Lyme disease is spreading across the US but your dog can help track it
As the climate warms, Lyme disease is spreading. To assess the risk of catching the infection in new areas, we need to be able to track the ticks that carry it. Now an analysis of veterinary records suggests dogs are the answer.
Lyme disease can lead to heart failure or paralysis but we don’t monitor how many people come into contact with the bacterium that causes it. “We don’t screen ourselves for exposure,” says Jenna Gettings at the University of Georgia. “The only time people are tested for tick-borne disease is when they have symptoms. Whereas with dogs, we screen healthy animals.”
In the US, pet dogs are tested for Lyme disease at yearly health checks, and their data is reported to a central database. It’s currently possible to share veterinary records widely, as these don’t have the same kinds of privacy concerns as human health data, says Gettings.
She and her colleagues analysed data from more than 16.5 million dog screening test results from 2012 to 2016. The test detects if dogs have produced antibodies to Borrelia burgdorferi, the Lyme-causing bacterium that can be passed to animals and people in tick bites. Because dogs tend to go to the same places as their owners, their data should reveal where people are at the most risk of contracting the disease.
When the team compared the dog data with the reported rates of Lyme disease in humans during the same five-year period, they found an association between the two. In counties where 0 to 10 per cent of dogs screened positive for B. burgdorfei exposure, there was a rapid increase in human incidences of Lyme disease.
In areas where 10 to 30 per cent of dogs screened positive, human rates also rose, but more slowly. In areas where more than a third of dogs encountered the bacterium, there was no link between dog and human data.
“We don’t fully understand why the association drops off,” says Gettings. “It may be that we don’t have a ton of data at that level.” Thankfully, not many counties in the US have such high levels of dog exposure to the bacterium, she says.
Because vets mostly test dogs at annual check-ups, this data can’t tell us how Lyme is changing over short periods of time. It also can’t take into account when a pet dog contracted Lyme disease outside of their home county. Nevertheless, the team found that the data could be used to build a model that helps predict where Lyme disease may be spreading.
“Where the value of this analysis seems to be the greatest is in the sort of leading edge of the range of Lyme disease,” says Rick Ostfeld at Tufts University in Massachusetts. “In places where incidence is low, it may be that the dog data is a good sentinel for us.”
In places where Lyme is endemic in the US – the Northeast and the upper Midwest – public health officials and doctors make people aware of their risks and give advice on how to avoid tick bites. But people living in counties where Lyme hasn’t historically been a problem may be caught unawares as ticks and the diseases they carry spread into their area. This new model could help give people a much-needed warning, Ostfeld says.
Journal reference: Geospatial Health, DOI: 10.4081/gh.2019.750
Again, climate change has nothing to do with this: https://madisonarealymesupportgroup.com/2018/11/07/ticks-on-the-move-due-to-migrating-birds-and-photoperiod-not-climate-change/