A Field Trial of Alternative Targeted Screening Strategies for Chagas Disease in Arequipa, Peru

In the wake of emerging T. cruzi infection in children of periurban Arequipa, Peru, we conducted a prospective field trial to evaluate alternative targeted screening strategies for Chagas disease across the city. Using insect vector data that is routinely collected during Ministry of Health insecticide application campaigns in 3 periurban districts of Arequipa, we separated into 4 categories those households with 1) infected vectors; 2) high vector densities; 3) low vector densities; and 4) no vectors. Residents of all infected-vector households and a random sample of those in the other 3 categories were invited for serological screening for T. cruzi infection. Subsequently, all residents of households within a 15-meter radius of detected seropositive individuals were invited to be screened in a ring case-detection scheme. Of 923 participants, 21 (2.28%) were seropositive. There were no significant differences in prevalence across the 4 screening strategies, indicating that household entomologic factors alone could not predict the risk of infection. Indeed, the most predictive variable of infection was the number of years a person lived in a location with triatomine insects. Therefore, a simple residence history questionnaire may be a useful screening tool in large, diverse urban environments with emerging Chagas disease

Patrones de coloración en la inmunofluorescencia indirecta y su utilidad en el diagnóstico de Leishmaniasis tegumentaria y enfermedad de Chagas

Objective: To determine the value of indirect immunofluorescence (IFI) in the diagnosis of leishmaniasis and Chagas disease. Material and method: Indirect immunofluorescence (IFI) was employed for diagnosing leishmaniasis and Chagas disease using Trypanosoma cruzi epimastigota as substrate antigens. A nuclear fluorescence pattern was found in sera from patients with leishmaniasis, and a peripheral pattern was found in those with Chagas disease. Afterwards, we estimated the diagnostic value of IFI for both diseases in a blinded fashion. Results: For diagnosing leishmaniasis, IFI sensitivity was 84.2%, specificity, 100%, positive predictive value, 100%, negative predictive value 82.9%, and accuracy was 91.0%. Conclusions: The immunofluorescence technique using Trypanosoma cruzi epimastigota, considering the proposed color patterns, is useful for diagnosing cutaneous leishmaniasis and T. cruzi infection by avoiding confusion because of immune cross-reactivity between these conditions.Objetivo: Determinar el valor diagnóstico de la Inmunofluorescencia indirecta (IFI) en el diagnóstico de leishmaniasis y enfermedad de Chagas. Material y método: La inmunofluorescencia indirecta (IFI) fue aplicada para el diagnóstico de leishmaniasis y la enfermedad de Chagas utilizando como sustrato antigénico epimastigotos de Trypanosoma cruzi. Se descubrió un patrón de fluorescencia nuclear con los sueros de pacientes con leishmaniasis y un patrón periférico para con los de la enfermedad de Chagas. Luego, en un estudio ciego, se estimó el valor diagnóstico de la IFI en ambas enfermedades. Resultados: En el diagnóstico de Leishmaniasis se encontró: Sensibilidad: 84,2%, especificidad: 100%, valor predictivo positivo: 100%, valor predictivo negativo: 82,9% y exactitud: 91,0%. Conclusiones: la técnica de Inmunofluorescencia utilizando epimastigotos de Trypanosoma cruzi y considerando los patrones de coloración propuestos, tiene utilidad en el diagnóstico de leishmaniasis tegumentaria y también en el diagnóstico de la infección chagásica evitando la confusión dada por la reacción inmune cruzada de estas enfermedades

Seroprevalencia de la infección por Trypanosoma cruzi y factores asociados en población adulta en una zona de alta endemicidad de Arequipa, Perú

