Human Strongyloidiasis Research Articles

Migratory route of Strongyloides venezuelensis in Lewis rats: Comparison of histological analyses and PCR

Strongyloides venezuelensis is a parasitic nematode that has been used as a model to study human and animal strongyloidiasis. In this study, we compared the sensitivity between traditional methodologies and PCR assay to characterize the dynamics of S. venezuelensis infection and its migration route in Lewis rats subcutaneously infected with 4000 L3. The dynamics of the infection was determined by counting the number of eggs and by detecting parasite deoxyribonucleic acid in faeces samples. Both techniques similarly detected the infection at day 6 after larvae inoculation. However, PCR performed with the genus primer showed higher sensitivity during the recovery phase. Histological analysis and PCR assay were then used to follow parasite tissue migration. S. venezuelensis migration route included the muscular fibers below the skin, the pulmonary alveoli and the small intestine vilosities. The sensitivity of these two techniques to detect parasite’s presence in these tissues was statistically similar.

Molecular identification of the causative agent of human strongyloidiasis acquired in Tanzania: Dispersal and diversity of Strongyloides spp. and their hosts

In order to identify the causative agent of imported strongyloidiasis found in a Japanese mammalogist, who participated in a field survey in Tanzania, the hyper-variable region IV (HVR-IV) of 18S ribosomal DNA and partial mitochondrial cytochrome c-oxidase subunit 1 gene ( cox1) were analyzed and compared with Strongyloides fuelleborni collected from apes and monkeys of Africa and Japan, and S. stercoralis from humans, apes and dogs. The HVR-IV and cox1 of the patient's worms were identical to or only slightly differed from those of worms parasitic in Tanzanian chimpanzees and yellow baboons, demonstrating that the patient acquired the infection during her field survey in Tanzania. Phylogenetic analysis with the maximum-likelihood method largely divided isolates of S. fuelleborni into three groups, which corresponded to geographical localities but not to host species. Meanwhile, isolates of S. stercoralis were grouped by the phylogenetic analysis into dog-parasitic and primate-parasitic clades, and not to geographical regions. It is surmised that subspeciation has occurred in S. fuelleborni during the dispersal of primates in Africa and Asia, while worldwide dispersal of S. stercoralis seems to have occurred more recently by migration and the activities of modern humans.

Hydrophobic fractions from Strongyloides venezuelensis for use in the human immunodiagnosis of strongyloidiasis

The objective of the present research was to evaluate detergent and aqueous phases of total saline (TS) and alkaline extracts of Strongyloides venezuelensis for human strongyloidiasis immunodiagnosis. Total extracts and detergent and aqueous antigenic fractions were separated using Triton X-114 and were examined by enzyme-linked immunosorbent assay (ELISA) and immunoblotting (IB) tests to detect immunoglobulin G (IgG). Serum samples were obtained from 120 individuals: 40 strongyloidiasis patients (group I), 40 patients with other parasitic diseases (group II), and 40 apparently healthy individuals (group III). Each extract provided a different profile of antigenic components as recognized by IgG in IB. The detergent fraction of the TS extract demonstrated the highest sensitivity and specificity for ELISA and IB. The results indicated that the detergent saline fraction, purified from S. venezuelensis, furnished the most valid results for the strongyloidiasis immunodiagnosis and could be employed as an alternative antigen and as a useful source of specific polypeptides.

Factors Affecting Recovery of Strongyloides stercoralis Larvae: an Approach to a Newly Modified Formalin-Ether Concentration Technique for Diagnosis of Strongyloidiasis

To improve the diagnosis efficiency of human strongyloidiasis by using formalin-ether concentration technique (FECT), the effects of various factors on the recovery rates of Strongyloides stercoralis larvae were comparatively evaluated. Fresh stool and a short time exposure of larvae to formalin yielded significantly higher numbers of larvae than preserved stool and 10-min exposure. Likewise, straining through wire mesh yielded a significantly higher number of larvae recovered than straining through gauze did. In addition, centrifugation for 5 min for separation of larvae from debris yielded a significantly greater number of larvae recovered than centrifugation for 2 min did. The efficacies of the five versions of FECT with different factors--FECT 1, FECT 2, FECT 3, FECT 4, and FECT 5--were then compared. It was found that FECT 5 was 1.8, 2.0, 1.9, and 1.4 times more effective than FECT 1, FECT 2, FECT 3, and FECT 4, respectively. FECT 5 is a modified FECT method, whose modifications included using fresh stool without a preservative substance; a short-time rather than 10-min formalin exposure; and the use of wire mesh instead of gauze.

