Wild Triatoma infestans , a potential threat that needs to be monitored

1. Wild Triatoma infestans, a potential threat that needs to be monitored François Noireau UR 016, IRD, Montpellier, France IIBISMED, Facultad de Medicina, UMSS, Cochabamba, Bolivia

2. Triatoma infestans still remains the most important vector of Chagas disease in the Southern Cone countries The 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

3. Known distributional range of wild Triatoma infestans in Bolivia Highland foci Inter-Andean Dry Forest1,600 - 2,800 m asl Lowland foci Gran Chaco < 500 m asl

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

5. Chromatic plasticity displayed by wild T. infestans Dark morph Common morph “Mataral” morph

6. The different morphs of wild T. infestans

7. Natural ecotopesof Andean wild T. infestans Rocky outcrops Cliffs Fallen rocks

8. Bioecological traits of a wild Andean T. infestans population Cochabamba valley, 2,700 m asl, rocky outcrops • 30% of the rocky refuges contained T. infestans • > 90% of nymphal instars • One generation of triatomines per year • Hosts and T. cruzi reservoirs: rodents and marsupials • T. cruzi infection in vectors > 60% (TcI)

9. Bioecological traits of the Chacoan “dark morph” T. infestans Tita, 350 m asl • Natural ecotopes of T. infestans “dark morph”: hollow trees, cotorra nests (Myiopsitta monachus ) and bromelias • 10% of the emergent trees contained T. infestans • > 90% of nymphal instars • Host: parrot (Amazona aestiva)* • T. cruzi infection in vectors < 3% * Ceballos et al. 2009

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

11. The origin of T. infestans domestic populations Traditional 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

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

13. Key question: threat represented by wild populations of T. infestans Can 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

14. Records of wild T. infestans 1. Concerning the apparent distribution of T. infestans 1 2 1. Maximum distribution reached during the 1970’s (Gorla 2002) 2. Current distribution (Schofield et al. 2006) Domestic T. infestans persist in areas where occur wild vectors

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

16. 3. Concerning the process of domestication of T. infestans T. 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

17. Genetic diversity and dispersal ability in wild T. infestans at high altitude: collecting sites Cochabamba valley, 2,700 m asl Northern hill Rocky outcrops Western hill Large block of rocks Houses Southern hill

18. Genetic diversity of wild T. infestans based on the mitochondrial CytB gene • 46 T. infestans characterized • T. infestans collected in the sylvatic sites (3  hills and large outcrops) display genetic variation (7 hapl.) Northern hill Western hill Large outcrops • T. infestans from the houses display only one haplotype (C) also detected in wild triatomines Houses • Two sylvatic haplotypes (A & C) were found in domestic bugs from the region of Sucre* Southern hill * Giordano et al. 2005 Domestic triatomines from Cochabamba and Sucre display haplotypes also detected in sylvatic bugs

19. Dispersal ability Microsatellite loci used to detect gene flow between neighboring collecting sites (< 1 km2) T. infestans disperses over continuous land cover (high significant Fst values) Northern hill Western hill Large PD rocks T. infestans does not disperse over land cover disrupted by man made activities T. infestans does not disperse by flying at high altitude Southern hill

20. Current hypotheses Evidences 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. infestans In 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 areas Finally, only unusual circumstances would generate a transfer of T. infestans from the natural to the domestic environment

21. Agradecimientos: PNCH: Mirko Rojas FAN Santa Cruz: Teresa Gutierrez IIBISMED Cochabamba: Team of Lineth Garcia ETS Cochabamba: Roberto Rodriguez IOC FIOCRUZ Rio de Janeiro: Teams of José Jurberg and Ana Maria Jansen IRD Montpellier: Team of Pierre Kengne Obrigado