Gilberto Avalos

Triatomines Involved in Domestic and Wild Trypanosoma cruzi Transmission in Concepción, Corrientes, Argentina

An entomological and serological survey was performed in three localities of the Department of Concepción, Province of Corrientes, Argentina in 1998 and 1999, to identify triatomines species involved in domestic and wild transmission of Chagas disease. Triatomines were collected by man/hour capture in 32 houses randomly selected and 44 nearby outdoor ecotopes. Trypanosoma cruzi infection in triatomines was assessed by direct microscopic observation (400x) of feces and polymerase chain reaction. Serological techniques used for people were Indirect Hemagglutination Test and Indirect Fluorescent Test. Triatomines were collected in 28.1% of the houses and 31.8% of the wild biotopes. Triatoma infestans (Klug 1834) was exclusively found indoors and T. cruzi infected 60% of them. Triatoma sordida (Stål 1859) was mainly found in extradomestic ecotopes where trypanosome infection rate reached 12.7%. Serological study of 98 local people showed that 29.6% were seroreactive; most of their houses were closed to wild biotopes colonized by T. sordida. Results indicate that there is an active T. infestans mediated transmission of Chagas disease in this zone that yields important human prevalence and that the populations of T. sordida in wild biotopes not only sustain the wild T. cruzi cycle but also represent an actual risk for people living in the area.

Household infestation by triatomines and human seroprevalence in Empedrado Department, Corrientes, Argentina

Domestic and peridomestic triatomine colonization, T. infestans infection rate and human seropositives to Trypanosoma cruzi in rural areas of Empedrado Department, Corrientes, Argentina, were carried out. Methods used in order to search the triatomines, to determine them systematically, to obtain their infection rates and the human seropositives, were the same applied in a previous report. From 100 households characterized, 53.0% had mud walls, laminated zinc or cardboard combined with other elements were used in 37.5% of the roofs, and 83.0% had earthen floors. Presence of domestic animais sleeping inside houses was detected in 91.0% of human dwellings. Domestic infestation by T. infestans was 29.0% and 1.0% by T. sordida. Other T. infestans entomological indexes recorded were: natural infection index = 23, colonization index = 75 and dispersion index = 54,5. T. sordida was found in 12.1% of peridomestic structures while T. infestans was detected in 2.4%. General prevalence from 298 human sera analized by Indirect Hemagglutination and Indirect Immunofluorescence Antibody Tests, was 32.2%. A high percentage of positive serology (23.7%) was found among 0-10 years old, wich represent the age group of higher transmission risk.

Infestacion domestica por triatoma infestans y prevalencia de seropositivos al Trypanosoma cruzi en un area rural del nordeste argentino

An epidemiological study was carried out from April 1991 to December 1993 to obtain a general view of T. cruzi domestic transmission in rural areas of San Miguei Department, Corrientes. From 100 analyzed households, 50.0% was infested by T infestans (Klug, 1834) and 1.0% by T. sordida (Stal, 1859). Domiciliary colonization by T. sordida is reported for first time in Corrientes province. T. cruzi infection of T. infestans was 23.1%. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of anti T. cruzi antibodies in 388 human sera, 23.4% showed serological reactivity. An important high rate (12.9%) was observed in the age group of higher transmission risk. Seropositives percentages increased with age and reached 50.0% in 31-40 years old group. Domestic infestation by T. infestans, seropositive human prevalence to T. cruzi and householders precarious life conditions prove that this endemic disease is still a problem in the studied area.

Interactions Between Triatoma infestans and Triatoma sordida (Hemiptera: Reduviidae) in Artificial Ecotopes: Population Growth and Age Structure

Abstract Interaction characteristics between Triatoma infestans Klug, 1834 and Triatoma sordida Stål, 1859 populations were studied in artificial ecotopes for 16 mo. The experimental design involved simultaneous treatments with T. infestans and T. sordida together in the same experimental unit (EU) and each separately in two control units (CU) made of adobe bricks. Chickens were used as host animals. Each unit was dismantled monthly to estimate triatomine population size and age structure, rebuilt, and repopulated with the same insects. In both units, T. infestans population growth followed a logistic model, whereas T. sordida did not show this pattern. T. infestans completed a generation in 24 wk (EU) and 32 wk (CU1), whereas T. sordida did not complete one generation during this period. We concluded that T. infestans showed a better colonizing success than T. sordida. After living together for 1 yr, an interference process took place that resulted in the extinction of T. sordida.

First description of the male of Oonops nigromaculatus Mello-Leitão, 1944 (Araneae: Oonopidae) with the redescription of the female and new records

The male of Oonops nigromaculatus Mello-Leitao 1944 is described for the first time and the female is redescribed from recently collected specimens. New records from Argentina and Uruguay are provided.