Regulatory T Cell Expansion in HTLV-1 and Strongyloidiasis Co-infection Is Associated with Reduced IL-5 Responses to Strongyloides stercoralis Antigen

BackgroundHuman strongyloidiasis varies from a chronic but limited infection in normal hosts to hyperinfection in patients treated with corticosteroids or with HTLV-1 co-infection. Regulatory T cells dampen immune responses to infections. How human strongyloidiasis is controlled and how HTLV-1 infection affects this control are not clear. We hypothesize that HTLV-1 leads to dissemination of Strongyloides stercoralis infection by augmenting regulatory T cell numbers, which in turn down regulate the immune response to the parasite.ObjectiveTo measure peripheral blood T regulatory cells and Strongyloides stercoralis larval antigen-specific cytokine responses in strongyloidiasis patients with or without HTLV-1 co-infection.MethodsPeripheral blood mononuclear cells (PBMCs) were isolated from newly diagnosed strongyloidiasis patients with or without HTLV-1 co-infection. Regulatory T cells were characterized by flow cytometry using intracellular staining for CD4, CD25 and FoxP3. PBMCs were also cultured with and without Strongyloides larval antigens. Supernatants were analyzed for IL-5 production.ResultsPatients with HTLV-1 and Strongyloides co-infection had higher parasite burdens. Eosinophil counts were decreased in the HTLV-1 and Strongyloides co-infected subjects compared to strongyloidiasis-only patients (70.0 vs. 502.5 cells/mm3, p = 0.09, Mann-Whitney test). The proportion of regulatory T cells was increased in HTLV-1 positive subjects co-infected with strongyloidiasis compared to patients with only strongyloidiasis or asymptomatic HTLV-1 carriers (median = 17.9% vs. 4.3% vs. 5.9 p<0.05, One-way ANOVA). Strongyloides antigen-specific IL-5 responses were reduced in strongyloidiasis/HTLV-1 co-infected patients (5.0 vs. 187.5 pg/ml, p = 0.03, Mann-Whitney test). Reduced IL-5 responses and eosinophil counts were inversely correlated to the number of CD4+CD25+FoxP3+ cells.ConclusionsRegulatory T cell counts are increased in patients with HTLV-1 and Strongyloides stercoralis co-infection and correlate with both low circulating eosinophil counts and reduced antigen-driven IL-5 production. These findings suggest a role for regulatory T cells in susceptibility to Strongyloides hyperinfection.

Cross Infection of Strongyloides between Humans and Dogs in the Amami Islands, Japan

Human strongyloidiasis is a parasitic infection induced by the nematode Strongyloides stercoralis which can cause gastrointestinal disturbances. It is believed to be a zoonosis with a potential for cross infection between humans and dogs. The aim of this work was to study this cross infection. Epidemiological surveys of human intestinal parasites were carried out using direct smears and cultures in the Amami Islands during the summer season from 2003 to 2008. Stools were collected from people and dogs inhabiting the Amami Islands, I.e., Kikai, Amami, Kakeroma, Uke, Yoro and Okinoerabu, Japan. It was confirmed that the infective ratio of Strongyloides was 2.8% of 660 residents studied and 10.0% of their 55 dogs. The owners who had parasite-carrier dogs were not found to have parasites, and, conversely the dogs who were kept by owners having parasites were free of parasites. The epidemiological results of the present study demonstrate that natural infection of Strongyloides does not occur between humans and dogs.

