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At least 19 recordsLinked to original sources
PubMed1991

Species-specific differences in heterogonic development of serially transferred free-living generations of Strongyloides planiceps and Strongyloides stercoralis.

The direction of free-living development (homogonic vs. heterogonic) in Strongyloides stercoralis and Strongyloides planiceps was examined by successive transplantation of the uterine eggs of free-living females into a test tube culture system containing fresh feces. The eggs from the first-generation free-living females of S. stercoralis did not develop into second-generation free-living adult worms, but all developed into filariform larvae. However, the majority of S. planiceps eggs from the first-generation free-living females developed into second-generation free-living adults. By successive transfer of uterine eggs of each generation, 9 generations developed, and in every cycle more adult worms developed than filariform larvae. However, the number of free-living generations was not infinite; in experiments repeated twice, the number of worms developing from the eggs of eighth or ninth generations was too small to continue further culture. These findings indicate that the pattern of free-living development is different between the 2 species.

Animals↗
PubMedDate not supplied

Opportunistic infections with Strongyloides stercoralis in renal transplantation.

Opportunistic infections with the nematode Strongyloides stercoralis occur most often in patients with impaired T lymphocyte function, including recipients of renal allografts. Occult intestinal infection can remain quiescent for more than 30 years, becoming apparent only after the initiation of immunosuppression. Pulmonary and gastrointestinal symptoms predominant as initial clinical manifestations in patients with strongyloides hyperinfection or dissemination. Although thiabendazole remains the treatment of choice for all forms of strongyloidiasis, the duration of therapy must be individualized on the basis of frequent examinations of both stool and sputum. Transplantation centers drawing patients from areas with endemic Strongyloides should evaluate potential recipients closely for occult strongyloides infection prior to initiating immunosuppressive therapy. Empiric therapy with thiabendazole should be considered for renal allograft recipients with unexplained eosinophilia and a history of travel or residence in an area with endemic Strongyloides. Prophylactic monthly administration of thiabendazole in immunocompromised patients who have survived strongyloides hyperinfection or dissemination can prevent reinfection.

Adult↗
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↗
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↗
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↗
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↗
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↗
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↗
PubMedDate not supplied

Diagnosis of Strongyloides and hookworm infections: comparison of faecal and duodenal fluid microscopy.

Faecal microscopical diagnosis of Strongyloides and hookworm infections is insensitive. We have therefore compared duodenal fluid and faecal microscopy for detection of these parasites in a group of 292 patients being investigated for gastrointestinal symptoms who were examined by both techniques. Thirty-three of these patients (8%) were infected with Strongyloides stercoralis and 88 (30%) had hookworm infections. Microscopical examination of up to 3 faecal specimens detected only 33% and 65% of patients with Strongyloides and hookworm infections, respectively. Microscopical examination of a single specimen of duodenal fluid was more sensitive for detection of strongyloidiasis, identifying 76% of patients; the parasite was found exclusively in duodenal fluid (and not in faeces) in 67% of patients. For hookworm, the diagnostic sensitivity was similar with both techniques but duodenal fluid microscopy detected some patients (35%) who had not been identified by faecal microscopy. This study confirms previous work indicating the insensitivity of faecal microscopy in these infections and emphasizes the need to consider routine examination of duodenal fluid to exclude chronic strongyloidiasis. This may have particular relevance for south-east Asian war veterans and immunocompromised patients.

Ancylostomatoidea↗
PubMed1990

An evaluation of the agar plate method for the detection of Strongyloides stercoralis in northern Thailand.

An examination of the stools from school-children in northern Thailand was performed in order to compare the efficacy of a new method--the agar plate method--for the detection of Strongyloides stercoralis with traditional methods. Twenty-three positive specimens (15.5%) from a total of 148 specimens were detected as follows: 18 cases by the agar plate method, 13 cases by direct stool smear, 11 cases by filter paper culture, and four cases by the formalin-ether method (MGL). On the basis of the above results, the agar plate method appeared to be more efficient than traditional methods for detecting Strongyloides in human stool samples. Other positive factors in its favour were ease of manipulation and low cost. There were some problems with using this method. Five cases shown to be positive by traditional methods were negative in the agar plate method, and it was necessary to discriminate Strongyloides microscopically from other similar nematode larvae, especially in an area, such as northern Thailand, with a high prevalence of hookworms.

Animals↗
PubMed1986

[Effectiveness of ivermectin in Strongyloides westeri cases in foals].

Efficacy of Ivermectin in combating Strongyloides westeri infection of foal. The efficacy of Ivermectin and Mebendazol in combating spontaneous Strongyloides westeri infections in foals has been tested by examining faecal egg output reduction. Ivermectin as a paste formulation was given to sucking foals and pregnant mares in a single dosage of 200 micrograms/kg bodyweight by oral administration. A high efficacy of Ivermectin in combating patent Strongyloides westeri infection could be demonstrated; no side effects have been observed. Mebendazol at a dosage rate of 8 mg/kg did not yield satisfactory results.

