Frequency of human toxocariasis in Jos, Plateau State, Nigeria

The enzyme-linked immunosorbent assay (Elisa) was used to examine sera of 104 children and adults in Jos, Plateau State, Nigeria for anti-toxocaral antibodies, out of which 31 (29.8%) were reactive. The seropositive rates were 30.4% for adults, 29.6% for children, 34% for females and 25.9% for males. However, the differences were not significant by age and sex. A highly significant association (p < 0.001) was observed between seropositivity and geophagia but none between seropositivity and dog ownership (p > 0.05).

Malaria vectors in the municipality of Serra do Navio, State of Amapá, Amazon Region, Brazil

We conducted a survey to determine the vectors of malaria in six localities of Serra do Navio municipality, State of Amapá, from 1990 to 1991. Malaria infection rates of 29.3%, 6.2% and 20.4% were detected by human blood smears in Colônia Água Branca, Porto Terezinha and Arrependido, respectively. There was no malaria infection detected in Serra do Navio. Fifteen species were identified among 3,053 anopheline mosquitoes collected by human bait and 64.4% were identified as Anopheles albitarsis s.l., 16.7% An. braziliensis, 9.5% An. nuneztovari and 5.8% An. triannulatus. An. darlingi, the main vector of malaria in the Amazon region of Brazil, was scare. Using enzyme-linked immunosorbent assay (ELISA), a total positive rate of 0.8% (23/2876) was found for six species: fifteen An. albitarsis s.l., four An. nuneztovari, and one of each: An. braziliensis, An. triannulatus, An. oswaldoi and An. rangeli. Nine of 23 positive mosquitoes were infected with Plasmodium malariae, eight with P. vivax VK210, three with P. vivax VK247 and three with P. falciparum. Since An. albitarsis s.l. was collected feeding on humans, was present in the highest density and was positive by ELISA for malaria sporozoites, it probably plays an important role in malaria transmission in this area.

Serodiagnosis of chronic Chagas infection by using EIE-Recombinant-Chagas-Biomanguinhos kit

A kit based on an enzyme immunoassay, EIE-Recombinant-Chagas-Biomanguinhos, developed by the Oswaldo Cruz Foundation, was evaluated for the serodiagnosis of chronic Chagas disease. Evaluation was performed with 368 serum samples collected from individuals living in an endemic area for Chagas disease: 131 patients in the chronic phase with confirmed clinical, epidemiological, and serological diagnosis (indirect immunofluorescence, indirect hemagglutination or enzyme-linked immunosorbent assay) and 237 nonchagasic seronegative individuals were considered negative control. The EIE-Recombinant-Chagas-Biomanguinhos kit showed high sensitivity, 100% (CI 95%: 96.4-100%) and high specificity, 100% (CI 95%: 98-100%). The data obtained were in full agreement with clinical and conventional serology data. In addition, no cross-reaction was observed with sera from patients with cutaneous (n=14) and visceral (n=3) leishmaniasis. However, when these sera were tested by conventional serological assays for Chagas disease, cross-reactions were detected in 14.3% and 33.3% of the patients with cutaneous and visceral leishmaniasis, respectively. No cross-reactions were observed when sera from nonchagasic seronegative patients bearing other infectious disease (syphilis, n=8; HTLV, n=8; HCV, n=7 and HBV, n=12) were tested. In addition, sera of patients with inconclusive results for Chagas disease by conventional serology showed results in agreement with clinical evaluation, when tested by the kit. These results are relevant and indicate that the refered kit provides a safe immunodiagnosis of Chagas disease and could be used in blood bank screening.

