POPULATION-STRUCTURE OF ANDEAN TRIATOMA-INFESTANS - ALLOZYME FREQUENCIES AND THEIR EPIDEMIOLOGIC RELEVANCE

Triatoma infestans (Hemiptera: Reduviidae) from 22 Andean localities i n Bolivia (n=968) and Peru (n=37) were analysed by multi-locus enzyme electrophoresis. Among 12 gene-enzyme systems analysed, GPD, 6GPD and PGM were polymorphic. ACON, G6PD, GPI, IDH, LAP, MDH, ME, PEP-A and PE P-B were monomorphic. Allozyme frequencies were analysed in relation t o geographical and climatic factors. and the presence or absence of Tr ypanosoma 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 di fference was found amen nymphs (n = 347). From other localities, only insects infected with 7 cruzi were subjected to isozyme analysis. Popu lations of 7: infestans within villages showed panmixia, while genetic differentiation of T. infestans between villages was correlated with the distance between them. The genetic structure of T. infestans natur al populations followed an 'isolation by distance' model, involving a series of founder effects followed by genetic drift, rather than adapt ation in response to differential selection pressures. This conforms w ith circumstantial evidence that 7 infestans spread, mainly in associa tion with recent human migrations, from a source, probably in southern Bolivia. Isoenzyme characterization of populations of T. infestans co uld be used to infer sources of re-infestation during the surveillance phase of control programs.