who are not paying attention. The American Heartworm Society has reported for years on the continued spread of. heartworm into new areas, has reported on some 250,000 dogs being found infected each year in the United States, and basically has mapped it to each of the lower 48 states (Guerrero et al. 2006). In an IDEXX-sponsored survey of clinics that included some 3 million data points for dogs, the map was basically the same as that generated by the AHS (Bowman et al. in press). Similarly, a clinic survey done by Novartis in the western United States showed a