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PubMed1990

Strongyloides stercoralis associated with a bleeding gastric ulcer.

Infection with the helminthic parasite, Strongyloides stercoralis, is usually acquired by skin invasion (or occasionally via ingestion of larvae). After transformation to the adult form, the parasite preferentially localises in the small intestine, especially in the duodenal and jejunal part. A remarkable feature of Strongyloides is its property of endogenous reinfection. In the case of an immunocompromised host a massive infection, called hyperinfections Strongyloides, may occur. Numerous gastrointestinal complications of strongyloides infections, sometimes with a lethal outcome, have been reported. The intestinal manifestations are usually limited to the small bowel, and rarely involve the stomach. We report a patient with complicated strongyloides infection of the stomach.

Aged↗

PubMed2006

Strongyloides stercoralis infestation in a patient with severe ulcerative colitis.

Asymptomatic infestation with Strongyloides stercoralis, common in the tropics, may result in potentially fatal hyperinfection during treatment with immunosuppressive drugs used to treat patients with severe ulcerative colitis (UC). Hence, importance of early recognition and treatment of this nematode in patients with UC before starting immunosuppressive drugs can not be overemphasized. We report a 23-yrs old man with UC who presented with acute severe attack. Since his UC did not respond to intravenous hydrocortisone over 6 days, oral cyclosporine was started on 7th day after repeating stool microscopy, which revealed larvae of Strongyloides stercoralis. Duodenal aspirate also confirmed presence of multiple larvae. He responded to treatment for Strongyloides stercoralis , continuation of hydrocortisone and cyclosporine. Importance of early diagnosis of infestation with Strongyloides stercoralis while on treatment with immunosuppressive drugs for severe UC is emphasized. Difficulties in diagnosis and management of Strongyloides stercoralis infestation in patients with UC are discussed.

Animals↗

PubMedDate not supplied

Experimental infection of human subject with Strongyloides species.

Because of excellent and readily available animal models of infection with Strongyloides species, much of the basic biology of the parasite was understood by the early 1930s. Only selected issues of major physiologic importance were left to be addressed by intentional human infections. Concern about the strongyloides hyperinfection syndrome and the parasite's characteristic refractoriness to drug therapy led investigators of experimental human infections to act as subjects. This article reviews studies that describe experimental human infection with Strongyloides stercoralis and Strongyloides fülleborni as well as other Strongyloides species. These studies address two main issues: the clinical manifestations associated with the prepatent and early patent phases of infection, and the development of immunity to reinfection in individuals previously infected. The possible conclusions from these studies are discussed in the context of the current understanding of natural human and experimental animal infections.

Animals↗

PubMedDate not supplied

Characterization of a recombinant immunodiagnostic antigen (NIE) from Strongyloides stercoralis L3-stage larvae.

Due to the process of internal autoinfection, even chronic asymptomatic infections with Strongyloides stercoralis have the potential to become severe disseminated disease with fatal outcome. Intermittent and scanty larval excretion makes parasitologic diagnosis difficult. Serodiagnosis is helpful, but antigen preparation from infective larvae requires access to patients or immunosuppressed experimental animals. For these reasons, attention has turned to recombinant antigens for immunodiagnosis. A 31-kDa candidate antigen (NIE) derived from an L3 cDNA library is described in this report. Multiple alignment of the deduced amino acid sequence of NIE showed approximately 12-18% identity with various other organisms, including 17.9% of Asp1 of Ancylostoma caninum, 12.6% of Hemonchus contortus, and 17.6% of insect venom allergen 5 of yellow jacket. By ELISA, antibodies to the purified recombinant NIE antigen were demonstrated in 87.5% of 48 sera from strongyloides-infected patients and in only 6.5% of sera from presumed normal controls. Immunoreactivity of purified NIE antigen with parasite-specific IgE from sera of strongyloides-infected patients indicated its potential use as an immediate sensitivity skin test antigen. This application of the NIE antigen was supported by its capacity to trigger release of histamine upon in vitro exposure to blood from strongyloides-infected patients and its failure to produce histamine release from blood of normal controls.

Amino Acid Sequence↗

PubMed1980

The migration of Strongyloides papillosus in rabbits following infection by the oral and subcutaneous routes.

