When people think of tick bites, they usually think of Lyme disease. But the same tick can carry more than one germ. When a person is infected with Lyme disease and another tick-borne illness at the same time, it is called a co-infection.
Co-infections can make symptoms more severe, more confusing and harder to treat. At Immunotherapy Institute, we see many patients with persistent symptoms who have never been fully evaluated for them. In this guide, we explain the most common Lyme disease co-infections, how they differ and why a complete evaluation matters.
Why Co-Infections Happen
The blacklegged tick, also called the deer tick, is the main carrier of Lyme disease in the eastern US. According to the CDC, this tick can also transmit several other illnesses:
- Anaplasmosis.
- Babesiosis.
- Borrelia miyamotoi infection.
- Borrelia mayonii infection.
- Powassan virus disease.
A single bite can transmit more than one of these. That is why symptoms that do not fit a typical Lyme pattern deserve a closer look.
Babesia: A Parasite in the Red Blood Cells
Babesiosis is caused by tiny parasites that infect red blood cells. The CDC notes that Babesia microti is the most common species in the US, and most cases occur in the Northeast and upper Midwest.
Symptoms
Many people have no symptoms. Others develop flu-like symptoms such as fever, chills, sweats, headache, body aches, loss of appetite, nausea and fatigue. Because the parasite destroys red blood cells, it can cause hemolytic anemia.
Who Is at Higher Risk
The CDC lists people without a spleen, those with weakened immune systems, including from cancer or lymphoma, people with serious liver or kidney disease, and adults over 50. In these groups, babesiosis can become serious.
Diagnosis and Treatment
Babesia is usually diagnosed by examining a blood sample under a microscope or with specialized lab tests. Effective treatment is available, and it is different from the antibiotics used for Lyme disease. This is one reason why identifying co-infections is so important.
Anaplasma: The Most Common Co-Infection
Anaplasmosis is a bacterial infection that affects white blood cells. According to the CDC, it is the most common co-infection with Lyme disease, found in roughly 10% of Lyme patients. Symptoms often include fever, headache, chills and muscle aches. The good news is that doxycycline, a common Lyme antibiotic, also treats anaplasmosis.
Bartonella: Why It Is Debated
Bartonella is a group of bacteria best known for causing cat scratch disease. Many patients with chronic symptoms hear about it as a possible Lyme co-infection, so it is important to understand what the science says.
According to the CDC, Bartonella bacteria spread to people mainly through cat scratches, flea exposure, body lice and sand flies. The CDC states that there is no evidence showing Bartonella spreads to people through tick bites, although one laboratory study found transfer from ticks to animals and more research is needed.
Why does it still matter? Because some patients with long-lasting symptoms may have been exposed to Bartonella through other routes, such as pets. A thorough evaluation looks at your full history, not only at tick exposure.
Other Tick-Borne Infections
- Borrelia miyamotoi: a bacterium related to Lyme disease that can cause fever, chills and headache. Standard Lyme tests may not detect it.
- Powassan virus: rare, but it can cause serious illness, including inflammation of the brain.
Why Co-Infections Matter
They Can Make Symptoms Worse
Having two infections at once can lead to more severe or longer-lasting symptoms than Lyme disease alone.
They May Need Different Treatment
Some co-infections, like babesiosis, do not respond to the antibiotics used for Lyme disease. If a co-infection is missed, a patient may continue to feel sick even after completing Lyme treatment.
They Can Complicate Diagnosis
Lyme testing already has limits, as we explain in our guide on how Lyme disease is diagnosed. Co-infections add another layer, which is why a complete history and the right tests matter.
Signs You May Have a Co-Infection
- High fevers, sweats or chills that keep coming back.
- Unexplained anemia or very low energy.
- Symptoms that did not improve after standard Lyme treatment.
- Symptoms that seem more severe than expected.
- A history of tick bites in the Northeast or upper Midwest.
If any of these sound familiar, talk to your doctor about testing for tick-borne co-infections. Early answers can save months of frustration.
How We Evaluate and Support Patients
Many patients come to us after years of symptoms and incomplete answers. Our integrative assessment reviews your history, previous tests and treatments, and adds testing to better understand immune function and inflammation.
When co-infections have been treated but symptoms persist, our Lyme disease treatment program in Mexico focuses on immune balance and recovery. Depending on your evaluation, it may include:
- Autologous T-regulatory cell therapy, using your own immune cells.
- Therapeutic apheresis, a blood filtration process.
- Heckel hyperthermia, under medical supervision.
- Targeted IV therapy, such as glutathione and vitamin C.
- Detoxification and cellular nutrition support.
Learn more in our articles on immunotherapy for Lyme disease and Lyme disease treatment near San Diego.
Preventing Tick Bites
- Use an EPA-registered insect repellent when outdoors.
- Wear long sleeves and pants in wooded or grassy areas.
- Check your body, children and pets for ticks after being outside.
- Shower soon after coming indoors.
- Remove ticks promptly with fine-tipped tweezers.
Co-Infections and the Immune System
Fighting more than one infection at a time puts extra strain on the immune system. Babesia, for example, damages red blood cells and can leave patients deeply tired, while Anaplasma affects white blood cells that help fight infection. When several infections overlap, the body may take longer to recover, and inflammation can linger even after the germs are treated.
This is one reason we look at immune function and inflammation, not only at test results for each germ. Supporting immune balance can be an important part of recovery for patients who still feel unwell after treatment.
Frequently Asked Questions
Can one tick bite cause more than one infection?
Yes. The blacklegged tick can carry several germs, and one bite can transmit more than one.
Does Lyme treatment also treat co-infections?
Sometimes. Doxycycline treats anaplasmosis, but babesiosis needs a different treatment.
Is Bartonella a Lyme co-infection?
The CDC says there is no evidence that ticks spread Bartonella to people. It can still be worth evaluating in patients with other exposures, such as cats or fleas.
Should I be tested for co-infections?
If your symptoms are unusual, severe or did not improve with Lyme treatment, ask your doctor about testing.
Can you help if my co-infections were already treated?
Yes. Our program is designed for patients who still have symptoms after standard treatment.
Get a Complete Evaluation
If your recovery has stalled, the missing piece may be something no one has looked for yet. Our team will review your full history and help you understand your next steps. Bring your previous test results, and we will look at the full picture together.
Request your free case review, call us at (619) 832-2230, or message us on WhatsApp. We respond within 24 hours.
This article is for educational purposes and does not replace medical advice. Individual results vary.