Figure 8From: Factors influencing U.S. canine heartworm (Dirofilaria immitis) prevalence2007 U.S. county water coverage (Percent). County surface water coverage was obtained from the Census Bureau[12] and was calculated by dividing the surface water area by total county area reported in the Census Bureau[12]. The surface water coverage data were last updated in 2011, which were used in our analysis.Back to article page