For the first 66 hours after the subcutaneous injection of rabbits with the infective larvae of Strongyloides papillosus, larvae spread gradually from the injection site to other parts of the body musculature. Their number and distribution suggests that they do so by the direct penetration of the tissues as the majority remain close to the site of injection. By 90 hours, however, the appearance of larvae in the lungs, trachea and oesophagus suggests that migration is taking place within the circulation. Although some 90% of the total worms recovered were already established in the intestine by 8 days post-infection, significant numbers of larvae continued to be present in the muscles at 14 and 21 days. Even by 35 days the muscles of 1 of 2 rabbits still contained 43 larvae. This prolonged presence of Strongyloides papillosus in the muscle of rabbits uniformly at the early fourth stage may be analogous to the arrested development of other nematodes. While there is evidence to suggest that immunity is a major factor in the aetiology of arrested development in Strongyloides ransomi, it is an unimportant factor in the case of Strongyloides papillosus in rabbits.

Animals↗

PubMed1979

Strongyloides stercoralis infection and small intestinal lymphoma.

A West Indian man who was infected with Strongyloides stercoralis developed small intestinal obstruction. Treatment with thiabendazole did not relieve the obstruction which was found at laparotomy to be due to a poorly differentiated small intestinal lymphoma. There was no blood eosinophilia or accumulation of eosinopohils in the sites of infection. There was no reaction in the skin to delayed hypersensitivity antigens and the blood T lymphocyte count and serum C3 levels were low. From these findings and a review of the literature it was concluded that the immune response in man to Strongyloides stercoralis may depend on T lymphocyte mediated reactions including granuloma formation, and mast cell and eosinophil responses in tissues. We suggest that the association of strongyloides hyperinfection and small bowel lymphoma in this patient may not have been fortuitous. The lymphoma may have led to a reduction in cellular immunity, with the subsequent development of strongyloides hyperinfection.

Adult↗

PubMedDate not supplied

[Morphology and biometry of eggs and larvae of Strongyloides sp. Grassi, 1879 (Rhabditoidea: Strongyloididae), a gastrointestinal parasite of Hydrochaeris hydrochaeris (Linnaeus, 1766) (Rodentia: Hydrochaeridae), in the municipality of Juiz de Fora, Minas Gerais, Brazil].

An important method to diagnose and study the helminthofauna of wild animals is to examine the host's feces to find eggs and larvae, seeking to identify the parasites and study their morphobiology. The objective of the present work is to provide morphological and biometric data on the eggs and larvae of Strongyloides sp., a capybara gastrointestinal parasite. Using the technique of Gordon and Whitlock, simple flotation and the modified Baermann examination, capybara fecal samples were selected based on a criterion of the highest proportion of eggs and larvae in the initial development stages, for morphometric description of eggs, L1, L2 and L3 of Strongyloides sp. From past reports of parasitism in Hydrochaeris hydrochaeris, we suspect that the eggs and larvae in this study are of Strongyloides chapini Sandground, 1925, which constitutes the first description of these stages for this species of nematode. Nevertheless, the morphology and biometry data of these stages demonstrate that they are similar to those of other species of the Strongyloides genus.

Animals↗

PubMed1990

Strongyloides cf. fuelleborni and other intestinal helminths in Papua New Guinea: distribution according to environmental factors.

Age graded prevalence rates for Strongyloides cf. fuelleborni, hookworm, Ascaris and Trichuris from various regions of Papua New Guinea were standardised using the standardised mortality technique. Using regression analyses on the resultant Standardised Prevalence Ratios (SPRs) of the four intestinal helminths and rainfall, altitude, slope and relief values, and population density for the various regions no environmental preference was shown which would account for their distribution. However, an examination of parasite distribution in relation to landform and rock type showed that Strongyloides was rare or absent from areas of limestone and polygonal karst although these substrates were quite suitable for other helminths. When the prevalence rates for each of the parasites were separated for high and low altitude (greater than 1,000 and less than 1,000 m a.s.l.) and then age standardised it was shown that there was no difference in hookworm prevalence rates for different altitudes. Both Ascaris and Trichuris had higher prevalences at the higher altitudes, whereas the reverse was true for Strongyloides. The data were also examined to determine whether there was any degree of association between the prevalence of one parasite and another. No association was established between hookworm and Ascaris, hookworm and Trichuris or Ascaris and Trichuris. A positive correlation was demonstrated between hookworm and Strongyloides, although this appears to be a statistical rather than a real association.

Adolescent↗

PubMed1984

Pancreatic cystadenocarcinoma associated with strongyloides.

A 60-year-old woman presented with a mass in the left upper abdominal quadrant. Noninvasive studies showed a cystic structure arising from the pancreas. Pathologic studies of the tumor revealed pancreatic cystadenocarcinoma; the fluid contained Strongyloides larvae. There was no evidence of disseminated Strongyloides or immunosuppression. Results of stool examinations were also negative for Strongyloides. Were these larvae the etiologic agent for the carcinoma? Other parasitic infestations have been associated with carcinoma. This is the first reported association between Strongyloides and cystadenocarcinoma.

