Abstract
#Triatoma infestans$ (#Hemiptera$ : #Reduviidae$) from 22 Andean localities in Bolivia (n=968) and Peru (n=37) were analysed by multi-locus enzyme electrophoresis. Among 12 gene-enzyme systems analysed, GPD, 6GPD and PCM were polymorphic, ACON, G6PD, GPI, IDH, LAP, MDH, ME, PEP-A and PEP-B were monomorphic. Allozyme frequencies were analysed in relation to geographical and climatic factors, and the presence or absence of #Trypanosoma cruzi$ infection. At one locality (Vallegrande, Bolivia), the frequency of 6Pgd-1 was significantly higher in infected (41% of 85) than in uninfected (17% of 83) adult #T. infestans$, although no such difference was found among nymphs (n=347). From other localities, only insects infected with #T. cruzi$ were subjected to isosyme analysis. Populations of #T. infestans$ within villages showed panmixia, while genetic differenciation of #T. infestans$ between villages was correlated with the distance between them. The genetic structure of #T. infestans$ natural populations followed an "isolation by distance" model, involving a series of founder effects followed by genetic drift, rather than adaptation in response to differential selection pressures. This conforms with circumstantial evidence that #T. infestans$ spread, mainly in association with recent human migrations, from a source, probably in southern Bolivia. Isoenzyme characterization of populations of #T. infestans$ could be used to infer sources of re-infestation during the surveillance phase of control programs. (Résumé d'auteur)