Chagas disease: national survey of seroprevalence in children under five years of age conducted in 2008.

BACKGROUND: Since the early 1990s, programs to control Chagas disease in South America have focused on eradicating domiciliary Triatoma infestans, the main vector. Seroprevalence studies of the chagasic infection are included as part of the vector control programs; they are essential to assess the impact of vector control measures and to monitor the prevention of vector transmission. OBJECTIVE: To assess the interruption of domiciliary vector transmission of Chagas disease by T. infestans in Paraguay by evaluating the current state of transmission in rural areas. METHODS: A survey of seroprevalence of Chagas disease was carried out in a representative sample group of Paraguayans aged one to five years living in rural areas of Paraguay in 2008. Blood samples collected on filter paper from 12,776 children were tested using an enzyme-linked immunosorbent assay. Children whose serology was positive or undetermined (n = 41) were recalled to donate a whole blood sample for retesting. Their homes were inspected for current triatomine infestation. Blood samples from their respective mothers were also collected and tested to check possible transmission of the disease by a congenital route. FINDINGS: A seroprevalence rate of 0.24% for Trypanosoma cruzi infection was detected in children under five years of age among the country's rural population. Our findings indicate that T. cruzi was transmitted to these children vertically. The total number of infected children, aged one to five years living in these departments, was estimated at 1,691 cases with an annual incidence of congenital transmission of 338 cases per year. MAIN CONCLUSION: We determined the impact of vector control in the transmission of T. cruzi, following uninterrupted vector control measures employed since 1999 in contiguous T. infestans-endemic areas of Paraguay, and this allowed us to estimate the degree of risk of congenital transmission in the country.

Chagas disease: national survey of seroprevalence in children under five years of age conducted in 2008

BACKGROUND Since the early 1990s, programs to control Chagas disease in South America have focused on eradicating domiciliary Triatoma infestans, the main vector. Seroprevalence studies of the chagasic infection are included as part of the vector control programs; they are essential to assess the impact of vector control measures and to monitor the prevention of vector transmission. OBJECTIVE To assess the interruption of domiciliary vector transmission of Chagas disease by T. infestans in Paraguay by evaluating the current state of transmission in rural areas. METHODS A survey of seroprevalence of Chagas disease was carried out in a representative sample group of Paraguayans aged one to five years living in rural areas of Paraguay in 2008. Blood samples collected on filter paper from 12,776 children were tested using an enzyme-linked immunosorbent assay. Children whose serology was positive or undetermined (n = 41) were recalled to donate a whole blood sample for retesting. Their homes were inspected for current triatomine infestation. Blood samples from their respective mothers were also collected and tested to check possible transmission of the disease by a congenital route. FINDINGS A seroprevalence rate of 0.24% for Trypanosoma cruzi infection was detected in children under five years of age among the country’s rural population. Our findings indicate that T. cruzi was transmitted to these children vertically. The total number of infected children, aged one to five years living in these departments, was estimated at 1,691 cases with an annual incidence of congenital transmission of 338 cases per year. MAIN CONCLUSION We determined the impact of vector control in the transmission of T. cruzi, following uninterrupted vector control measures employed since 1999 in contiguous T. infestans-endemic areas of Paraguay, and this allowed us to estimate the degree of risk of congenital transmission in the country.

Correlation between normalized difference vegetation index and malaria in a subtropical rain forest undergoing rapid anthropogenic alteration.

Time-series of coarse-resolution greenness values derived through remote sensing have been used as a surrogate environmental variable to help monitor and predict occurrences of a number of vector-borne and zoonotic diseases, including malaria. Often, relationships between a remotely-sensed index of greenness, e.g. the normalized difference vegetation index (NDVI), and disease occurrence are established using temporal correlation analysis. However, the strength of these correlations can vary depending on type and change of land cover during the period of record as well as inter-annual variations in the climate drivers (precipitation, temperature) that control the NDVI values. In this paper, the correlation between a long (260 months) time-series of monthly disease case rates and NDVI values derived from the Global Inventory Modeling and Mapping Studies (GIMMS) data set were analysed for two departments (administrative units) located in the Atlantic Forest biome of eastern Paraguay. Each of these departments has undergone extensive deforestation during the period of record and our analysis considers the effect on correlation of active versus quiescent periods of case occurrence against a background of changing land cover. Our results show that timeseries data, smoothed using the Fourier Transform tool, showed the best correlation. A moving window analysis suggests that four years is the optimum time frame for correlating these values, and the strength of correlation depends on whether it is an active or a quiescent period. Finally, a spatial analysis of our data shows that areas where land cover has changed, particularly from forest to non-forest, are well correlated with malaria case rates.