Cystadenocarcinoma↗

PubMedDate not supplied

Strongyloides cf. fuelleborni and hookworm in Papua New Guinea: patterns of infection within the community.

The results of quantitative stool examinations from a large number of rural Papua New Guineans permitted the establishment of age-prevalence and age-intensity profiles and frequency distributions of both Strongyloides cf. fuelleborni and hookworm. Strongyloides exhibited a unique age-prevalence profile which originated at about 40% in the youngest age group, rose to a maximum in those 4-5 years old, and then declined. The intensity of infection reached its peak in 12 month olds before declining. The frequency distribution of Strongyloides egg counts was markedly over-dispersed: k values were below 0.1 for most age groups. Both prevalence and intensity of infection curves for hookworm followed similar patterns, which were typical for the parasite, rising to a maximum at about age 9 years, and then forming a plateau. The distribution of hookworm egg counts was less over-dispersed than that of Strongyloides, the k values rising until about 10 years of age and then remaining stable with a value of about 0.7. With both parasites there was little difference in prevalence or intensity of infection between the sexes, although adult males tended to have higher levels for both quantities.

Adolescent↗

PubMed1990

Seroepidemiology of Strongyloides infection in the Southeast Asian refugee population in Canada.

As part of a screening and treatment program for intestinal parasite infections offered to newly arrived Southeast Asian refugees in Canada between July 1982 and February 1983, a total of 232 sera were tested for Strongyloides infection using an enzyme-linked immunosorbent assay (immunoglobulin G). These results were compared with coprologic results and eosinophil counts. The seroprevalence was 76.6% (131 of 171) among Kampucheans, 55.6% (15 of 27) among Laotians, and 11.8% (4 of 34) among Vietnamese. A statistically significant relation (p less than 0.001) was found between Strongyloides serology and Strongyloides infection on stool examination (prevalence, 24.7%) among Kampucheans. Eosinophilia (greater than or equal to 10%) was found to be significantly associated with both infection measures. Using coprologic results as the "gold standard," the properties of the serologic test were estimated to be: sensitivity (95%), specificity (29%), positive predictive value (30%), and negative predictive value (95%). These estimates should be regarded as minimal values, as stool examination for Strongyloides infection can be an unreliable diagnostic reference. Further evaluation of the discrepancies observed between coprologic and serologic testing is required to determine the usefulness of these tests in epidemiologic studies.

Adolescent↗

PubMedDate not supplied

Brain stem glioma complicated by Strongyloides stercoralis.

The simultaneous occurrence of brain stem glioma and disseminated Strongyloides stercoralis infestation in an Ecuadorian male is reported. The unusual finding of Strongyloides larvae in the potassium hydroxide preparation for fungi and in the Gram stain for bacteria from a sputum during hemoptysis fortuitously established the diagnosis of disseminated strongyloidiasis. Of interest was the demonstration of various stages of Strongyloides in the sputum during treatment. Strongyloides infestation must be assiduously searched for in susceptible patients who are, or who are to be, immunosuppressed.

Adult↗

PubMed2005

The beta-tubulin genes of two Strongyloides species.

The World Health Organization is sponsoring major treatment programs with the aim of controlling helminth infection throughout the tropical world. Prominent among the anthelmintics recommended for use in these programs are drugs in the benzimidazole (BZ) class. Resistance to these drugs has been associated with polymorphisms in the beta-tubulin gene. We have cloned and sequenced the beta-tubulin genes of Strongyloides stercoralis and Strongyloides ratti and have proceeded to develop a protocol for genotyping single worms for polymorphisms in beta-tubulin. Our findings indicate that S. ratti has a single beta-tubulin gene, making DNA sequence analysis of a single larva PCR product a feasible means of studying BZ resistance in these species. Our genotyping test allows the identification of polymorphisms at codons 167, 198, and 200 in the Strongyloides beta-tubulin gene, thus enabling survey for BZ resistant genotypes.

3' Untranslated Regions↗

PubMed2006

The biology and genomics of Strongyloides.

Parasitic nematodes are widespread and important pathogens of humans and other animals. The parasitic nematodes Strongyloides have an unusual life cycle in which there is a facultative free-living generation in addition to the obligate parasitic generation. The genomes of many species of parasitic nematodes, including Strongyloides ratti and Strongyloides stercoralis, have been investigated, principally by expressed sequence tag (EST) analyses. These have discovered very many genes from these parasites but, in so doing, have also revealed how different these species are from each other and from other organisms. Understanding the role and function of these newly discovered genes is now the challenge, made more difficult by the parasitic lifestyle. The genomic information available for parasitic nematodes is allowing new approaches for the control of parasitic nematodes to be considered.

