Figure 1
From: Key factors influencing canine heartworm, Dirofilaria immitis, in the United States
Spatially smoothed proportions of positive canine heartworm-antigen tests recorded by US veterinarians in 2011. The figure summarizes 4,769,403 tests performed by veterinarians for circulating heartworm antigen in the US in 2011; of these tests, 56,612 tests (1.187%) were positive. The population studied is those dogs that are seen by a veterinarian and are tested; about 5% of owned dogs in the US. The map displays probabilities of a positive test after smoothing by the head-banging algorithm (see text for details). The figure is made by assigning the smoothed proportions to nine color-coded categories [0.00,0.03], (0.03,0.06], . . .,(0.21,0.24], and (0.24, 1.00]. The colors range from dark green for the lower proportions to bright red for higher proportions.