American Heartworm Society releases new incidence data
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The American Heartworm Society released results in May of its latest survey of heartworm incidence in the United States.
The AHS Heartworm Incidence Survey has been conducted every three years since 2001 for the purpose of tracking trends in heartworm incidence and informing the public about the need for year-round heartworm prevention. The latest survey focused on heartworm diagnoses in 2010, representing data from more than 5,000 veterinary clinics across the country on clinic testing and heartworm-positive dogs and cats.
Weather believed to have influenced heartworm transmission rates
The likely influence of weather patterns on mosquito populations is discernible when comparing the 2010 AHS Heartworm Incidence map with a similar map from 2007. “The pattern of heartworm incidence overall was similar to that of previous years,” said AHS president Wallace Graham, DVM. “We believe that because the summer of 2009 was cooler in some areas of the country and drier in others, mosquitoes—and heartworm—
were somewhat more concentrated in areas with nearby standing bodies of water.” Study supervisors noted that survey clinics reporting low numbers of heartworm-positive animals often sat side-by-side with clinics with high numbers.
By contrast, Graham explained, the previous 2007 study reflected the homogenizing effects severe weather can have on mosquito populations. In 2007, the fallout from Hurricanes Katrina and Rita had far-reaching effects on mosquito vectors and heartworm transmission.
Veterinary vigilance encouraged
“The key point to remember is that none of us can predict the weather and know in advance whether or not the conditions will be ripe for heartworm transmission,” said Graham. He added that additional factors play roles in transmission, including wildlife that serve as reservoirs for infection and a likely decrease in the number of protected dogs, due to documented decreases in purchases of heartworm preventives.1 “AHS recommends that veterinarians be vigilant about recommending annual heartworm testing and year-round use of heartworm protection. Without such vigilance, heartworm incidence numbers could climb higher than ever before.”
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