Taeniasis

BRIEF COMMUNICATION

SUMMARY

Serological survey was performed to detect IgG antibodies anti-Taenia solium metacestodes in blood donors of Hemocentro Regional de Uberlandia, Minas Gerais, Brazil. A total of 1133 sera from blood donors coming from four cities of TriAngulo Mineiro area were analyzed by the indirect fluorescence antibody test (IFAT) and the enzyme linked immunosorbent assay (ELISA). Specific IgG antibodies were found in 5.6% of the studied population, showing differences in the positive rates according to their origin: Araguari (13.5%), Tupaciguara (5.0%), Monte Alegre de Minas (4.8%) and Uberlandia (4.7%). The results indicate the probable endemicity of cysticercosis in this population.

KEYWORDS: Human cysticercosis; Blood donors; Seropositivity.

Taeniasis cysticercosis complex represent a serious problem for the public health in many parts of the world28 including Brazil14,27. In the areas where the infection is endemic, the transmission is clearly related to the poor personal hygiene and deficient environmental sanitation, specially in rural areas where swine are created in rustic manage conditions20.

It has been estimated by World Health Organization that 50 millions subjects are infected by the taeniasis/cysticercosis complex and 50,000 of them dye in every year5.

In Brazil, there are various studies on the frequency of cysticercosis in the human population. The majority of the reported cases are related to disease-cases restricted to the neurology and neurosurgery specialized centers or to anatomo-pathological materials coming from psychiatric and common hospitals, which show a high frequency in the states of Parana14, Sao Paulo3,26, Minas Gerais8,11,23 and Rio Janeiro18. However, the population prevalence is not known because of the absence of notification of the disease24.

The aim of this study was to determine the seropositivity of IgG antibodies anti-Taenia solium metacestodes in blood donors of Hemocentro Regional de Uberlandia. Uberlandia is enclosed in a microregion of the Triangulo Mineiro with 500,095 habitants, receiving immigrants from all adjacent cities since it is the convergence center of the entire TriAngulo Mineiro.

This study received approval from the Ethical Committee of Fundacao Hemominas, MG.

Serum samples were obtained from blood donors, during May and June 1995, and stored at -20 deg C. Sampling was calculated by using the Rodrigues' technique19, according to the formula: n = Z^sup 2^ x P x Q/d^sup 2^. The 99% confidence level and 1.4% observed value were considered as described by COSTA-CRUZ et al.8. Thus, the sampling size was 660, being augmented to 1133 sera obtained from subjects coming from four cities of Triangulo Mineiro area: Uberlandia (888), Tupaciguara (120), Araguari (104) and Monte Alegre de Minas (21).

Serological assays included the indirect immunofluorescence test (IFAT) by using particulate antigen of Cysticercus cellulosae15 and enzyme linked immunosorbent assay (ELISA) by using total saline extract of C. cellulosae7 to detect IgG antibodies anti-T solium metacestodes. The quantitative ELISA6 with modification was carried out using polystyrene microplates (Interlab, Sao Paulo, Brazil) and the reagents were assayed in 50 (mu)L/well. The plates were coated with saline extract at 10 (mu)g/mL in 0.06M carbonate-bicarbonate buffer, pH 9.6 and incubated overnight at 4 deg C. The plates were washed three times for 5 minutes with PBS containing 0.05% Tween 20 (PBS-T) and incubated with the serum samples, including three positive and three negative control sera, diluted at 1:200 in PBS-T for 45 minutes at 37 deg C. After new washing as previously described, the conjugate rabbit anti-human IgG (Fc chain specific) labeled with peroxidase (Sigma, USA) diluted at 1:2000 in PBS-T was added and incubated for 45 minutes at 37 deg C. After washing, the enzymatic substrate consisting of H^sub 2^O^sub 2^ (Merck, Germany) plus o-phenylenediamine (OPD) diluted in 0.1 M citrate-- Na^sub 2^HPO^sub 4^ buffer pH 5.5 was added. The reaction was stopped after 15 minutes with 20 (mu)L/well of 1M H^sub 2^SO^sub 4^ and the absorbance values were determined in an ELISA reader (Metrolab, Argentina) at 490 nm. The cut off was set using the mean absorbance values obtained from 3 non-- reactive sera plus two standard deviations. Serum samples were considered as reactive when presenting antibody titers in both IFAT (>= 20) and ELISA (>= 200) as well as when presenting antibody titers in either IFAT (>= 40) or ELISA (>= 400).

From 1133 studied subjects, 74.2% were male and 25.8% female, and the age ranged from 18 to 60 years. IgG antibodies anti-T solium metacestodes were found in 5.6% of the studied population, and the distribution of the frequencies of positivity according to their origin is demonstrated in Table 1. The mean age of the seropositive subjects was 33.5 years for male and 47.5 years for female. The general distribution of 1133 serum samples according to the antibody titers in MAT and ELISA is demonstrated in Table 2.