Objective: determine the seroprevalence of infection by T. cruzi in the population above age 15 in the valley of Vítor, describing general characteristics and the presence of associated factors. Materials and Methods: 499 people above age 15 were randomly selected; epidemiological information was obtained through a survey. The diagnosis of the disease was made by ELISA and IIF. Results: the seroprevalence for Chagas reactivity was 10,2%, 10,35% in women and 10,0% in men. The median of age of the "typical" Chagas disease patient was 42±17,9, his/her time of residence in Vítor was 34±15,9 years; 51,0% had been born in the valley of Vítor. Agricultural workers made up 41,2%, of the general population, and 51,0% have a high school education. Rustic housing materials were associated with the infection. Conclusions: the valley of Vítor is an endemic area for Chagas disease. The infection equally affects men and women. The "typical" infected patient is native to the valley of Vítor, works in agriculture and has secondary level education. Rustic building materials is associated to the infection by T.cruzi because it favors the presence of the vector.Objetivo: determinar la seroprevalencia de infección por T. cruzi en pobladores mayores de 15 años del valle de Vítor, describiendo características generales y presencia de factores asociados a la infección. Material y Métodos: se seleccionaron aleatoriamente a 499 personas mayores de 15 años de edad, mediante encuesta se obtuvo la respectiva información epidemiológica. El diagnóstico serológico de la enfermedad se realizó mediante ELISA e IFI. Resultados: la seroprevalencia fue de 10,22%. En mujeres 10,35% y varones 10,04%. La mediana de edad del paciente chagásico fue de 42±17,86 años el tiempo de residencia fue de 34±15,95 años. El 50,98% es natural del valle de Vítor. Según la ocupación de la población general, agricultor 41,18%, ama de casa 31,37%. El 50,98% tiene instrucción secundaria. El único factor asociado a la infección fue el material rústico de las vivienda. Conclusion: el valle de Vítor es zona chagásica endémica. La infección afecta tanto a hombres como a mujeres. El poblador infectado es natural del valle de Vítor, se dedica a la agricultura y tiene secundaria como grado de instrucción. El material rústico de las viviendas se asocia a la infección por T.cruzi al favorecer la presencia del vector

Prevalencia de la enfermedad de Chagas en puérperas y transmisión congénita en una zona endémica del Perú The prevalence of Chagas' disease in puerperal women and congenital transmission in an endemic area of Peru

