Infections of inbred mice with three Trypanosoma cruzi isolates from Louisiana mammals.

r: Trypanosoma cruzi isolates from a dog (TcD), opossum (Tc-O), and an armadillo (Tc-A) from southern Louisiana were inoculated into 6 inbred mouse strains. None of the isolates produced fatal infections in the mouse strains tested. Parasitemias were quantified over 34 days and found to be similar in mouse strains infected with Tc-O and Tc-A. Parasitemias in Tc-D-infected mice were detectable only by blood culture. Pseudocyst numbers, inflammatory changes, and weight changes were quantified in CF1 mice infected with the 3 isolates. Tc-Oand Tc-A-infected CF1 mice were shown to be myotropic and produced comparable weight increases, pseudocyst numbers, and inflammatory changes in similar tissues. Tissues found to contain pseudocysts were muscles of the bladder, abdominal wall, thigh, heart, and diaphragm. Clinical signs of infection, pseudocyst numbers, and inflammatory changes were minimal in Tc-D-infected CF1 mice. Tissue tropism of this isolate was not determined. The in vivo infectivity characteristics of these isolates suggests that Tc-O and Tc-A are similar and differ markedly from Tc-D. Assessments of infectivity, virulence, and tissue tropism in inbred laboratory mice are common methods used to characterize and compare Trypanosoma cruzi isolates (Watkins, 1966; Zeledon and Ponce, 1972), and clones from a common source (Postan et al., 1986). In this study, we compare the course of infection of T. cruzi isolates from a naturally infected dog, opossum, and armadillo from southern Louisiana in 6 inbred mouse strains. We also detail the clinical disease, pathology, and tissue tropism of the T. cruzi isolates in CF1 mice. The 3 T. cruzi isolates were recovered from a dog (Tc-D), an armadillo (Tc-A), and an opossum (Tc-O) from southern Louisiana and maintained in African green monkey kidney (Vero) cell culture as described previously (Barr et al., 1986; Barr, 1989). Trypomastigotes harvested from Vero cell cultures were used for all infections at a concentration of 1 x 107 organisms/ ml in MEM (GIBCO, Grand Island, New York) supplemented with 10% heat-inactivated (56 C, 30 min) fetal calf serum (FCS), 100 IU of penicillin and 100 ,g of streptomycin/ml of medium (antibiotics). Fiveto six-week-old male mice from 6 inbred strains (C3H, CF1, C57B1, Balb/c; Harlan Sprague-Dawley, Inc., Indianapolis, Indiana; and CFW and CD 1 from Charles River Laboratories Inc., Willmington, Massachusetts) were infected with different T. cruzi isolates and were housed separately. Mice were kept in groups of 3-6 under controlled lighting conditions (12-hr cycles), received water and food ad libitum, and were kept on wood chip bedding. Mice were infected intraperitoneally (i.p.) with 1 x 106 trypomastigotes in 0.1 ml MEM from 1 of the 3 T. cruzi isolates. Controls received 0.1 ml of MEM i.p.