Isozyme heterogeneity and numerical taxonomy of Trypanosoma cruzi stocks from Chile

Abstract

Fifty-three stocks of Trypanosoma cruzi were isolated in Chile, 13 from patients, 32 from the domestic triatomine vector Triatoma infestans, and 8 from the silvatic and peridomestic vector T. spinolai. The majority of isolates from triatomine bugs were made by the direct culture of infected faeces. The 53 stocks and a single clone were characterized by a combination of starch-gel and cellulose acetate enzyme electrophoresis. Three groups of T. cruzi stocks were apparent from either simple visual comparisons of isozyme profiles or numerical taxonomy. The groups were designated Chilean zymodeme (Z) 1, which was similar to Brazilian Z1, Chilean Z2a, similar to Brazilian Z2 and Chilean Z2b, similar to Bolivian Z2 and with prominent heterozygous isozyme profiles. Chilean Z1 was isolated only from T. spinolai colonizing farm walls inhabited by the rodent Octodon degus. Chilean Z2a and Z2b were both isolated from domestic T. infestans T. infestans and man, in some cases within the same household. Hardy-Weinberg equilibria were not found amongst a group of 22 stocks from a single locality and deviations from theoretical Hardy-Weinberg distributions were compatible with the absence of genetic exchange in the sampled population of T. cruzi.