Animals↗

PubMed2005

Fatal outcome of a hyperinfection syndrome despite successful eradication of Strongyloides with subcutaneous ivermectin.

We report the case of a 77-year-old man who developed a Strongyloides hyperinfection syndrome following immunosuppressive therapy more than 60 years after he moved away from an area endemic for Strongyloides stercoralis. Successful eradication of the nematode was achieved with an off label subcutaneous formulation of ivermectin. However, the patient subsequently died from acute respiratory distress syndrome (ARDS). Despite a high wormload in the stool and sputum of the patient and delayed infection control measures in the hospital, testing of the medical staff revealed a very low risk of Strongyloides transmission among healthcare workers.

Aged↗

PubMed1987

Strongyloides spp.: demonstration and partial characterization of acidic collagenolytic activity from infective larvae.

Infective larvae of Strongyloides spp. have been shown to contain azocollytic enzymes which may aid in host skin penetration. Attempts to demonstrate classical, neutral pH-active collagenase activity in Strongyloides ratti were unsuccessful. In the current study, we investigated the presence of acidic collagenolytic activity in the infective larvae of Strongyloides ransomi, S. ratti, and S. stercoralis. All three species demonstrated collagenolytic activity in acidic homogenates as well as in neutral freeze-thaw fractions. Biochemical characterization of this collagenolytic activity from S. ratti and S. ransomi indicated that it was active over an acidic pH range, although it was stable at a neutral pH. This, along with molecular weight estimates and inhibitor susceptibilities, suggested that the collagenolytic activity was similar to vertebrate acidic cysteinyl proteinases. These studies also indicated that this activity is similar to the acidic cysteinyl proteinases in extracts of S. ransomi.

Animals↗

PubMed1995

Strongyloides stercoralis: histopathology of uncomplicated and hyperinfective strongyloidiasis in the Mongolian gerbil, a rodent model for human strongyloidiasis [corrected].

Tissues from corticosteroid-treated gerbils hyperinfected with Strongyloides stercoralis were compared grossly and microscopically to similar tissues from animals with uncomplicated strongyloidiasis. Gerbils with hyperinfection developed severe pulmonary alveolar haemorrhage with a variable degree of subacute eosinophilic interstitial pneumonia associated with numerous alveolar, vascular and interstitial larvae. Hyperinfection induced by corticosteroids, given either before inoculation of S. stercoralis larvae or after a chronic Strongyloides infection was established, produced similar lesions. In contrast, lungs from gerbils with uncomplicated Strongyloides infection had severe eosinophilic perivasculitis and vasculitis with very little haemorrhage, no pneumonia and no larvae. Sections of adult worms were present in the proximal part of the intestinal tract, lodged in spaces between mucosal epithelial cells. Adult worms were not associated with inflammation and were more common in the corticosteroid-treated gerbils. In corticosteroid-treated gerbils only, there were numerous larvae in the distal intestinal tract, throughout the intestinal wall and adjacent mesentery, within interstitial tissues and in lymphatic vessels. Significant inflammation with associated larvae was only present in the caecum and mesenteric lymph nodes, suggesting that the caecum was the main site for initiation of parenteral migration with subsequent invasion of the lymphatic system and lungs. The lesions in these gerbils were similar to those found in humans. Infection of gerbils with S. stercoralis is the best rodent model of human strongyloidiasis.

Animals↗

PubMed1982

Infection and immunity in dogs infected with a human strain of Strongyloides stercoralis.

The course of infection and immunological responses in dogs infected with a strain of Strongyloides stercoralis of human origin were investigated. The first dog infected developed a chronic infection lasting at least 15 months. Larvae disappeared from the faeces by three months after infection in another four dogs; these animals were resistant to challenge infection. A further dog developed a chronic infection of low intensity which could not be boosted by repeated heavy infections. These differences may be genetically determined. Immune responses in primary infections were measured in four dogs. A blood eosinophilia occurred in infected animals. Anti-Strongyloides antibodies of the IgM class appeared one week after infection, peaked at three weeks then slowly declined in titre while IgG antibodies appeared slightly later and then persisted in high titre. When compared with uninfected control dogs, no significant differences were seen in PHA stimulation of peripheral blood lymphocytes, nor did significant lymphocyte proliferation occur in the presence of Strongyloides antigen. Infected dogs showed marked immediate hypersensitivity to antigen injected intradermally, but Arthus and delayed hypersensitivity reactions were not seen. This model of human strongyloidiasis merits further investigation.

Animals↗