An improved method for concentrating rotavirus from water samples

A modified adsorption-elution method for the concentration of seeded rotavirus from water samples was used to determine various factors which affected the virus recovery. An enzyme-linked immunosorbent assay was used to detect the rotavirus antigen after concentration. Of the various eluents compared, 0.05M glycine, pH 11.5 gave the highest rotavirus antigen recovery using negatively charged membrane filtration whereas 2.9% tryptose phosphate broth containing 6% glycine; pH 9.0 was found to give the greatest elution efficiency when a positively charged membrane was used. Reconcentration of water samples by a speedVac concentrator showed significantly higher rotavirus recovery than polyethylene glycol precipitation through both negatively and positively charged filters (p-value <0.001). In addition, speedVac concentration using negatively charged filtration resulted in greater rotavirus recovery than that using positively charged filtration (p-value = 0.004). Thirty eight environmental water samples were collected from river, domestic sewage, canals receiving raw sewage drains, and tap water collected in containers for domestic use, all from congested areas of Bangkok. In addition, several samples of commercial drinking water were analyzed. All samples were concentrated and examined for rotavirus antigen. Coliforms and fecal coliforms (0->1,800 MPN/100 ml) were observed but rotavirus was not detected in any sample. This study suggests that the speedVac reconcentration method gives the most efficient rotavirus recovery from water samples.

High prevalence anti-Trypanosoma cruzi antibodies, among blood donors in the State of Puebla, a non-endemic area of Mexico

Blood transfusion is the second most common transmission route of Chagas disease in many Latin American countries. In Mexico, the prevalence of Chagas disease and impact of transfusion of Trypanosoma cruzi-contaminated blood is not clear. We determined the seropositivity to T. cruzi in a representative random sample, of 2,140 blood donors (1,423 men and 647 women, aged 19-65 years), from a non-endemic state of almost 5 millions of inhabitants by the indirect hemagglutination (IHA) and enzyme linked immunosorbent assay (ELISA) tests using one autochthonous antigen from T. cruzi parasites, which were genetically characterized like TBAR/ME/1997/RyC-V1 (T. cruzi I) isolated from a Triatoma barberi specimen collected in the same locality. The seropositivity was up to 8.5% and 9% with IHA and ELISA tests, respectively, and up to 7.7% using both tests in common. We found high seroprevalence in a non-endemic area of Mexico, comparable to endemic countries where the disease occurs, e.g. Brazil (0.7%), Bolivia (13.7%) and Argentina (3.5%). The highest values observed in samples from urban areas, associated to continuous rural emigration and the absence of control in blood donors, suggest unsuspected high risk of transmission of T. cruzi, higher than those reported for infections by blood e.g. hepatitis (0.1%) and AIDS (0.1%) in the same region.

Prevalence of Toxocara infection in schoolchildren from the Butantã region, São Paulo, Brazil

Visceral larva migrans syndrome by Toxocara affects mainly children between 2 and 5 years of age, it is generally asymptomatic, and the seroprevalence varies from 3 to 86% in different countries. A total of 399 schoolchildren from 14 public schools of the Butantã region, São Paulo city, Brazil, were evaluated by Toxocara serology (enzyme-linked immunosorbent assay). Epidemiological data to the Toxocara infection obtained from a protocol were submitted to multiple logistic regression analysis for a risk profile definition. Blood was collected on filter paper by finger puncture, with all samples tested in duplicate. Considering titers > 1/160 as positive, the seroprevalence obtained was 38.8%. Among infected children, the mean age was 9.4 years, with a similar distribution between genders. A significant association was observed with the presence of onychophagia, residence with a dirty backyard, living in a slum, previous wheezing episodes, school attended, and family income (p < 0.05). All data, except "living in a slum", were considered to be determinant of a risk profile for the acquisition of Toxocara infection. A monthly income > 5 minimum salaries represented a protective factor, although of low relevance. Toxocara eggs were found in at least one of the soil samples obtained from five schools, with high prevalence of Toxocara infections, indicating the frequent soil contamination by this agent.

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.