Specific IgA and IgG antibodies in paired serum and breast milk samples in human strongyloidiasis

Strongyloidiasis, caused by the nematode Strongyloides stercoralis, is one of the major worldwide parasitic infections in humans. Breastfeeding may offer a potential protection against this infection. Feces, serum and milk samples were obtained from 90 lactating women from Clinical Hospital of Universidade Federal de Uberlândia, Brazil. The fecal samples were collected for parasitological diagnosis and the serum and milk samples were examined for specific S. stercoralis IgA and IgG antibodies using the indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA). Fecal examination showed that the rate of prevalence of S. stercoralis infection in the lactating women was 4.4%. IFAT manifested a 16.7% positivity rate for specific IgA antibody in serum and a 28.9% rate in milk samples; specific IgG was 41.1% in serum and 25.5% in milk samples. According to ELISA the positivity rate for specific IgA antibody was 21.1% in serum and 42.2% in milk samples; specific IgG was 40% in serum and 18.9% in milk samples. In serum samples, these immunological tests showed a concurrence of 91.1% and 94.4%, respectively, in detecting specific IgA and IgG antibodies. In milk samples, they showed a concurrence of 70% and 78.9%, respectively, in detecting specific IgA and IgG antibodies. There was a statistically significant difference between concordant and discordant results of immunological tests ( P < 0.0001). IFAT and ELISA highly concurred in their detection of specific S. stercoralis IgA and IgG antibodies in serum and in milk samples reconfirming prior studies that the serological method is a complement to the direct diagnosis of the parasite, and suggesting that immunological methods using milk samples can also be helpful. Furthermore, in endemic areas, infants may acquire antibodies to S. stercoralis from breast milk, possibly, contributing to the enhancement of specific mucosal immunity against this parasite.

Strongyloides venezuelensis: The antigenic identity of eight strains for the immunodiagnosis of human strongyloidiasis

The antigens of eight strains of Strongyloides venezuelensis were identified by means of the indirect immunofluorescence antibody (IFAT), enzyme-linked immunosorbent assay (ELISA) and immunoblot (IB) tests. Infective larvae (L3) from these strains were obtained from Rattus norvegicus feces cultures. For IFAT, sections of L3 were used while the ELISA and IB, tests were conducted with alkaline extract. Ninety serum samples were tested: 30 from patients with S. stercoralis, 30 from patients with other parasitic diseases, and 30 from healthy subjects (free of parasites). Average sensitivity and specificity among all eight strains, both for IFAT and ELISA, were, respectively, 93% and 100%. In the IB, anti-S. stercoralis IgG recognized a single antigenic fraction with 45kDa. Serum samples from patients with S. stercoralis revealed antigens from different strains of S. venezuelensis, indicating antigenic identity for possible use in the synthesis of recombinant antigen that could be useful in immunodiagnosis and vaccine against this parasite.

IgG1, IgG4, and IgE antibody responses in human strongyloidiasis by ELISA using Strongyloides ratti saline extract as heterologous antigen

The aim of this study was to evaluate total IgG, IgG1, IgG4, and IgE antibody responses in human strongyloidiasis by enzyme-linked immunosorbent assay (ELISA) using Strongyloides ratti saline extract as heterologous antigen for a possible clinical utility of the assay. A total of 40 serum samples of patients who were shedding Strongyloides stercoralis larvae in feces (group I), 30 sera from patients with other intestinal parasites (group II), and 30 sera from subjects with negative results in three parasitological assays (group III) were analyzed to detect total IgG, IgG1, IgG4, and IgE to Strongyloides spp. by ELISA and expressed in ELISA index. Levels of total IgG anti-Strongyloides spp. were significantly higher in patients of group I than in groups II (p=0.0005) and III (p<0.0001). Levels of specific IgG1, IgG4, and IgE of group I were also significantly higher than in groups II and III, respectively. There was a significant positive correlation between specific IgE and IgG4 (r=0.6524; p=0.0084) and IgG1 and IgG4 (r=0.5398; p=0.0171). It can be concluded that the detection of specific IgE, IgG1, and IgG4 subclasses rather than total IgG antibodies to Strongyloides spp. using the S. ratti antigen showed to be an additional tool for improving the serodiagnosis of human strongyloidiasis.