Animals↗
PubMed1977

Cytology, reproduction, and sex determination of Strongyloides ransomi and S. papillosus.

Parasitic females of Strongyloides ransomi and Strongyloides papillosus have 4 chromosomes and reproduce exclusively by mitotic (apomictic) parthenogenesis. The free-living generation includes females and males. The females have 2 pairs of chromosomes of unequal size and reproduce by meiotic parthenogenesis following obligatory pseudofertilization (gynogenesis). The males undergo spermatogenesis by the regular meiotic process and have the same chromosomal complement as the females. During prophase I, however, a portion of one homologue of the large bivalent breaks free and subsequently is diminished, as in S. ransomi, or it rejoins the original homologue, as in S. papillosus. This behavior of meiotic chromosomes during spermatogenesis suggests that the karyotype of these species has evolved from a karyotype analogous to that of Strongyloides ratti with 2 pairs of autosomes and a pair of X chromosomes, following fusion of the X chromosome with an autosome and the formation of a Neo-X and a Neo-Y chromosome. The female karyotype of S. ransomi and S. papillosus thus may be 2A + 2 Neo-X. The males are phenotypic males and have the same karyotype as the females, but their functional karyotype may be 2A + Neo-X + Neo-Y.

Animals↗
PubMed1987

An intervention study using thiabendazole suspension against Strongyloides fuelleborni-like infections in Papua New Guinea.

In an isolated rural community in Papua New Guinea, 88 children were found to be infected with Strongyloides cf. fuelleborni; 50 of these also had hookworm infections. Their ages ranged from one to 124 months and all were treated with thiabendazole suspension, 25 mg/kg twice daily for 3 days. 2 patients with Strongyloides and 5 with hookworm were still passing ova 2 weeks after treatment although their egg counts were lower or the same as the pre-treatment counts. 26 children experienced some side effects from the drug, vomiting being the most common; in none did side effects prevent completion of therapy. No association between Strongyloides egg load and nutritional status, hepatosplenomegaly, respiratory ailments, oedema or serum albumin levels was found.

Child↗
PubMed1989

Strongyloides and hookworm in Papua New Guinea: longitudinal studies on treated and untreated children.

Helminth egg counts were made on 86 treated and 38 untreated children in an isolated Papua New Guinea community before treatment and on nine subsequent occasions over an 18-month period. No predisposition could be detected to heavy or light infection with hookworm, either in the rate of reinfection or in the maximum post-treatment egg counts. Indications of predisposition in Strongyloides cf. fuelleborni were not statistically significant. In untreated children, sequential age-standardized hook-worm egg counts remained significantly correlated with each other at time lags up to nine months, but those for Strongyloides showed good correlation if made up to 14 months apart. Possible explanations include a surprising longevity of Strongyloides worms or unexpected external auto-infection.

Animals↗
PubMed1986

Pancreatic mass due to Strongyloides stercoralis infection: an unusual manifestation.

A 30-year-old man returning from a trip through India complained of epigastric pain, diarrhea, loss of weight, and jaundice. Stool examination was positive for Strongyloides stercoralis. On ultrasonographic investigation, intravenous cholangiography, and endoscopic retrograde cholangiopancreaticography, stenosis of the distal common bile duct and enlargement of the pancreatic head were observed. The patient was treated for the Strongyloides infection. The jaundice disappeared within days, the laboratory finding normalized, and the patient recovered rapidly. However, the ultrasonographic examination showed a complete recovery in the course of about 2 years. From this report we conclude that in patients with obstructive jaundice and Strongyloides stercoralis infection, serious abnormalities resembling pancreatic tumour or pancreatitis can be found on ultrasonographic and radiological investigations, and this should be considered in the differential diagnosis of pancreatic mass in patients living in or returning from endemic areas.

Adult↗
PubMed1987

Strongyloides stercoralis hyperinfection in a patient with the acquired immune deficiency syndrome.

Severe infections with Strongyloides stercoralis occur in immunocompromised patients. Strongyloides hyperinfection syndrome complicated by gram-negative bacteremia and meningitis in a bisexual man with the acquired immune deficiency syndrome (AIDS) is described. Increased awareness of this infection, which may also be sexually transmitted, is recommended when caring for patients with AIDS who are homosexual, or have resided in areas endemic for strongyloidiasis. Multiple stool examinations should be performed routinely for such patients. Examination of sputum for the parasite is recommended if pneumonia is present. Prompt diagnosis and therapy are essential for prevention of fatal dissemination.

Acquired Immunodeficiency Syndrome↗