A comparative study of congenital toxoplasmosis between public and private hospitals from Uberlândia, MG, Brazil

The main purpose of the present study was to examine if there is difference in terms of incidence rates of congenital toxoplasmosis among populations assisted in public and private hospitals from Uberlândia, state of Minas Gerais, Brazil. A total of 805 serum samples from cord blood were collected, being 500 from public hospital and 305 from private hospital, and all patients answered a questionnaire about pregnancy and newborns. An indirect enzyme linked immunosorbent assay (ELISA) was performed to detect IgG antibodies to Toxoplasma gondii and the positive samples were retested to verify the presence of specific IgM and IgA antibodies in a capture ELISA. We found significant differences among data from both hospitals with respect to maternal age, origin city, gestational age, number of visits to physicians during pregnancy, type of delivery, and birth weight. Seroprevalence of IgG antibodies against T. gondii for patients from public and private hospitals was 57.6% and 41.9% respectively, and this difference was statistically significant (P < 0.0001). In addition, the frequency of congenital toxoplasmosis measured by the presence of IgM and/or IgA antibodies toward T. gondii was exclusively located in samples from public hospital (0.8%), and no positive sample was seen in private hospital (0%). Considering that almost all babies suffering from congenital toxoplasmosis, if undiagnosed and untreated, will develop visual or neurological impairments by adulthood, the results presented herein emphasized the importance to accomplish screening programs for toxoplasmosis during pregnancy, particularly in the public hospitals, due to the expressive rate of congenital disease showed in the patients attended at these centers.

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.

Study of hantavirus infection in captive breed colonies of wild rodents

Wild sigmondontine rodents are known to be the reservoir of several serotypes of New World hantaviruses. The mechanism of viral transmission is by aerosol inhalation of the excreta from infected rodents. Considering that the captive breed colonies of various wild mammals may present a potencial risk for hantaviral transmission, we examined 85 speciemens of Thrichomys spp. (Echimyidae) and 17 speciemens of Nectomys squamipes (Sigmodontinae) from our colony for the presence of hantavirus infections. Blood samples were assayed for the presence of antibodies to Andes nucleocapsid antigen using enzyme-linked immunosorbent assay (ELISA). Additionally, serum samples from workers previously exposed to wild rodents, in the laboratories where the study was conducted, were also tested by ELISA to investigate prevalence of anti-hantavirus IgG antibodies. All blood samples were negative for hantavirus antibodies. Although these results suggest that those rodent's colonies are hantavirus free, the work emphasizes the need for hantavirus serological monitoring in wild colonized rodents and secure handling potentially infected rodents as important biosafety measures.

Molecular characterization of human T-cell lymphotropic virus coinfecting human immunodeficiency virus 1 infected patients in the Amazon region of Brazil

The present work evaluated the epidemiology of human immunodeficiency virus 1/human T-cell lymphotropic virus (HIV-1/HTLV) coinfection in patients living in Belém (state of Pará) and Macapá (state of Amapá), two cities located in the Amazon region of Brazil. A total of 169 blood samples were collected. The sera were tested by enzyme-linked immunosorbent assay to determine the presence of antibodies anti-HTLV-1/2. Confirmation of infection and discrimination of HTLV types and subtypes was performed using a nested polymerase chain reaction targeting the pX and 5' LTR regions, followed by restriction fragment length polymorphism and sequencing analysis. The presence of anti-HTLV1/2 was detected in six patients from Belém. The amplification of the pX region followed by RFLP analysis, demonstrated the presence of HTLV-1 and HTLV-2 infections among two and four patients, respectively. Sequencing HTLV-1 5' LTR indicated that the virus is a member of the Cosmopolitan Group, Transcontinental subgroup. HTLV-2 strains isolated revealed a molecular profile of subtype HTLV-2c. These results are a reflex of the epidemiological features of HIV-1/HTLV-1/2 coinfection in the North region of Brazil, which is distinct from other Brazilian regions, as reported by previous studies.

