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When I tell people I study parasites that live inside ticks, I usually get one of two reactions: a shudder of disgust or a puzzled look that says, "Don't ticks already carry enough diseases?"

They're not wrong to be concerned. But what keeps me up at night is this: we're only seeing part of the picture. After spending months analyzing decades of research for my recent review, I discovered that North America has documented only three types of tick-borne parasitic worms, while other continents have found many more. Are these parasites truly absent here, or have we simply not been looking?

Three years ago, when I started my graduate work at Texas A&M University, I was fascinated by the complex relationships between parasites and their hosts. As I dove deeper into the scientific literature on filarial nematodes—microscopic worms that use ticks as vehicles to move between animals—I noticed something troubling.

While researchers worldwide were documenting diverse tick-borne filarial nematodes, North America seemed strangely quiet.

I spent months combing through research papers, creating spreadsheets, and mapping distributions. The picture that emerged was both fascinating and alarming. My colleagues Dr. Jessica E. Light and Dr. Guilherme G. Verocai and I compiled our findings into a comprehensive review that revealed significant gaps in what we know about these parasites in North America.

Imagine investigating a crime scene but only looking for certain types of evidence. That's essentially what we've been doing with tick surveillance in North America. We search for the usual suspects—Lyme disease, Rocky Mountain spotted fever—but we're missing an entire category of potential threats.

Our review documented five genera of filarial nematodes worldwide that use ticks as vectors: Cercopithifilaria, Cherylia, Cruorifilaria, Monanema, and Yatesia. Another genus, Acanthocheilonema, has been detected in ticks through DNA analysis, though we haven't confirmed that ticks can actually transmit it.

Here in the United States, we know the brown dog tick carries Cercopithifilaria bainae, a parasite that can cause skin problems in dogs. But that's just one species in one tick. What else might be out there?

Let me paint a picture of what happens when these parasites go undetected. A dog comes into a veterinary clinic with unusual skin lesions. The vet runs standard tests for tick-borne diseases—all negative. They prescribe antibiotics, maybe steroids. The dog doesn't improve. Why? Because the real culprit is a filarial nematode that nobody thought to look for.

The situation gets more complicated. During our review, we discovered these parasites don't travel alone. "What makes this particularly concerning is that we found evidence these parasites can co-occur with other tick-borne pathogens," said Dr. Verocai, my co-author and veterinary parasitologist.

This means a single tick bite could potentially transmit multiple disease agents. One of the biggest obstacles I encountered in my research was the difficulty of finding these parasites. Traditional methods involve dissecting ticks under a microscope—labor-intensive work where it's easy to miss smaller larvae.

Modern techniques like DNA sequencing can detect parasite genetic material, but they can't tell if the parasite is alive or just remnant DNA from a blood meal.

"Each method has its strengths and limitations," I noted in our , which appears in Parasites & Vectors. "We need to combine these approaches to get a complete picture of what's really going on inside ticks."

Advanced imaging like micro-CT scanning can create 3D maps of parasites inside ticks, but it's expensive and not widely available. We need all these tools working together to truly understand what's happening inside ticks.

Some days, when I'm hunched over a microscope or wrestling with data analysis, I wonder why I chose to study something most people find revolting. Then I remember the bigger picture. Climate change is expanding tick habitats. Urban sprawl brings wildlife—and their parasites—into closer contact with pets and people. We're creating perfect conditions for emerging diseases, yet we're flying partially blind.

Every parasite we identify, every transmission cycle we map, every detection method we improve brings us one step closer to protecting the animals we love. That German Shepherd playing in your backyard, the white-tailed deer in state parks, even the cattle on Texas ranches—they all deserve our vigilance.

I believe Texas can lead the nation in tick-borne disease surveillance. We have the expertise, diverse ecosystems to study, and unfortunately, plenty of ticks to examine. Our review makes several key recommendations:

• Include filarial nematode screening in existing tick monitoring programs
  
• Develop practical diagnostic tools for veterinarians
  
• Conduct systematic surveys across Texas and North America
  
• Investigate how these parasites interact with other tick-borne diseases
  
• Study the health impacts of these infections in animals

You don't need a Ph.D. to make a difference. If you're a pet owner, maintain regular tick prevention and save any ticks you find for identification. If you're a veterinarian, consider filarial nematodes when typical tick-borne disease tests come back negative.

If you're a student, know that there's still so much to discover in this field. Science isn't just about making discoveries—it's about asking the right questions. My research showed me that when it comes to ticks and their hidden passengers, we haven't been asking nearly enough questions. The next time you find a tick, remember: that tiny arachnid might be carrying more than you think.

This story is part of , where researchers can report findings from their published research articles. for information about Science X Dialog and how to participate.

My name is Oluwaseun Ajileye. I am a PhD student in the Ecology and Evolutionary Biology Department at Texas A&M University, under the supervision of Dr. Jessica Light. I graduated with a bachelor's degree in Biology (parasitology), where I focused on characterizing and isolating medically important parasites and pathogens associated with humans and wildlife. My research now centers on the complex dynamics of host-parasite interactions and vector-borne diseases. I am particularly interested in investigating the distribution and coinfection patterns of filarial nematodes and tick-borne pathogens in North American tick vectors, employing next-generation sequencing and advanced molecular techniques to characterize tick microbiomes and elucidate the biological associations between vectors, parasites, and pathogenic microorganisms.