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Summary Borrelia burgdorferi sensu lato (s.l.), transmitted by Ixodes spp. ticks, is the causative agent of Lyme disease. Although Ixodes spp. ticks are distributed in both Northern and Southern Hemispheres, evidence for the presence of B. burgdorferi s.l. in South America apart from Uruguay is lacking. We now report the presence of culturable spirochetes with flat-wave morphology and borrelial DNA in ende- mic Ixodes stilesi ticks collected in Chile from environmental vegetation and long-tailed rice rats (Oligoryzomys longicaudatus). Cultured spirochetes and borrelial DNA in ticks were characterized by multilocus sequence typing and by sequencing five other loci (16S and 23S ribosomal genes, 5S-23S intergenic spacer, flaB, ospC). Phylogenetic analysis placed this spirochete as a new genospecies within the Lyme borreliosis group. Its plasmid profi- le determined by polymerase chain reaction and pulsed-field gel electrophoresis differed from that of B. burgdorferi B31A3. We propose naming this new South American member of the Lyme borreliosis group B. chilensis VA1 in honor of its country of origin.

We compared spatial and temporal patterns of resource use by feral and abandoned domestic dogs (Canis familiaris) on the Navajo reservation in Arizona and New Mexico. Community dumps provide locally abundant food resources utilized both by feral dogs and dogs abandoned at the dump site. Although population parameters were much the same for feral and abandoned dogs, the use of space varied distinctly and reflected behavioral differences in the way each population responded to the absence of human control, the need to acquire food, and the developmental state of pups. Temporal use of resources by feral dogs varied seasonally with the age of pups in one pack, but not in a second pack. Priority of access to local resources may be influenced by aggressive interactions among dogs at a dump. Barking may serve to warn dogs already present at a dump that competitors have arrived.