Use of the paired samples (cerebrospinal fluid and serum) in immunodiagnostic of active and inactive human neurocysticercosis

Paired samples of cerebrospinal fluid (CSF) and serum of 30 patients - 10 with active, 10 with inactive neurocysticercosis (NCC), and 10 control subjects - were evaluated by enzyme-linked immunosorbent assay (ELISA) using two Taenia crassiceps metacestode extracts as antigen in order to detect IgG antibodies. In active NCC, high levels of IgG were detected (p < 0.05). The CSF samples showed 80% (CI 72-88) of reactivity in the saline extract (S) and 90% (CI 84-95) in sodium dodecyl sulphate (SDS) and the serum samples were reactive in 90% (CI 84-95) and 100% (CI 98-100) in the S and SDS antigenic extracts, respectively. The use of the paired samples of CSF and serum in active NCC showed equivalent results suggesting that the serum samples could be used as a screening in those patients whose CSF puncture is counter-indicated.

Prevalence and risk factors of hepatitis C virus infection in hemodialysis patients from one center in Recife, Brazil

A hemodialysis population from a dialysis unit in the city of Recife, Northeastern Brazil, was screened to assess the prevalence of hepatitis C virus (HCV) infection and to investigate the associated risk factors. Hemodialysis patients (n = 250) were interviewed and serum samples tested for anti-HCV antibodies by enzyme-linked immunosorbent assay (ELISA). All samples were also tested for HCV RNA by reverse transcriptase nested polymerase chain reaction (RT-nested-PCR). Out of 250 patients, 21 (8.4%) were found to be seropositive by ELISA, and 19 (7.6%) patients were HCV RNA positive. HCV viraemia was present in 90.5% of the anti-HCV positive patients. The predominant genotype was HCV 1a (8/19), followed by 3a (7/19), and 1b (4/19). None of the anti-HCV negative patients were shown to be viraemic by the PCR. Univariate analysis of risk factors showed that time spent on hemodialysis, the number of blood transfusions and a blood transfusion before November 1993 were associated with HCV positivity. However, multivariate analysis revealed that blood transfusions before November 1993 were significantly associated with HCV infection in this population. Low prevalence levels were encountered in this center, however prospective studies are necessary to confirm these findings.

Predominance of Trypanosoma rangeli infection in children from a Chagas disease endemic area in the west-shore of the Panama canal

A total of 206 serum samples from children (3-14 years old) living in the Amador County (La Chorrera District, Province of Panama) were screened by indirect immunofluorescence antibody test (IFAT) for the presence of antibodies against Trypanosoma cruzi. Positive sera were confirmed by recombinant enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. The presence of blood trypanosomes was investigated by hemoculture and subsequently identify by a duplex polymerase chain reaction (PCR) followed by dot blot hybridization. The results indicated a prevalence of 9.7% for trypanosome infections, a seroprevalence of 2.9% against T. cruzi and a predominance of T. rangeli infection (6.8%). The immunological and clinical implications of these findings are discussed.

Evaluation of the natural killer cytotoxicity and the levels of cytokines in rats with type I diabetes mellitus

Type I diabetes mellitus (insulin-dependent DM = IDDM) is a chronic disease characterized by specific destruction of pancreatic beta cells, resulting in an absolute lack of insulin. Immune mechanisms, genetic susceptibility, and environmental factors are all implicated in the pathogenesis of Type 1 diabetes. This study was aimed at determining the efficiency of cytokines, natural killer (NK) cells in the pathophysiology of IDDM. Therefore, we evaluated the plasma levels of cytokines by specific enzyme-linked immunosorbent assay (ELISA) and the cytotoxicity activity of NK cells by anti-candididal index in rats with type I diabetes. We found that the cytotoxicity activity of NK cells in IDDM groups significantly decreased compared to the control groups. The levels of interferon-g (IFN-g) in IDDM groups were slightly higher than in healthy controls. These results indicate that the changes of T H1 type cytokines such as IFN-g and NK cell activity can play a role in the etiology of IDDM. The data may provide new strategies for the treatment of IDDM.