L3a can be found in neonatally infected gerbils after 4 wk PI. This autoinfective burst is not seen in neonatal gerbils infected with 200 L3i.

Animals↗
PubMedDate not supplied

[Role of hypocorticosteronemy in the self cure mechanism in rats with Strongyloides ratti parasites (author's transl)].

Repeated injections of corticosterone acetate, physiological hormone of the Rat, in rats carrying Strongyloides ratti, oppose the deparasiting which normally takes place spontaneously. The secretion induced by this hormone by impregnating the organism through the corticotropic factor administered in the form of tetracosactide-zinc, achieves the same result. During all these treatments, an important hypercorticosteronemy is established. Stopping the injections is quickly followed by the worms-being rejected and the corticosteronemy returning to normal. The relations between the corticosteronemy and the parasitism are analysed and lead to the conclusion that the parasite induces an aspecific hypocorticosteronemiant reaction which, through its aspecific and specific repercussions, participates in the self-cure phenomenon.

Animals↗
PubMed1999

Strongyloides ratti: migration study of third-stage larvae in rats by whole-body autoradiography after 35S-methionine labeling.

In order to clarify the migration pathway of Strongyloides ratti, Wistar rats were given 5,000 35S-labeled infective larvae subcutaneously and killed at 10, 15, 20, 25, 30, 40, and 50 hr postinfection. Prior to inoculation, the specific radioactivity level was assessed in the labeled larvae using a scintillation counter. The frozen rat specimens were sectioned at 50 microm, and the sections were freeze-dried and mounted on X-ray film in darkness. The labeled larvae appeared as dark spots on the film after 14 days of exposure. The infected larvae remained at the inoculated site (lower abdomen) until 10 hr after infection. Some larvae were found in the head portion, whereas others existed sporadically in the skin, liver, and lungs at 15 hr. After 20 and 25 hr, the majority of larvae had accumulated in the head portion. Many larvae appeared in the cranial and nasal cavities; however, no larvae were found in any other organs or tissues. At 30 hr, most larvae had begun to accumulate in the ethmoid region again. At 40 and 50 hr, some larvae were recognized in the ethmoid region, and most had already reached the small intestine. This suggests that the larvae directly move to the nasofrontal portion through the subcutis, rather than migrating to the head through either the viscera, ascending vessels, or the foramen occipital magnum.

Animals↗
PubMed1999

Pigmented nails and Strongyloides stercoralis infestation causing clinical worsening in a patient treated for immunoproliferative small intestinal disease: two unusual observations.

Immunoproliferative small intestinal disease (IPSID) is commonly reported from developing countries with poor socioeconomic conditions, hygiene, and high frequency of gastrointestinal infections and infestations. The disease requires anti-malignant chemotherapy in lymphomatous stage. Reported here is a 20-year old man with IPSID lymphoma who responded to anti-malignant chemotherapy initially, but later deteriorated due to Strongyloides stercoralis infestation, which was treated successfully with mebendazole. Importance of an early recognition and adequate treatment for gastrointestinal infections and infestations before anti-malignant chemotherapy for this disease is highlighted considering the occurrence of this disease in the developing world. The patient developed alternate brown black and white lines in the finger nails after combination chemotherapy, which has not been reported earlier in this disease; the nail changes disappeared 6 months after the withdrawal of doxorubicin suggesting this drug as the cause for such nail changes during anti-malignant combination chemotherapy.

Adult↗
PubMed2000

Strongyloides ratti: chemotactic responses of third-stage larvae to selected serum proteins and albumins.

Experiments were carried out in vitro to investigate whether the sera of several animals as well as albumins and peptides might act as attractants for larvae of Strongyloides ratti. Samples of sera from several mammal species were dialysed and the aliquots were further centrifuged using ultrafiltration cartridges to remove any remaining small molecules. Additional test substances included commercially obtained ovalbumin, rat and bovine serum albumins, polypeptides such as peptone, tryptone and tryptose, amino nitrogens, monosaccharides, and reduced glutathione (triaminopeptide). Larvae were strongly attracted to the dialysed mammalian sera, which mainly consisted of serum albumin and globulins. Ov- and serum albumins, and polypeptides also acted as attractants. On the other hand, reduced glutathione, 16 kinds of amino acids and four kinds of monosaccharides did not attract this nematode.

Animals↗