Evaluation of strongyloidiasis in kennel dogs and keepers by parasitological and serological assays

Strongyloides stercoralis is an intestinal nematode with worldwide distribution, particularly in tropical and subtropical regions. Due to the low sensitivity of traditional parasitological methods, the detection of serum specific antibodies may serve as an alternative test for the diagnosis. The aims of the present study were to verify the occurrence of S. stercoralis and the presence of specific IgG antibodies to the parasite in kennel dogs and keepers, using parasitological and serological assays. A total of 181 dogs were examined from 7 breeding kennels in the city of Uberlândia, southeastern region of Brazil and distributed as follows: kennel A ( n = 41), kennel B ( n = 16), kennel C ( n = 11), kennel D ( n = 63), kennel E ( n = 11), kennel F ( n = 18) and kennel G ( n = 21). Fecal and serum samples from 11 keepers responsible for kennel cleaning and dog control were also collected in five of the seven kennels (two from kennel A, one from kennel B, four from kennel D, two from kennel E and two from kennel G). Overall, enteroparasites were detected by parasitological assays in 66, 36.5% (95% CI: 2.5–43.4%) of the 181 dogs tested. Only one (0.6%) dog was copropositive for S. stercoralis. Among the keepers only one fecal sample, 9.1% (95% CI: 8.6–9.4%) was positive for hookworm by the Lutz method. Serological assays showed that 44 (24.3%) of the 181 dogs were seropositive for S. stercoralis in at least one of the tests in the following kennels: 21 (11.6%) in kennel A; 1 (0.6%) in kennel B; 5 (2.7%) in kennel C; 6 (3.3%) in kennel D; 1 (0.6%) in kennel E; 9 (4.9%) in kennel F and 1 (0.6%) in kennel G. Among the keepers no S. stercoralis seropositive samples were identified using IFAT but 2 (18.2%) of the keepers from kennel D and 1 (9.1%) from kennel G were seropositive by ELISA. The present study demonstrated that the occurrence of S. stercoralis infection in kennel dogs and keepers is low in the city of Uberlândia and that serological assays can contribute to the diagnosis of canine as well as human strongyloidiasis.

Comparison of the Quantitative Formalin Ethyl Acetate Concentration Technique and Agar Plate Culture for Diagnosis of Human Strongyloidiasis

The quantitative formalin ethyl acetate concentration technique (QFEC) was compared to agar plate culture (APC) for the detection of Strongyloides stercoralis larvae. QFEC could substitute for APC only when the parasite load was higher than 50 larvae per g of stool. This study serves as a good reminder to those conducting stool exams about the sensitivity and specificity limitations of both techniques.

Strongyloides ratti antigenic components recognized by IgE antibodies in immunoblotting as an additional tool for improving the immunodiagnosis in human strongyloidiasis

IgE antibody response in human strongyloidiasis was evaluated by enzyme-linked immunosorbent assay (ELISA) and immunoblotting (IB) using Strongyloides ratti saline extract as heterologous antigen. A total of 50 serum samples of patients who were shedding S. stercoralis larvae in feces (group I, copropositive), 38 of patients with other intestinal parasites (group II), and 38 of subjects with negative results in three parasitologic assays (group III, copronegative) were analyzed. Levels of IgE anti-Strongyloides expressed in ELISA Index (EI) were significantly higher in patients of group I (1.32) than in group II (0.51) and group III (0.81), with positivity rates of 54%, 0%, and 10.5%, respectively. Fifteen S. ratti antigenic components were recognized in IB-IgE by sera of group I, with frequency ranging from 8% to 46%. In group II, only two antigenic bands (101, 81 kDa) were detected in a frequency of 10% and no reactivity was found in group III. Sera with EI values > 1.5 recognized five from 13 specific antigenic bands (70, 63, 61, 44, 7 kDa). It can be concluded that these five antigenic components recognized by IB-IgE using S. ratti antigen might be employed as an additional tool for improving the immunodiagnosis in human strongyloidiasis.

