Are cats and dogs the major source of endotoxin in homes?

Previous studies have suggested that exposure to cats and dogs during early childhood reduces the risk of allergic disease, possibly by increasing home endotoxin exposure. This study asked the question of whether cats and dogs are the dominant influence on dust endotoxin concentrations in homes after considering other variables reportedly associated with endotoxin. The presence of cats or dogs in homes, household and home characteristics, and dust endotoxin concentrations from 5 locations were assessed in 966 urban and suburban homes. Whether considered together as pets or as cats and dogs separately, the presence of cats and dogs significantly contributed to living room and bedroom floor endotoxin concentrations, but not to bed endotoxin concentrations. However, the two variables consistently related to endotoxin in all home sites were the home occupant density (occupants/room) and cleanliness of the home. Our data suggest that reducing occupant density and improving home cleanliness would reduce home endotoxin concentrations more than removing pet cats or dogs from the home.     

Identification of pets and raccoons as sources of bacterial contamination of urban storm sewers using a sequence-based bacterial source tracking method

In urbanized areas, contaminated storm sewers can feed high bacterial levels into free-flowing streams and rivers. Although illicit connections sometimes cause contamination, urban wildlife and free-roaming domesticated or feral pets may be another source. After eliminating illicit connections as sources of high levels of Escherichia coli in two storm sewers tributary to the Huron River in southeast Michigan, the roles of urban wildlife, pets, humans, and birds were investigated using a sequence-based bacterial source tracking technology. After enumeration, E. coli were isolated from water samples collected during spring to fall, 2005. Sequences in the gene beta-glucuronidase of each isolate were compared to sequences of reference strains from humans, raccoons, pets (cats and dogs), and birds. The highest percentage source for six of ten events was pets (ANOVA, p=0.005). Among isolates attributed to pets, strains from cats occurred more frequently on seven of nine events in which pets had a non-zero probability. High raccoon percentages (up to 60%) occurred in late summer and fall, and varied significantly more than in the spring (F-test), possibly reflecting urban raccoon den-site mobility. The sequence-based bacterial source tracking method suggests that feces from pets and raccoons are important contributors to urban storm sewers.