CONICET | Buscador de Institutos y Recursos Humanos

We analyzed the variability of susceptibility to deltamethrin in putatively susceptible Triatoma infestans Klug (Hemiptera: Reduviidae), and evaluated the sample size implications on the hypotheses used in the current World Health Organization protocol for the measure of insecticide resistance in Triatominae. Following the protocol, using topical application of deltamethrin to unfed Þrst instar nymphs of T. infestans,we found that susceptibility showed signiÞcant differences between offspring from different females, a signiÞcant association with female age, and signiÞcant interaction female female age. Considering individual female data, three patterns of nymphal mortality were identiÞed: one showed a strong positive relation between nymphal mortality and their motherÕs age, another showed high mortality with low variability and the third showed intermediate mortality with high variability along female age. The analysis suggests revision of the World Health Organization protocol for resistance detection in Triatominae, not only to take into consideration the sources of variation in susceptibility, but also the effects of sample size in relation to the signiÞcance and power probabilities of the test.