Considering ELISA as reference, the tests showed 1070/1082 (98.9%) co-negativity, 24/51 (47.0%) co-positivity and 96.6% concordant results.

The mean rate of 5.6% found for antibodies anti-T solium metacestodes in sera from blood donors of the four cities of Triangulo Mineiro area indicate the probable endemic character of cysticercosis in the region, since the Pan-American Health Organization16 sets the index of 0.1% as endemic for human cysticercosis. Necropsy data of subjects from this region demonstrated the mentioned endemic index8,11,13.

AGAPEJEV2 stated that the lethality caused by neurocysticercosis (NC) was 2.2%. Undoubtedly, NC is the responsible for the most of the obits, either by severity of the disease or by resulting of complications in the treatment.

In 1996, diagnostic criteria for cysticercosis, based on the objective evaluation of clinical, radiologic, immunologic and epidemiologic data were proposed9 and in 2001(10) a panel of experts agreed upon more accurate and stringent revised criteria for diagnosis of NC. Furthermore, serology of NC may be plagues with apparently false positive results for several reasons: some healthy subjects from endemic countries may have serum antibodies induced by previous infections that did not progress to the establishment of cysticerci, or because they bear cysticerci that are localized in clinically inconspicuous anatomic sites21. Also, a major cause of truly false positive serology in methods using whole or partially purified antigen preparations is the extensive sharing of antigen epitopes of many cestodes and helminths12.

ELISA standardized for crude antigens has been used in the diagnosis of human cysticercosis3,4,6,22 but due the frequency of cross-reaction observed in endemic areas, as well as to other helminthic infections, differences of sensibility and specificity have been found. In this work, the 1:200 dilution used in ELISA decrease cross-reaction indices in sera22. Despite the high specificity of the enzyme-linked immunoelectrotransfer blot assay (EITB) and glycoprotein antigens for diagnosing human cysticercosis25, cross reaction with other parasites may occur and the wide divergence in sensitivity of serological tests reflects differences not only in the methodology employed, but also in the characteristics of the population investigated3. ELISA and EITB together may supply reliable results for the diagnosis of human cysticercosis3,22, but EITB is too costly for application to populations of developing countries. Reports of the literature have reinforced the necessity in developing more reliable immunological methods to detect antibodies anti-metacestodes in serum or cerebrospinal fluid1,4,7,16,17.

According to OPAS16, the compulsory notification of cysticercosis is the best resource for the epidemiological investigation and comparative analysis of prevalence in the different locals. In addition, such notification permits the mapping of the local of patients' homes in order to better guide the prevention measures, however, although compulsory, the notification of cysticercosis is still underestimated. The results obtained in this work indicate the probable endemicity of cysticercosis in this population and aimed to contribute for a better knowledge of the infection in our region, alerting for the fact that control and prevention measures should be taken at primary level of assistance to health in the public services.

RESUMO

Anticorpos anti-formas metacestodeas de Taenia solium em amostras de soros de doadores de sangue de quatro cidades da regiao do Triangulo Mineiro, Minas Gerais, Brasil, 1995

Realizou-se pesquisa sorologica para detectar anticorpos IgG anti-- formas metacestodeas de Taenia solium em doadores de sangue do Hemocentro Regional de Uberlandia, Minas Gerais, Brasil. O total de 1133 amostras de soros de doadores de sangue de quatro cidades do Triangulo Mineiro foi analisado pelo teste de imunofluorescencia indireta (IFI) e o teste imunoenzimatico (ELISA). Anticorpos IgG especificos foram detectados em 5,6% da populacao estudada, mostrando diferencas nas taxas de positividade de acordo com suas cidades de origens: Araguari (13,5%), Tupaciguara (5,0%), Monte Alegre de Minas (4,8%) e Uberlandia (4,7%). Os resultados indicam a provavel endemicidade de cisticercose nesta populacao.

REFERENCES

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Received: 01 April 2002

Accepted: 03 June 2002

Elisangela de Paula SILVEIRA-LACERDA(1), Eleuza Rodrigues MACHADO(2), Silvio Cesar de Freitas ARANTES(1) & Julia Maria COSTA-CRUZ(2)

(1) Setor Sorologia, Hemocentro Regional de Uberlandia, Fundacao Hemominas, Uberlandia, MG, Brasil.

(2) Laboratorio de Parasitologia, Instituto de Ciencias Biomedicas da Universidade Federal de Uberlandia, MG, Brasil.

Correspondence to: Elisangela de Paula Silveira-Lacerda, Hemocentro Regional de Uberlandia, Fundacao Hemominas, Laboratorio de Ensino e Pesquisa, Av. Levino de Souza 1845, 38405-322 Uberlandia, MG, Brasil. Fax: +55.34.3222-8887. Email.: elisangelapaula@hotmail.com

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