English

Ivermectin is the drug of choice in the treatment of onchocerciasis, and has been proven to be highly effective against Strongyloides stercoralis. This study compares ivermectin's efficacy and safety with that of thiabendazole, an established drug of choice for strongyloidiasis, in 252 confirmed cases of uncomplicated human intestinal strongyloidiasis. Subjects were administered orally with ivermectin (200 mg/kg) in a single dose or thiabendazole, 25 mg/kg, twice daily (50mg/kg/day) for 3 consecutive days. Stools were parasitologically examined 7, 21 and 30 days after treatment. Only 18 of 113 and 22 of 103 ivermectin- and thiabendazole-treated subjects, respectively, had stools positive for larvae 30 days post-treatment. This indicates parasitological cure rates of 84.07% and 78.64% for ivermectin and thiabendazole, respectively. Ivermectin was not significantly more effective than thiabendazole (P Key words : Ivermectin, thiabendazole, Strongyloides stercoralis, strongyloidiasis. African Journal of Biotechnology Vol.2(11) 2003: 465-469

Heterologous antigen extract in ELISA for the detection of human IgE anti-Strongyloides stercoralis.

Strongyloides ratti larval extract was used for the standardization of ELISA to detect genus-specific IgE in human strongyloidiasis. Forty serum samples from monoinfected patients shedding S. stercoralis larvae (Group I), 40 from patients with other intestinal parasites (Group II), and 40 from copronegative healthy subjects (Group III) were analyzed. Genus-specific IgE levels (ELISA Index: EI) were significantly higher in the group I (EI = 1.43) than groups II (EI = 0.70) and III (EI = 0.71), showing positivity rates of 55%, 2.5% and 0%, respectively. Similarly, sera from copropositive patients had significantly higher levels of total IgE (866 IU/mL) as compared to those from group II (302 IU/mL) and III (143 IU/mL). A significant positive correlation was found between levels of Strongyloides specific-IgE and total IgE in sera from patients with strongyloidiasis. In conclusion, S. ratti heterologous extract showed to be a useful tool for detecting genus-specific IgE by ELISA, contributing for a better characterization of the immune response profile in human strongyloidiasis.

Strongyloides venezuelensis alkaline extract for the diagnosis of human strongyloidiasis by enzyme-linked immunosorbent assay.

The present study was conducted to detected IgG antibodies using Strongyloides venezuelensis alkaline extract for the diagnosis of human strongyloidiasis by the enzyme-linked immunosorbent assay (ELISA). Sera from 90 subjects were analyzed (30 with strongyloidiasis, 30 with other parasites and 30 healthy individuals). Results were expressed in antibody titers, which were considered as positive when titer was >80. Sensibility and specificity of the assay were 100% and 96.7%, respectively. It can be concluded that the heterologous alkaline extract could be employed in ELISA as a diagnostic aid in human strongyloidiasis, due to its advantages as easiness of obtaining, practicability in preparing, and high indexes of sensitivity and specificity.

Western blotting using Strongyloides ratti antigen for the detection of IgG antibodies as confirmatory test in human strongyloidiasis.

The present study was conducted to evaluate the frequency of antigenic components recognized by serum IgG antibodies in Western blotting (WB) using a Strongyloides ratti larval extract for the diagnosis of human strongyloidiasis. In addition, the WB results were compared to the enzyme-linked immunosorbent assay (ELISA) and the indirect immunofluorescence antibody test (IFAT) results. Serum samples of 180 individuals were analyzed (80 with strongyloidiasis, 60 with other intestinal parasitoses, and 40 healthy individuals). S. ratti was obtained from fecal culture of experimentally infected Rattus rattus. For IFAT, S. ratti larvae were used as antigen and S. ratti larval antigenic extracts were employed in WB and ELISA. Eleven S. ratti antigenic components were predominantly recognized by IgG antibodies in sera of patients with strongyloidiasis. There was a positive concordance for the three tests in 87.5% of the cases of strongyloidiasis. The negative concordance in the three tests was 94% and 97.5%, in patients with other intestinal parasitoses and healthy individuals, respectively. In cases of positive ELISA and negative IFAT results, diagnosis could be confirmed by WB. ELISA, IFAT, and WB using S. ratti antigens showed a high rate of sensitivity and specificity. In conclusion, WB using S. ratti larval extract was able to recognize 11 immunodominant antigenic components, showing to be a useful tool to define the diagnosis in cases of equivocal serology.

