DISCUSSION AND CONCLUSIONS
The "brasiliensis population" appears to be the most important chromatic pattern from the epidemiological point of view. Comparing specimens from the Herman Lent collection this pattern presents the most wide geographical distribution: Ceará, Paraíba, Piauí e Rio Grande do Norte; it was not observed simpatry among the different colour patterns (Costa et al. 1997b); the "brasiliensis population" have been captured naturally infected in wilderness and in peridomicile ecotopes; this pattern can also occurs indoors in Caicó (Fundação Nacional de Saúde - FNS pers. com.).
The "macromelasoma" and the "Juazeiro populations" were also found in wilderness and in peri-domiciliar environments. However, the natural infection rate for T. cruzi was negative for both. Even though, Petrolina and Juazeiro are located in different states (Pernambuco and Bahia, respectively). These two populations belong to neighboring sites which are separated by the São Francisco river, thus, sharing a parapatric condiction with the same environmental support capacity.
The "melanica population" was found only in wilderness, showing a different behavior from the other patterns examined. This pattern is clearly involved in the maintenance of the wild cycle of T. cruzi.
Regarding trophic resources, feeding eclecticism was observed for all different populations of T. brasiliensis. However, goat blood stood out in wilderness as well as in peridomiciliar areas for the four population samples analyzed. These data agreed with observations of Lent and Wygodzinsky (1979) and also with observations in field captures related to caprine herds, that roam from household surrounding areas to wilderness. This feature has shown the interconnection between these two ecotopes and perhaps the arbitrariness in discriminating their boundaries.
Several authors registered the occurrence of triatomine that presented positivity to more than one trophic resouce (Siqueira 1960, Pinto Dias et al. 1989, Salvatella et al. 1994). Romoser et al. (1989) emphasized the value to the knowdledge of the local fauna and the detection of any evidence of a host presence to obtain a better evaluation of the positive results for the different trophic resourses, mainly for phylogenetically related animals.
The fact that in Caicó, Petrolina and Juazeiro the different chromatic patterns have been found both in household and wild environments, indicates the possibility that in these sites the natural environment (rock cavy nests) could be suffering impact pressure and the feeding sources may not be fulfilling the basic needs, which would stimulate the invasion of new environments, as emphasized by Aragão (1975) concerning feeding opportunism. The wilderness is much poorer in vegetation in Caicó, Petrolina and Juazeiro than in Espinosa. Furthermore, in the three former sites, the high population density of T. sordida observed in Espinosa was not found. Thus the household surrounding areas at those sites offer less competitive conditions to allow colonization by T. brasiliensis.
According to information received from FNS, the low population density of triatomines found the peridomicile areas in Caicó results from the fact that it had recently been sprayed and is under permanent control, due to the high level of triatomine infestation found in the mentioned area. No other species were found during the searches. FNS records show that this species is frequent in household surroundings.
It was in the sites of Petrolina and Juazeiro that the species was found most remote from its natural environment. Indeed, it was collected in various human ecotopes, such as stables, chicken coops and other human artifacts. In Caicó, the specimens were collected in household surroundings, in environments that resemble natural ecotopes, i.e., stone walls, that somehow reproduced the rock cavy nests where they are found in wilderness. These walls are characteristic and frequently found in this region. They abundantly reproduce the features of the natural shelter of "brasiliensis population", because all housing units are bounded by this type of construction.
The "melanica population" seldom invades households in Espinosa (inhabitants and FNS, pers. com.). When the population density in the natural shelters at rock cavy nests increases rapidly at a certain time of the year, it becomes necessary to promote a burning of the nests, because the insects voraciously attack people who approach them, often to work with the rocks or in connection with agricultural activities.
Studies carried out by Gomes (1993) in two sites at São Raimundo Nonato, in Piauí, concerning the feeding profile and the mobility of T. brasiliensis and other triatomine species, have demonstrated that this species presents ample mobility and is found in household surroundings as well as indoors (bedrooms). Through the precipitin test, they demonstrated a high positivity for the armadillo blood (72.1%). Subsequently these specimens were examined concerning the chromatic patterns that define the T. brasiliensis populations. They were characterized as "brasiliensis population".
The broad ecological valence disclosed for different analyzed chromatic patterns of T. brasiliensis, through different colonized ecotopes, through variety of trophic resources and through natural infection rates stresses the need to increase environmental knowledge on the vectorial potential of T. brasiliensis in different areas not yet analyzed.
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