The migration of invasive vector species has contributed to the worldwide extension of infectious diseases such as dengue (Aedes aegypti) and chikungunya (Aedes albopictus). It is probably a similar behaviour for certain vectors of Chagas disease which allowed it to become a continental burden in Latin America. One of them, Triatoma rubrofasciata has also been spreading throughout the tropical and subtropical world. Here, the recent and massive peridomestic presence of T. rubrofasciata in Vietnam cities is reported, and tentatively explained, highlighting the need for improved entomological surveillance.

A tripanossomíase por Trypanosoma cruzi na Região Amazônica tem sido motivo de preocupação ao longo dos tempos, dada a grande dispersão de vetores infectados e crescentes migrações humanas. Um seminário internacional da ECLAT em julho/2002 analisou a situação e perspectivas quanto à dispersão da doença humana concluindo ser a mesma ainda esporádica e com potencial de ampliação na área, requerendo objetivo e integrado esforço de vigilância, compartido por todos os Países da Região.

American Trypanosomiasis (Chagas' disease) due to Trypanosoma cruzi in the Amazon Region has become a target of scientific preoccupation in recent years because of the wide dispersion of infected vectors and intensive human migration into the region. An European Community and Latin America Triatominae Network international workshop held in July 2002 analyzed the general situation and the perspectives of human Chagas' disease in the area, concluding that although its occurrence remains sporadic, there is strong potential for the disease to spread, and a requirement for an integrated surveillance effort to be shared by all countries of the region.

Eye colour of Triatoma infestans is controlled at a single autosomal locus, with black-eye as the dominant gene and red-eye as the recessive. Inheritance of these characters follows a classical Mendelian system, enabling eye colour to be used as a marker for studies of mating frequency. We found no significant differences in oviposition rates and egg hatching rates irrespective of parental phenotypes. Different mating schedules between red-eye and black-eye parents showed that eye colour did not affect mating competence. Females mated with a single male or with different males together or in succession produced similar numbers of fertile eggs, with the eye colour of the offspring reflecting exposure to the different males. We conclude that although a single mating can provide sufficient sperm for the whole reproductive life of the female, multiple matings can result in balanced assortative sperm usage from the spermatheca.

No presente trabalho procurou-se constatar se a deltametrina em baixas doses produz excito-repelência em triatomíneos, conforme já observado para mosquitos. O experimento foi realizado utilizando-se uma caixa de madeira recoberta com tecido impregnado com deltametrina nas doses de 2,5 e 5mg ia/m². As espécies de triatomíneos estudadas foram o T. infestans, P. megistus, R. neglectus e T. sordida. Exemplares adultos eram liberados em um dos lados da caixa, e a posição dos mesmos era anotada em períodos subseqüentes. A experiência foi realizada no dia da impregnação do tecido, e repetida aos 30 e 60 dias para o T. sordida; aos 120 dias incluíram-se as demais espécies. Também foram observadas a mortalidade dos insetos e a tentativa de fuga da caixa através do vôo. A excito-repelência foi evidente para todas as espécies e doses até o 120º dia. A única espécie que voou foi o P. megistus. O efeito excito-repelente pode ser considerado uma vantagem adicional ao poder do inseticida pois dificultaria a instalação de novas colônias a partir de fêmeas que ingressassem nas casas através do vôo, além de promover o desalojamento de exemplares presentes nas frestas das paredes e outros esconderijos.

This work demonstrates that deltamethrin in low doses produces an excito-repellency effect on triatomines, as already observed for mosquitoes. A wooden box covered with a cloth impregnated with deltamethrin at doses of 2.5 and 5mg ai/m² was utilized for the experiment. The triatomine species studied were Triatoma infestans, Panstrongylus megistus, Rhodnius neglectus and Triatoma sordida. Adults were released in one of the sides of the box and their position was noted in subsequent periods. The observations were realized on the day the cloth was impregnated and subsequently repeated at 30 and 60 days for T. sordida; on day 120, the remaining species were included. Insect mortality and attempts at flight from the box were also observed. Excito-repellency was evident for all species and doses up to day 120. The only species that attempted to fly was P. megistus. The excito-repellency effect may be considered as an additional advantage to the insecticide power, as it should be able to prevent the installation of new colonies by females that fly into the homes, and at the moment of the spraying, it should promote the flushing out of triatomines from the wall crevices and from other shelters.

