Every dog owner is familiar with the routine: a quarterly beef-flavored chew to ward off ticks and a vaccine to prevent Lyme disease. It’s a simple, effective strategy that keeps our pets safe. But when it comes to similar protections for humans, the options are notably absent. This discrepancy raises a question: why are there robust preventive measures against ticks for dogs but not for people?
Dr. Linden Hu, a professor of immunology at Tufts University School of Medicine, notes, “It’s funny, in Lyme disease, animals have so many more options than humans do.” This includes several vaccines and both oral and topical tick-prevention medications. The lack of human equivalents, however, stems from several factors, including safety concerns and doubts about public acceptance.
The Brief Life of a Human Lyme Vaccine
Historically, there was a Lyme disease vaccine for humans. Between 1999 and 2002, a drug called Lymerix was available in the United States. Approved by the FDA in 1998 after clinical trials confirmed its safety and efficacy, it was recommended for people aged 15 to 70 in Lyme-prevalent areas. However, post-launch, reports of side effects, particularly symptoms mimicking arthritis, began to surface. Although federal health officials did not find concrete evidence linking the vaccine to these side effects, the damage to its reputation was irreversible. Sales plummeted, and by 2002, the manufacturer, GlaxoSmithKline, withdrew it from the market.
The incident left a lasting impact on the perception of Lyme vaccines for humans, making pharmaceutical companies hesitant to invest in new developments despite the growing rates of Lyme and other tick-borne illnesses.
New Vaccines on the Horizon
In response to the increasing need, major pharmaceutical players like Pfizer, Valneva, and Moderna have developed new human vaccines targeting the same OspA protein used in the dog vaccines. These proteins are produced by the Lyme-causing bacteria and transmitted through tick saliva. When a tick ingests blood containing these antibodies, the bacteria in the tick’s gut are neutralized, preventing infection.
These new vaccines have been reformulated to hopefully avoid the pitfalls of their predecessor. Currently, they are undergoing clinical trials with results expected in the coming years. This marks a significant step forward in potentially providing humans with effective Lyme disease prevention.
Topical and Oral Preventatives: A Veterinary Success
For pets, another line of defense against ticks comes in the form of oral and topical treatments known as acaricides. These substances, safe for dogs at prescribed doses, effectively kill ticks and other parasites like fleas and mites upon contact. Their success in veterinary medicine is well-documented, providing protection against multiple tick-borne diseases.
Dr. Janet Foley, a professor of medicine and epidemiology at the University of California, Davis School of Veterinary Medicine, explains that these treatments are effective because they kill ticks quickly, often within hours of attachment, thus preventing disease transmission.
The Challenge of Adapting Veterinary Medications for Human Use
The adaptation of veterinary medications for human use is not straightforward. Dr. Hu mentioned that the idea of using acaricides as prophylactics for humans has only recently been considered. The concern is understandable; the notion of ingesting or applying a toxin as a preventative measure may not sit well with the public. Moreover, the market for such a product among humans is speculative at best.
However, Tarsus Pharmaceuticals is exploring this possibility. In collaboration with Dr. Hu, they are testing an oral acaricide called lotilaner—already used in veterinary medicine and recently approved as an eye drop for humans—in pill form to see if it’s safe and effective against ticks on humans.
Looking Ahead: The Future of Human Tick Prevention
The road to FDA approval for these new human medications is long, filled with additional rounds of clinical trials. The outcome and public reception remain uncertain. Dr. Hu, who has experience with the Moderna vaccine, comments on the unpredictable nature of public acceptance, highlighting that even with approval, the community’s reception can vary widely.
As research continues and new products are tested, the hope is that effective tick prevention methods for humans will soon be available, mirroring the protections we currently afford our pets. The journey from veterinary to human medicine is complex and fraught with challenges, but the potential benefits are significant, promising a future where Lyme disease and other tick-borne illnesses are no longer a looming threat for outdoor enthusiasts and those living in high-risk areas.
