Ross M Boyce, MD, MSc, discusses the diagnostic challenges and the need for greater awareness of tick-borne illnesses in the US, considering their potential severity.
A new study out of North Carolina reveals that most patients tested for potentially serious tick-borne diseases like ehrlichiosis and spotted fever rickettsiosis are not completing the full two-step testing process necessary for a confirmed diagnosis, leaving significant gaps in public health surveillance and clinical care.
Researchers analyzed more than 4,400 patient records from a major academic center in North Carolina between 2017 and 2020. They found that while thousands received an initial (acute) blood test, only 15% returned for the follow-up (convalescent) sample needed to confirm the diagnosis.
This low rate of testing completion is a problem not only for individual patient care but for understanding how widespread these diseases are. “Unfortunately, very few people actually get the second test done,” said Ross M Boyce, MD, MSc, an infectious disease physician at the University of North Carolina, in our interview. “Nationally, it’s probably around five to eight percent of all people. So that informs a lot of the data and our knowledge of these diseases. And the lack of completion of that is really important.”
Tick-borne illnesses like ehrlichiosis and Rocky Mountain spotted fever are caused by bacteria transmitted through tick bites. They can cause symptoms such as fever, body aches, headache, and in some cases, rashes. “Certainly Rocky Mountain spotted fever and ehrlichiosis can be life-threatening if untreated,” Boyce said. “Particularly in children and older adults.”
Over the study period, completion of the convalescent testing did improve from 4% to 23% for Ehrlichia and 7% to 11% for Rickettsia though still far from ideal. Patients were more likely to complete the full testing algorithm if they lived near a health care facility, had a reactive result on the first test, or were tested for both pathogens.
Clinically, the two-part serological test is considered the gold standard, but it poses logistical hurdles. “It’s important first to note that you can’t use the test itself to make a diagnosis with just one visit,” Boyce explained. “The treatment decision has to be made just based on your clinical gut feeling.”
If a patient improves after treatment, many see no reason to return for another blood draw. “A lot of people feel better, and who wants to go back to the doctor just to confirm their result?” Boyce said. “It’s a harder case to say, well, this is important for us to know how many cases there are in an area. But it’s also important for people to confirm what it is they had.”
Even more critically, negative initial results can be misleading. “The first test can be negative just because your body hasn’t built up enough antibodies in response to the infection,” Boyce said. “Just because it’s negative during the first one does not mean that they are negative. In the same way, just because it’s positive… doesn’t mean they’re positive because they could have been exposed before.”
The current reliance on antibody-based testing comes with inherent delays and uncertainties. While some molecular diagnostic tools are available like PCR tests for Ehrlichia, they aren’t widely accessible or fast enough for real-time clinical decisions.
Fewer than 1 in 5 patients complete the full two-step testing process for ehrlichiosis and spotted fever rickettsiosis, leading to underdiagnosis and poor disease tracking.
A negative initial test can be misleading, and follow-up testing is essential to confirm or rule out infection.
Tick-borne illnesses like ehrlichiosis are spreading geographically but remain underrecognized and underfunded compared to Lyme disease.
“Rickettsia has always been a challenge,” Boyce said. “It invades the endothelium, the walls of the blood vessels, and there’s not as much floating around in the actual blood. When you stick a needle in and draw someone’s blood, unless you get a good chunk of the wall, you’re not going to get a lot.”
There are CDC-run PCR tests for Rickettsia, but those are limited and slow, requiring routing through public health agencies. “There’s a lot of people working on better tests,” Boyce added. “Rocky Mountain spotted fever is the most lethal tick-borne disease in the United States, but it has close cousins, that are not lethal at all. And the serological test can’t tell them apart, they all cross-react.”
Beyond diagnostics, Boyce said tick-borne illnesses like ehrlichiosis and spotted fever rickettsiosis suffer from a lack of public awareness and funding, often overshadowed by Lyme disease, "These diseases, I think, get a short shrift compared to Lyme, and there's definitely more cases of Lyme reported every year, but these are spreading, and it's spreading because the ticks that transmit them are moving into places.”
Boyce pointed to the Lone Star tick, known to transmit Ehrlichia, which has been reported in areas as far north as Maine and Canada. “They’re on the move,” he said. “Certainly worth thinking about and getting more attention.”
Tick-borne illnesses like Rocky Mountain spotted fever may be less well-known than Lyme, but they can be deadlier and are highly preventable with timely treatment. Boyce explained urgency, “Lyme doesn’t kill people in the short term. These can. Especially in kids. Especially in older adults. Especially if you don’t get treated within five to seven days.”
Until more rapid and reliable diagnostic tools become standard, clinicians must rely on clinical judgment, timely treatment, and improved follow-up to manage these potentially severe diseases. As Boyce noted, greater public and institutional awareness is key. With tick ranges expanding and case numbers rising, Boyce and his team hope their research will help drive attention to these often-overlooked yet increasingly relevant public health threats.
