Wild Triatoma infestans, a potential threat that needs to be monitoredFranois NoireauUR 016, IRD, Montpellier, FranceIIBISMED, Facultad de Medicina, UMSS, Cochabamba, Bolivia

Triatoma infestans still remains the most important vector of Chagas disease in the Southern Cone countriesThe expected success of large-scale control campaigns relied on its almost exclusively domestic nature, precluding the recolonization of treated areas by insects from sylvatic environment

Current evidence that wild populations are much more widespread than previously thought

Known distributional range of wild Triatoma infestans in BoliviaHighland foci Inter-Andean Dry Forest 1,600 - 2,800 m aslLowland fociGran Chaco< 500 m asl

Existence of wild T. infestans in periurban environments Cochabamba (> 500,000 inhabitants):soaring urbanization near wild vectors refuges

Chromatic plasticity displayed by wild T. infestansCommon morphMataral morphDark morph

The different morphs of wild T. infestans

Name

Common morph

"Mataral" morph

Dark morph

Distinguishing morphochromatic traits

-

Large size

Markings on the connexivum

Overall dark coloration

Markings on the connexivum

Area of endemism

Inter-Andean Dry Forest (>2,000 m asl)

Inter-Andean Dry Forest, SE Cochabamba

(~1,700 m asl)

Gran Chaco

(

Natural ecotopes of Andean wild T. infestansFallen rocksRocky outcropsCliffs

Bioecological traits of a wild Andean T. infestans population30% of the rocky refuges contained T. infestans> 90% of nymphal instarsOne generation of triatomines per year Hosts and T. cruzi reservoirs: rodents and marsupials T. cruzi infection in vectors > 60% (TcI)Cochabamba valley, 2,700 m asl, rocky outcrops

Bioecological traits of the Chacoan dark morph T. infestansNatural ecotopes of T. infestans dark morph: hollow trees, cotorra nests (Myiopsitta monachus ) and bromelias10% of the emergent trees contained T. infestans> 90% of nymphal instarsHost: parrot (Amazona aestiva)* T. cruzi infection in vectors < 3%Tita, 350 m asl* Ceballos et al. 2009

The origin of T. infestans as a speciesFirst hypothesis: Chacoan origin of T. infestans: based on the occurrence, in the Chaco, of the other species with which T. infestans is closely relatedSecond hypothesis: Andean origin of T. infestans: allozymes, genome size and nuclear rDNA favor this hypothesis

The origin of T. infestans domestic populationsTraditional speculation Step 1: domestication of wild guinea pigs by Andean tribes about 5,000 BC Step 2: dispersal of domestic vectors in association with human migrations

The origin of T. infestans domestic populationsNew speculation Step 1: transport and distribution of maize hosting the associated fauna (wild rodents and insects) through the Inca EmpireStep 2: dispersal of domestic vectors in association with human migrationsDuring the Inca period, maize production and storage in the Cochabamba valley

Key question: threat represented by wild populations of T. infestansCan wild populations of T. infestans recolonize insecticide-treated villages and thus jeopardize control efforts?Several observations support the epidemiological risk represented by the wild T. infestans

1. Concerning the apparent distribution of T. infestans1. Maximum distribution reached during the 1970s (Gorla 2002)122. Current distribution (Schofield et al. 2006)Domestic T. infestans persist in areas where occur wild vectors

Various haplotypes (COI and Cytb genes) are shared by both domestic and sylvatic Andean populationsThe distinct "Mataral form, found in sylvatic environment in the southeastern Cochabamba department, is also colonizing houses of the same region2. Concerning the genetic and morphochromatic variability observed in T. infestans

3. Concerning the process of domestication of T. infestansT. infestans was, without any doubt, the triatomine species that displayed the most successfully completed process of domestication It is difficult to give credit to the hypothesis that wild forms of T. infestans would since then have become restricted to their natural habitat

Genetic diversity and dispersal ability in wild T. infestans at high altitude: collecting sitesRocky outcropsLarge block of rocksHousesNorthern hillWestern hillSouthern hillCochabamba valley, 2,700 m asl

Genetic diversity of wild T. infestans based on the mitochondrial CytB gene T. infestans collected in the sylvatic sites (3 hills and large outcrops) display genetic variation (7 hapl.)Western hillNorthern hillSouthern hillLarge outcropsHousesT. infestans from the houses display only one haplotype (C) also detected in wild triatominesTwo sylvatic haplotypes (A & C) were found in domestic bugs from the region of Sucre*Domestic triatomines from Cochabamba and Sucre display haplotypes also detected in sylvatic bugs* Giordano et al. 200546 T. infestans characterized

Dispersal ability

T. infestans does not disperse by flying at high altitude Microsatellite loci used to detect gene flow between neighboring collecting sites (< 1 km2)T. infestans disperses over continuous land cover (high significant Fst values)T. infestans does not disperse over land cover disrupted by man made activitiesNorthern hillWestern hillSouthernhillLarge PD rocks

Current hypothesesEvidences do not support a continued flow of T. infestans between sylvatic refuges and domestic environments In the Andes, the crepuscular coldness restricts flight dispersal and may hamper the process of domestic intrusion by wild T. infestansIn the Chaco, the emergent trees are become scarce in the vicinity of the villages. Consequently, the T. infestans "dark morph" would persist in preserved and remote wooded areasFinally, only unusual circumstances would generate a transfer of T. infestans from the natural to the domestic environment

ObrigadoIIBISMED Cochabamba: Team of Lineth GarciaPNCH: Mirko RojasFAN Santa Cruz: Teresa GutierrezIRD Montpellier: Team of Pierre KengneETS Cochabamba: Roberto RodriguezAgradecimientos:IOC FIOCRUZ Rio de Janeiro: Teams of Jos Jurberg and Ana Maria Jansen