Home Economics American Trypanosomiasis Chagas Disease, Second Edition: One Hundred Years of Research
There are 13 recognized species within the genus Panstrongylus that have a wide geographic distribution throughout the Neotropical region, extending from Mexico to Argentina.44 Among these species, some appear to be involved in a process of domiciliation, showing the ability of the species to colonize human dwellings (P. genicula- tus, P. rufotuberculatus, P. lutzi, and P. chinai). Other species are more opportunistic and occasionally fly from the sylvatic environment to houses without colonizing (e.g., P. lignarius in the Amazon basin). The phylogeny of the group is currently under discussion, although there is evidence suggesting the existence of a northern and a southern clade that are parallel to the northern and southern clade of Triatoma species; Panstrongylus species are considered to be evolved from this latter clade.45
Although some species can be found in palm tree crowns (e.g., P. megistus), all species are associated with terrestrial burrows, tree-root cavities, or hollow trees.25 P. geniculatus and P. rufotuberculatus have the widest geographic distribution, extending from Mexico to Argentina, including the Caribbean Islands (found in 18 and 10 countries, respectively). P. lignarius is the third most widely dispersed and it is found in seven South American countries. P. megistus is restricted to eastern and central South America. The remainder of the species have more limited or undetermined geographic distributions. P. geniculatus has been considered a eury- thermic species, meaning that it is adapted to several dry as well as humid ecotopes, and it is found in a great variety of sylvatic habitats (very dry forests or savannahs, dry, wet, moist, and rainy forests). This species is frequently captured in peridomes- tic environments and its occurrence inside houses has been cited in several countries.25,46-48 This species has epidemiological importance because of the high incidence of blood-fed specimens on humans concomitantly infected with T. cruzi I in Venezuela.48 The ingestion of fruit juice accidentally contaminated by P. genicu- latus is thought to have caused an outbreak of infections in 2007 in Caracas possibly via oral transmission.
P. rufotuberculatus is generally considered to be a sylvatic species ranging from Mexico to Argentina. This species has been found in palms, hollow trees, and the refuges of wild mammals.1,49,50 Adult insects frequently invade human dwellings as they are attracted by electric light.1,51,52 Breeding colonies have been found inside dwellings in Bolivia, Ecuador, and Peru.39,53,54 P. rufotuberculatus has been incriminated as a vector of Chagas disease in Andean and coastal foci of Ecuador. In the municipality of Amalfi (Antioquia, Colombia), the presence of P. rufotuberculatus is an epidemiological risk factor.55 Several characteristics that could be linked to high vectorial capacity were observed for this species, including longevity, rapid response to the presence of a host, large volumes of blood ingested, and frequent defecation during the feeding process.56
P. megistus has a wide geographic distribution, ecological valence, and great potential for the colonization of artificial ecotopes. This species occurs in all varieties of Brazilian forests, including dry and moist humid forests in the Cerrado and Caatinga. The species is usually associated with humid forests from where adults can invade houses,57 especially during the rainy season.58 In other countries, such as Argentina, Bolivia, Paraguay, and Uruguay, P. megistus is almost entirely sylvatic.59 On the occasions when this species is found in domestic habitats, it is usually associated with synanthropic hosts, especially opossums.60 P. megistus was considered the main domestic vector in Brazil until it was progressively replaced by T. infestans, probably since 1930.58,61 Following the success of the Southern Cone Chagas Disease Control Programme (INCOSUR) that achieved the elimination of T. infestans in many areas,62 P. megistus reinitiated house invasion and is once again domiciliated in several states of Brazil. Thus, P. megistus is currently considered to be the main autochthonous vector of Chagas disease in the central, eastern, and southeastern regions of Brazil. The most strongly synanthropic species, P. lignarius (formerly P. herreri), is considered to be the principal vector of Chagas disease in Peru.54
Transmission of sylvatic T. cruzi to humans has also been associated with P. lig- narius. In the Amazon basin, this species was observed flying from palm trees (A. phalerata) to houses.63 In Colombia, this species has been found in bird nests and it is not considered of epidemiological importance.64
P. lutzi is one of the most important secondary vectors in Brazil. It has great capacity for invading houses through flight and shows high rates of natural infection with T. cruzi, likely due to the close vector association with armadillos.26 P. chinai may act as the vector of T. cruzi in sylvatic cycles in arid areas of northern and eastern Peru (Vazquez-Prokopec et al., 2005) as well as southeastern Ecuador.65 P. howardi is considered to be a potential vector of T. cruzi in the coastal region of Ecuador.65 The remaining Panstrongylus species (P. diasi, P. guentheri, P. humeralis, P. lenti, P. mitarakaensis, and P. tupynambai) have not been described as vectors of T. cruzi to humans, but most of them are probably involved in sylvatic T. cruzi cycles.45
|< Prev||CONTENTS||Next >|