Association between nutritional indicators and infectivity of dogs seroreactive for Trypanosoma cruzi in a rural area of northwestern Argentina

The association between the nutritional state of mongrel dogs naturally inf ected with Trypanosoma cruzi and their infectivity to Triatoma infestans bu gs and immune response to Trypanosoma cruzi were studied in the rural villa ge of Amama, northwestern Argentina. All of the 97 evaluated dogs were clas sified into one of three categories of external clinical aspect (ECA) based on the degree of muscle development, external evidence of bone structures, state of the hair of the coat, existence of fatty deposits, and facial exp ression. ECA was significantly associated with two nutritional indicators, hematocrit and skin-fold thickness, but not with total serum proteins. For all dogs, hematocrit was significantly correlated with skin-fold thickness. The 2-year survival probability decreased significantly from 60.7% for dog s with good ECA to 45.9% and 31.2% for those with regular and bad EGA, resp ectively. The age-adjusted relative odds of infection for Triatoma infestan s xenodiagnosis nymphs that fed once on a dog seroreactive for Trypanosoma cruzi decreased significantly as ECA improved, when tested by multiple logi stic regression analysis. A delayed hypersensitivity reaction was observed in all of the seroreactive dogs with good ECA but only in 45-50% of those w ith regular or bad EGA. Dogs with bad ECA had a 2.6 and 6.3 times greater p robability of infecting triatomines after a single full blood meal than dog s with regular or good EGA, respectively. Our study shows that the reservoi r competence of does for Trypanosoma cruzi was associated with EGA, which i s a surrogate and valid index of nutritional state.