OBJETIVOS: Determinar la prevalencia de anticuerpos contra Trypanosoma cruzi en puérperas y la posible transmisión congénita de la enfermedad de Chagas en Arequipa, Perú, una zona donde esta enfermedad es endémica. MÉTODOS: Se estudió a las puérperas que dieron a luz entre diciembre de 2001 y julio de 2002 en tres hospitales (dos urbanos y uno rural) y cuatro centros de salud (tres rurales y uno urbano) del departamento de Arequipa, Perú. El estudio serológico comprendió el tamizaje de todas las puérperas para detectar anticuerpos contra T. cruzi mediante inmunofluorescencia indirecta (IFI); la prueba de inmunoadsorción enzimática (ELISA) y la titulación de anticuerpos IgG por IFI se usaron como pruebas confirmatorias. A las puérperas con seropositividad y a sus recién nacidos se les realizó la prueba de detección de anticuerpos IgM mediante IFI y se evaluó la presencia de infección mediante xenodiagnóstico (evaluada a los 30 y 60 días) y el micrométodo de Freilij. Los resultados se analizaron según la presencia del vector y de casos de enfermedad de Chagas en los lugares de nacimiento y de residencia de las puérperas. Dos neonatólogos evaluaron clínicamente a los recién nacidos para detectar anomalías y signos de enfermedad de Chagas congénita. RESULTADOS: La prevalencia general de enfermedad de Chagas en las 3 000 puérperas estudiadas fue de 0,73%; fue mayor en dos centros de salud ubicados en zonas rurales (2,2% en El Pedregal y 4,1% en La Joya) (P = 0,018) y la enfermedad estuvo asociada con el contacto directo previo con el vector (P OBJECTIVES: To determine the prevalence of antibodies against Trypanosoma cruzi in puerperal women and to assess possible congenital transmission of Chagas' disease in the department of Arequipa, Peru, where the disease is endemic. METHODS: Women who had given birth between December 2001 and July 2002 in three hospitals (two urban and one rural) and four health centers (three rural and one urban) of the department of Arequipa, Peru, were studied. The serological study included screening all the puerperal women in order to detect antibodies against T. cruzi through indirect immunofluorescence (IIF), with confirmatory testing done with enzyme-linked immunosorbent assay (ELISA) testing and the titration of immunoglobulin G (IgG) antibodies by IIF. IIF tests to screen for immunoglobulin M (IgM) antibodies were done with the seropositive women and their newborns, and infection was evaluated through xenodiagnosis (evaluated at 30 and 60 days) and the direct micromethod of Freilij et al. The results were analyzed in terms of the presence of the vector and of cases of Chagas' disease in the places where the puerperal women had been born and where they were living. Two neonatologists clinically evaluated the newborns in order to detect abnormalities and signs of congenital Chagas' disease. RESULTS: The overall prevalence of Chagas' disease in the 3 000 puerperal women studied was 0.73%. Prevalence was highest in two health centers located in rural areas (2.2% in El Pedregal and 4.1% in La Joya) (P = 0.018). The disease was associated with previous direct contact with the vector (P < 0.05) and with having been born in an area considered endemic (P < 0.01). Four (20%) of the 20 seropositive puerperal women were also positive by xenodiagnosis. However, none of the women was aware of her infectious carrier state, and none showed the characteristic symptoms or signs of acute or chronic Chagas' disease. IgM antibodies were not detected in any of the puerperal women. One neonate (whose mother did not have evidence of parasitemia) presented an IgM titer of 1/8, but in later controls neither IgM nor IgG antibodies were detected. Parasites were not detected in the blood of the neonates by either of the two testing methods used. Of the 20 neonates evaluated, one presented microcephaly and hepatosplenomegaly; although the child had specific IgG antibodies against T. cruzi at birth, the antibodies were not present at the age of two months. The growth and development of the other 19 newborns were normal. CONCLUSIONS: The prevalence of Chagas' disease in puerperal women of the department of Arequipa, Peru, is low. No cases of intrauterine congenital transmission were found. We recommend carrying out studies on prenatal detection that evaluate more mothers and in which women who give birth at home also participate

Comparison of targeted strategies to detect <i>T. cruzi</i>-infected individuals in 18 periurban communities, Arequipa, Peru.

1<p>Originally 81 houses had <i>T.cruzi</i>-infected triatomines, however 1 house was no longer inhabited at the time of this study.</p>2<p>27 additional households within 15 meters of an index human infection had already been approached under the previous strategies.</p>3<p>Number of participating households out of total households invited to participate.</p>4<p>Percent of household members participating of total household members >1 year old.</p

Flowchart of household selection into targeted screening strategies for Chagas disease based on vector-control data.

<p><a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001468#pntd-0001468-g001" target="_blank">Figure 1</a> displays the scheme used to stratify households into 4 targeted strategies to screen household members for human <i>T. cruzi</i> infection. The stratification was based on Ministry of Health (MOH) entomologic data from recent spray campaigns and laboratory analysis in the city of Arequipa, Peru. ¹ Although 81 households had <i>T.cruzi</i>-infected <i>T.infestans</i> at the time of spray, 1 household was no longer inhabited at the time of this study, and 2 refused to participate.</p

Univariate Poisson regressions¹ on <i>T. cruzi</i> infection among targeted screening participants in Arequipa, Peru.

1<p>Poisson regressions included a random effect term to control for correlation among participants from the same household.</p>2<p>Univariate analysis of education includes only adults (age 18 or over).</p>3<p>The lifetime total number of places in which each participant had lived was tabulated from the migration histories, as were each participants' total number of years lived in a rural, periurban or urban location, and in a location recalled as being infested with <i>T. infestans</i>.</p