Diagnosis of Human Strongyloidiasis Using Particulate Antigen of Two Strains of Strongyloides venezuelensis in Indirect Immunofluorescence Antibody Test

Machado, E. R., Ueta, M. T., Gonçalves-Pires, M. R. F., Alves de Oliveira, J. B., Faccioli, L. H., and Costa-Cruz, J. M. 2001. Diagnosis of human strongyloidiasis using particulate antigen of two strains of Strongyloides venezuelensis in indirect immunofluorescence antibody test. Experimental Parasitology99, 52–55.

The prevalence of enteropathy due to strongyloidiasis in Puerto Maldonado (Peruvian Amazon).

Human strongyloidiasis is an important health problem in the southeast region of Peruvian Amazon, due to its prevalence and long term morbidity. An epidemiological study was conducted in the Peruvian Amazon area of Puerto Maldonado to determine the prevalence of strongyloidiasis in the population. Stool samples were collected from 1,133 patients at the outpatient department of our clinic. Strongyloidiasis affected 221 examined patients (20%). Prevalence was highest in males, mostly in children and elderly men. People living in urban and marginal urban areas, those coming from outside the region, and Andean people, showed the highest prevalences. Pre-school children were more likely to be parasitized than older children. The most common symptoms were diarrhea (55%), abdominal pain (32%) and cough (53%). One in 7 (13%) affected patients presented with moderate or severe symptoms, including life-threatening complications. Other intestinal parasites were found frequently in patients diagnosed with strongyloidiasis. Improved human waste disposal services are considered to be the main requirement to reduce the high prevalence of this disease.

L3 antigen-specific antibody isotype responses in human strongyloidiasis: correlations with larval output.

Autoinfective strongyloidiasis is potentially fatal, yet the majority of infected individuals harbour asymptomatic and chronic infections. The role of humoral responses in modulating autoinfection was assessed by examining antibody isotype responses to filariform larval antigens amongst chronically infected ex-Far East Prisoners of War (exFEPOWs) with longstanding (> 30 years) infection. Serum immunoglobulin (Ig)G1, IgG4, IgE and IgA responses to whole Strongyloides stercoralis L3 extracts and their constituent antigenic components were characterized by ELISA and quantitative immunoblotting. Comparison of two groups of S. stercoralis infected exFEPOWs with and without detectable larvae in stool demonstrated novel trends. Significantly enhanced recognition of six immunodominant antigenic components by IgA was associated with undetectable larval output, as was enhanced IgE recognition of several components. Additionally, IgE and IgG4 exhibited parallel antigen recognition patterns. These findings are consistent with roles for IgA in modulating larval output, for IgE in regulating autoinfection, and for IgG4 in blocking IgE-mediated responses in human strongyloidiasis.

Differentially enhanced cytokine gene expression in CD4+ and CD8+ T cells in mesenteric lymph nodes in rats infected with Nippostrongylus brasiliensis.

Autoinfective strongyloidiasis is potentially fatal, yet the majority of infected individuals harbour asymptomatic and chronic infections. The role of humoral responses in modulating autoinfection was assessed by examining antibody isotype responses to filariform larval antigens amongst chronically infected ex-Far East Prisoners of War (exFEPOWs) with longstanding (> 30 years) infection. Serum immunoglobulin (Ig)G1, IgG4, IgE and IgA responses to whole Strongyloides stercoralis L3 extracts and their constituent antigenic components were characterized by ELISA and quantitative immunoblotting. Comparison of two groups of S. stercoralis infected exFEPOWs with and without detectable larvae in stool demonstrated novel trends. Significantly enhanced recognition of six immunodominant antigenic components by IgA was associated with undetectable larval output, as was enhanced IgE recognition of several components. Additionally, IgE and IgG4 exhibited parallel antigen recognition patterns. These findings are consistent with roles for IgA in modulating larval output, for IgE in regulating autoinfection, and for IgG4 in blocking IgE-mediated responses in human strongyloidiasis.