Phlebotominae sand flies in Paraguay: abundance distribution in the Southeastern region.

From September 1993 to August 2001, 7,190 phlebotomine were collected with CDC light trap in an endemic area for human leishmaniasis, in the departments of Misiones and Itap a, Paraguay. Eleven species were identified: Lutzomyia neivai (93.7%), L. whitmani (4.1%), and L. fischeri, L. shannoni, L. migonei, L. misionensis, L. cortelezzii, L. pessoai, L. alphabetica, Brumptomyia avellari and B. guimaraesi (less than 1%). The last three species are new records for the country. The biodiversity and phlebotomine abundance were associated with the proximity to primary forest or gallery forest, but L. neivai was also found in peridomestic periurban environment. L. neivai was found throughout the year, and showed a period of higher activity from September to April (spring to fall) with a unimodal or bimodal pattern in relation to the annual rainy peaks during the summer. Background literature about phlebotomine from Paraguay has been reviewed.

Phlebotominae sand flies in Paraguay. Abundance distribution in the Southeastern region

From September 1993 to August 2001, 7,190 phlebotomine were collected with CDC light trap in an endemic area for human leishmaniasis, in the departments of Misiones and Itapúa, Paraguay. Eleven species were identified: Lutzomyia neivai (93.7 percent), L. whitmani (4.1 percent), and L. fischeri, L. shannoni, L. migonei, L. misionensis, L. cortelezzii, L. pessoai, L. alphabetica, Brumptomyia avellari and B. guimaraesi (less than 1 percent). The last three species are new records for the country. The biodiversity and phlebotomine abundance were associated with the proximity to primary forest or gallery forest, but L. neivai was also found in peridomestic periurban environment. L. neivai was found throughout the year, and showed a period of higher activity from September to April (spring to fall) with a unimodal or bimodal pattern in relation to the annual rainy peaks during the summer. Background literature about phlebotomine from Paraguay has been reviewed

Fuente de alimentocion de Triatominos domesticos (Hemiptera-Reduvidae) en una localidad endemica para la enfermedad de Chagas / Annual Reports 1997 / Feeding sources of domestic Triatomines (Hemiptera-Reduviidea) in a endemic locality for Chagas Disease

Para analizar el cotenido sanguíneo original de triatominos que se habían alimentado de diferntes hospederos se utilizó la prueba de doble difusión en agar. Se procedió a la extracción del contenido intestinal de 223 Triatoma infestans y 23 Triatoma sordida, colectados tantos en dormitorios como en el peridomicilio (cosina, gallineros) de las vivindas habitadas de la localidad de Cerro Guy, endémica para la enfermedad de Chagas. Para realizar el perfil alimentarios de los vectores se utilizaron siete antisueros específicos; anti-humano; anti-perro; anti-gato; anti-pollo; anti-cabra; anti-rata, y anti-cabayo. Se utilizaron restos de sangre (antígeno problema) extraído de adultos y ninfas de 2º a 5º estadío evolutivo. Por la reacción de precipitina positiva se comprobó que las tres fuentes de alimentación más frecuentes fueron ave de corral (50,2 por ciento), humano (14,7 por ciento), y perro (5,3 por ciento) y en muchos casos se detectó de una fuentede alimentación. Casos con resultados negativos tambíen fuero observados, probablemente debido aque los anticuerpos especificos a los animales donantes no fueron incluidos en la batería de los 7 antisueros empleados, o contenido intestinal insuficientes de muchos adultos, o un prolongado ayuno del insecto. Cerro Guy se encuentra en proceso de reinfesteción, que se mantiene a nivel peridomiciliar por el pollo (gallus domesticus) como fue alimentaria predominante. Si bien el índice de infeción fue bajo (2,8 por ciento) todos los ejemplares positivos correspondieron a T.infestans, vecto principal de la enfermedad de Chagas en el cono sur. Este estudio es importante para establecer la relación del vector con su fuentes de nutrición y el mantenimiento de la dinámica de transmisión del paràsito. Además contribuye a clarificar el panorama epidemiológicos de la enfermedad, en especial el papel que juega la fuente alimentaria en el proceso de reinfestación de la comunidad