August 27th, 2025

Lyme Disease, Parasites, &
The Overlooked Co-Infections

When most people think about Lyme disease, they think of bacteria. It is true that Lyme is caused by the spirochete Borrelia burgdorferi, which is a parasitic bacterium. Like other obligate parasites, it cannot live freely in the environment and depends on a host (tick, mammal, or bird) for survival and reproduction.

What often gets overlooked, however, is that ticks transmit more than bacteria. They also carry parasites and these co~infections can dramatically change the course of illness.

1. Ticks Carry Both Bacteria and Parasites

• The same Ixodes ticks that spread Borrelia can also transmit Babesia microti, a malaria-like protozoan parasite.
• The CDC recognizes co-infection with Lyme and Babesia in humans, especially in the Northeast and Midwest United States.
• This means a single tick bite can deliver both bacteria and parasites at once.

2. Co-Infections Worsen Disease Course

• Patients with Lyme + Babesia infections often experience more severe and longer-lasting symptoms than those with Lyme alone.
• Babesia infects red blood cells, leading to night sweats, fevers, and shortness of breath (“air hunger”) symptoms that are sometimes mistaken for “chronic Lyme.”
• A landmark study by Krause et al., NEJM 1996, confirmed that co-infected patients had worse outcomes and slower recovery.

3. Immune Evasion and Antigen Overload

• Borrelia hides from the immune system by changing its surface proteins (antigenic variation of the VlsE protein).
• Babesia and other parasites release antigens continuously into the bloodstream, keeping the immune system on high alert.
• Together, these infections create a heavy antigen burden that can drive chronic inflammation, immune suppression, and even autoimmune reactions.

4. Beyond Babesia: Other Tick-Borne Parasites

• Research shows Ixodes ticks act as multi-pathogen carriers, transmitting bacteria, viruses, and parasites together.
• While Babesia is the best-known parasitic co-infection in humans, other protozoa (like Theileria species) are also carried by ticks and infect animals, with occasional spillover into humans.
• Studies such as Tokarz et al., mBio 2019 confirm high rates of mixed infections in ticks.

5. Diagnostic Blind Spots

• Standard Lyme tests (ELISA, Western blot) only detect Borrelia antibodies and miss co-infections.
• Babesia is best identified through PCR testing or blood smears, but low level infections often go undetected.
• As a result, many patients treated with antibiotics for Lyme continue to suffer because the parasite infection remains untreated.

Key Takeaway

• It is well established that ticks transmit both Borrelia (Lyme bacteria) and Babesia (parasites).
• Peer reviewed research consistently shows that co-infections make Lyme disease more severe, longer-lasting, and harder to treat.
• The medical system largely focuses on the bacterial component and under-recognizes the parasitic burden, and leaving an important part of the illness unaddressed.

In other words: We fully understand and treat Lyme, people have to look beyond bacteria alone and recognize the role of parasites in the tick-borne disease complex. ~Mrs. Duplechain