Behavioural biology of Chagas disease vectors

Many arthropod species have adopted vertebrate blood as their main food source. Blood is rich in nutrients and, except for the presence of parasites, sterile. However, this food source is not freely available, nor is obtaining it devoid of risk. It circulates inside vessels hidden underneath the skin of mobile hosts that are able to defend themselves and even predate the insects that try to feed on them. Thus, the haematophagous lifestyle is associated with major morphological, physiological and behavioural adaptations that have accumulated throughout the evolutionary history of the various lineages of blood-sucking arthropods. These adaptations have significant consequences for the evolution of parasites as well as for the epidemiology of vector-transmitted diseases. In this review article, we analyse various aspects of the behaviour of triatomine bugs to illustrate how each behavioural trait represents a particular adaptation to their close association with their hosts, which may easily turn into predators. Our aim is to offer to the reader an up-to-date integrative perspective on the behaviour of Chagas disease vectors and to propose new research avenues to encourage both young and experienced colleagues to explore this aspect of triatomine biology.

Feeding behavior of Triatoma vitticeps (Reduviidae: Triatominae) in the state of Minas Gerais, Brazil

The objective of this study was to evaluate the feeding behavior of Triatoma vitticeps through the identification of its food sources and the characterization of the blood ingestion process. In addition, we aimed to verify if the saliva of this vector interferes with the perception of the host during the feedings by creating a nervous impulse. Here, we demonstrated that the T. vitticeps saliva reduces, gradually and irreversibly, the amplitude of the compound action potential of the nervous fibre, which helps decrease the perception of the insect by the host. The precipitin reaction demonstrated the feeding eclecticism of this vector, with the identification of eight food sources - most of them found simultaneously in the same insect. The analysis of the electrical signals produced by the cibarial pump during meals demonstrated that the best feeding performance of T. vitticeps nymphs that fed on pigeons is mainly due to the higher contraction frequency of the pump. The longer contact period with the host to obtain a complete meal compared with other triatominae species of the same instar could favor the occurrence of multiple blood sources in T. vitticeps under natural conditions, as it was evidenced by the precipitin test.

Potencial biológico do Triatoma brasiliensis / Biological potential of Triatoma brasiliensis

Foram estudados alguns parâmetros biológicos e fisiológicos do Triatoma brasiliensis em comparaçäo com o Triatoma infestans e com o Triatoma pseudomaculata. O T. brasiliensis, alimentado em camundongos, apresentou um ciclo evolutivo de ninfa de primeiro estádio a adulto mais rápido e uma fecundidade maior quando comparado às demais espécies. O T. infestans apresentou a maior velocidade de ingestäo sangüínea nos dois hospedeiros testados, seguido pelo T. brasiliensis e pelo T. pseudomaculata. Os testes de coagulaçäo nos quais foram utilizados extratos de glândulas salivares de T. brasiliensis apresentaram valores de atividade anti-coagulante intermediários entre os de T. infestans e os de T. pseudomaculata.