2017 could be a record year for ticks and tick-borne illnesses according to one researcher who studies the arachnids in Alabama.
"I would say this is going to be a very bad tick year because it was a very mild winter," said Tim Sellati, chair of Southern Research's Infectious Diseases Department.
The warm, wet winter and spring have created conditions for dense undergrowth in forests, which allows ticks to thrive.
In addition, Sellati said a warming climate has let certain species of ticks expand their range and those changes are reflected in tick surveys in Alabama and other parts of the United States. Ticks of Alabama, how to remove them
"The winters are warmer and the ticks recognize this, they sense this change in their environment," Sellati said. "We are seeing, year over year, ticks migrating into areas they would not normally venture into.
"The ticks take advantage of this change in climate that allows them to expand their range. When ticks expand their range, they also increase the likelihood of coming in contact with humans."
You can get Lyme disease in Alabama
There's a persistent myth that Alabama doesn't have Lyme disease or the ticks that carry it, but Sellati and others say that is absolutely false.
Alabama has both the black-legged tick (often called the deer tick) and the bacteria that causes Lyme disease, Borrelia burgdorferi.
Sellati said that biological surveys conducted by Auburn University show the most common tick in Alabama is the lone-star tick, with adults carrying a distinctive white spot on their back, but Alabama also has black-legged ticks, American dog ticks and Gulf Coast ticks in the southern part of the state.
The most commonly found ticks in the Southeast are (clockwise from top left) the black-legged tick (commonly called deer tick), the American dog tick, the lone-star tick, and the Gulf Coast tick.
Sellati said it may just be a matter of knowing where and how to look for the ticks. The more aggressive lone-star ticks may respond better to the most common method of tick sampling, which is to place dry ice (carbon dioxide) on a white sheet in the woods and wait. The ticks are attracted to the CO2 from the dry ice and can easily be collected from the white sheet.
When researchers collected samples from deer, they predictably found more deer ticks than lone-star ticks.
The genetics of Lyme disease
While entomologists track ticks in the wild, and the Alabama Department of Public Health collects data on tick-borne illnesses, Sellati and his team at Southern Research are interested in how genetics impacts a person's reaction to the bacteria that causes Lyme disease.
Sellati said 20 to 30 percent of people who are infected with the Lyme bacteria, show no symptoms or complications whatsoever.
"It's as if they weren't even infected, but they were," Sellati said. "Their immune system has the ability to recognize that bacteria, kill it and clear it very effectively."
Fifty to sixty percent show the trademark bullseye rash, as well as arthritis, carditis, nervous system effects, or other symptoms, but are treated with antibiotics and show no permanent ill effects.
The remaining 20 to 30 percent, even if they receive the same antibiotic treatment as the majority group, experience symptoms that persist even after their treatment.
"The combination of their immune response and the antibiotics is not enough to eliminate the symptoms of Lyme disease," he said. "These individuals have a significant decrease in their quality of life after infection."
Sellati said there is still debate among the scientific community as to whether this happens because the antibiotics don't completely kill the bacteria, or whether permanent damage was done before the antibiotics were administered.
Regardless, Sellati said he is working to understand whether genetic differences could be responsible for the varied reactions to the bacteria.
Electron micrographic (SEM) image of an unidentified engorged female tick which had been extracted from the skin of a pet cat.
Sellati said he has identified one strain of mouse that develops a "very severe Lyme arthritis," and another strain that exhibits "very mild if any symptoms" when exposed to the Lyme-causing bacteria.
"This gives us a beautiful model to study the genetics of these mice and what makes them so different in how they respond to the bacteria," Sellati said. "We're starting to understand these key genetic differences that influence the severity and the persistence of the symptoms.
"So we can test drugs in mice that will complement their immune response, which is lacking, and hopefully these new drugs will help those individuals that are predisposed to developing those Lyme disease symptoms."
Sellati said the researchers could be close to identifying genetic markers that would lead to better treatments for the 300,000 people diagnosed with Lyme disease diagnosed each year in the United States.
"When you go to your physician with a tick bite, we could test you rapidly to see whether antibiotics alone are likely to kill and clear all the bacteria," Sellati said. "Or does your genetic profile suggest that antibiotics are not going to be enough."