A study published in mBio, “Polymicrobial Nature of Tick-Borne Diseases,” found that three species of ticks carry several agents that have the potential to cause human diseases.
Jorge Benach, professor of microbiology and immunology at Stony Brook University, and Rafal Tokarz, assistant professor of epidemiology at Columbia University, along with other co-authors tested 1,633 individual ticks collected from Suffolk County for 12 microbes.
The geographical spread of ticks poses a public health risk as cases of tick-borne diseases in the U.S. went up by more than 1,000 in a year from 48,610 in 2016 to a record number of 59,349 in 2017. The study reported that these emerging species of ticks bring new pathogens that are co-transmitted by deer ticks, leading to challenging diagnoses of polymicrobial infections.
“The whole idea was that tick-borne diseases are a sort of a complex of many different agents coming together,” Tokarz said. “Therefore, it is important for clinicians to be aware of it and to look at tick-borne diseases not just as Lyme disease, but to be aware of other agents that people may be infected with as well.”
The study found that more than half of the deer ticks were infected with the Lyme disease microbe and that, most significantly, a total of 22% were infected with more than one pathogen.
Santiago Sanchez-Vicente, postdoctoral associate at Stony Brook University, collected the ticks by dragging a one-square-meter strip of cloth in the woods of northern and southern sites in Long Island during the spring and fall of 2018.
According to Sanchez-Vicente, the expansion of ticks in the region is a result of insular and anthropogenic reasons, as well as climate change.
“Islands are very sensitive ecosystems,” he said. “When invasive species invade the island, it serves as a container for these species. It’s easy to get in, but it’s hard to get out. That is why the lone star americanum is taking over the territory.”
The amblyomma americanum, or lone star tick — a southern tick species that has entered Long Island — is capable of transmitting a pathogen that causes ehrlichiosis, a disease with flu-like symptoms.
As reported in the study, the number of reported cases of ehrlichiosis in Suffolk County has increased and the growing population of lone star ticks will further spread this emerging infection.
Sanchez-Vicente and Benach were astounded to find the large number of pathogens in the ticks. Their work emphasized the need for a polymicrobial approach because the same species of ticks can transmit more than one infection, affecting patients’ diagnoses and treatments.
“I think that the world of public health needs to realize that there’s more than one organism circulating in Long Island ticks,” Benach said. “I think ordering the right tests and having the approach of the possibility that there could be more than one organism is something that they need to consider.”
The clinical approach in tackling polymicrobial infections in humans is critical when their illnesses become more severe because of undergoing synergistic effects. When patients are suffering from an infection with multiple pathogens, their immune systems are altered in different ways, especially when antibiotic treatments have no effect in eradicating the infection altogether.
One of the goals of the study is to open discussions and studies that explore how these pathogens influence each other and the way they impact the courses of future infections.
“We definitely need to keep doing tick-surveillance studies. Suffolk County is doing tick-surveillance studies, but they’re only focused on the known pathogens. Our study discovers potential new pathogens and this is important,” Sanchez-Vicente said.