The use of morphometrics in entomological surveillance of sylvatic foci of Triatoma infestans in Bolivia.

Jamach'uma (Cochabamba, Bolivia) is a small village surrounded by sylvatic foci of Triatoma infestans. Houses in the village were also infested with T infestans, and were sprayed in December 1992 as part of a Chagas disease vector control trial. Ten months later the houses were found to be again infested with a few fifth instar nymphs of T. infestans. These nymphs were compared by seven head measurements with 36 fifth instar nymphs collected from houses in Jamach'uma before treatment, and with two sets of nymphs originating from the surrounding sylvatic foci: eight specimens collected in 1992 and nine specimens collected in 1995. The results are discussed in relation to the possible mechanisms of the apparent reinfestation: recrudescence of a residual domestic population or reinvasion of the houses from surrounding sylvatic foci. Quantitative comparisons support the former hypothesis.