Among the triatomines considered as secondary in the epidemiology of Chagas disease, Rhodnius neglectus is frequently captured in artificial ecotopes, especially peridomiciliary ones, rarely producing colonies indoors. Nevertheless, the presence of breeding colonies in houses was unquestionably demonstrated in some areas of the State of Goiás, Brazil. Previous isoenzyme comparisons of this species with morphologically close triatomines, such as R. prolixus, R. robustus or R. nasutus, did not produce definitive conclusions because of doubt about the geographical origin of the R. neglectus. We present here, for the first time, the isoenzyme profile of topotypes of R. neglectus. In addition, wild caught specimens from the type locality, Uberaba (Minas Gerais, Brazil), were compared to wild caught specimens from Jaraguá (Goiás, Brazil), where R. neglectus is more frequently reported invading houses. We used isoenzyme, morphology and morphometry analysis. Neither morphological nor enzymatic differences were found between areas, but metric, size-related divergence was evidenced between them.

Integrando os objetivos principais da iniciativa dos 6 Países do Cone Sul para a eliminação da doença de Chagas, a partir de 1991, foram intensificadas as ações de controle das atividades hemoterápicas, em paralelo com o combate intensivo ao Triatoma infestans, principal vetor da doença da Região. Através das atividades específicas e também como produto direto do controle vetorial, nota-se importante diminuição dos riscos da transmissão transfusional do Trypanosoma cruzi nas áreas trabalhadas. Além de legislação específica sobre a qualidade da hemoterapia, implementaram-se laboratórios nacionais e regionais de referência, com a assistência da OPS, objetivando-se uma boa sorologia pré-transfusional dos doadores, cuja cobertura tem aumentado. Observa-se ainda uma progressiva diminuição na prevalência da infeção chagásica entre doadores e também um progressivo deslocamento dos doadores infetados para grupos etários mais elevados, como fruto do controle vetorial e do próprio descarte de doadores soro-positivos em doações anteriores. São analisados dados e tendências do problema pelos Países, sendo mais preocupante a situação da Bolívia, com maiores taxas de prevalência e menores de cobertura do programa, ali sendo indicadas ações de quimioprofilaxia, conforme os critérios da OMS. Antevê-se a médio prazo o controle da transmissão da doença de Chagas humana na maior parte da Região, desde que cumpridas corretamente as etapas do programa em andamento, devidamente consolidadas através de efetiva vigilância epidemiológica.

The Southern Cone Initiative against Chagas' disease, was launched in 1991. The aim was to interrupt the transmission of Chagas disease by elimination of domestic populations of the major vector, Triatoma infestans, and by improved screening of blood donors. As a result of these activities, a marked reduction in the risk of transfusional transmission can now be seen throughout the programme area. In addition to specific legislation concerning the quality of transfused blood, a series of national and regional reference laboratories have been set up with the help of PAHO in order to improve the quality of pre-transfusional serodiagnosis. Results indicate a progressive reduction in the overall infection prevalence of blood donors, and show that the age-prevalence curve has shifted towards older age-groups. In this paper we analyse the changes in infection prevalence in the Southern Cone countries, drawing attention to the situation in Bolivia which has the highest indices of infection and lowest levels of coverage by the control programme. In this situation chemoprofylaxis of blood prior to transfusion may be recommended in accordance with PAHO criteria. In the medium term however, interruption of human Chagas disease transmission may be expected over most of the Southern Cone region, as long as the control activities are continued and consolidated through effective epidemiological surveillance.