Babesia duncani emerges in Eastern U.S. and may go undetected

The tick-borne illness Babesia duncani (B. duncani) was initially identified in the western regions of the United States. The disease has always been presumed to be confined to the West Coast, while its counterpart – Babesia microti (B. microti) has been well established on the East Coast.


New research indicates, however, there may no longer be a division of babesial strains between the East Coast and the West Coast. In their article “Babesia microtiBorrelia burgdorferi Co-infection,” Parveen reports that B. duncani has now been identified in eastern USA and Canada.¹

“Since B. duncani is widespread in Canada, its southern spread into northeastern U.S., an area already endemic for Lyme disease, makes co-infections with B. duncani and B. burgdorferi [Lyme disease] a possibility that needs to be carefully investigated.”

“While this review focuses on co-infection with B. microti and B. burgdorferi, there is some evidence that co-infections with a different Babesia species, B. duncani, and B. burgdorferi may be more common than previously suspected,” writes Parveen.

Babesia duncani emerges as a threat on the East Coast and in Canada. Click To Tweet

The authors raise concerns regarding treatment given that, “Antibiotics used against B. microti are less effective against B. duncani, making treatment of B. duncani potentially more challenging.”

“Clinical cases caused by Babesia duncani have been associated with high parasite burden, severe pathology, and death,” writes Abraham in The Journal of Biological Chemistry²

Animals fared worse. “In both mice and hamsters, the parasite causes uncontrolled fulminant infections, which ultimately lead to death,” writes Abraham.

Treatment for B. microti was not as effective for B. duncani in vitro culture, explains Abraham.

“Using this in vitro culture assay, we found that B. duncani has low susceptibility to the four drugs recommended for treatment of human babesiosis, atovaquone, azithromycin, clindamycin, and quinine.”

“These data suggest that current practices are of limited effect in treating the disease [B. duncani],” writes Abraham.

Editor’s note: I have diagnostic concerns. B. duncani is not routinely tested for in Canada and the Eastern USA. Individuals with B. duncani may go undiagnosed.

  1. Parveen N, Bhanot P. Babesia microti-Borrelia Burgdorferi Coinfection. Pathogens. 2019 Jul 31;8(3). pii: E117. doi: 10.3390/pathogens8030117. Review.
  2. Abraham A, Brasov I, Thekkiniath J, Kilian N, Lawres L, Gao R, DeBus K, He L, Yu X, Zhu G, Graham MM, Liu X, Molestina R, Ben Mamoun C. Establishment of a continuous in vitro culture of Babesia duncani in human erythrocytes reveals unusually high tolerance to recommended therapies. J Biol Chem. 2018 Dec 28;293(52):19974-19981.

17 Replies to "Babesia duncani emerges in Eastern U.S. and may go undetected"

  • Joseph Hein
    07/10/2022 (3:53 pm)

    Dx with B. Duncani, Bartonella, and Lyme. It’s been over a year with no relief from Chronic Fatigue, Peripheral Neuropathy and Anemia. Been on Zithromax, Mepron, Mamaroneck for 8 weeks and Bactrim for 3 weeks. No improvement, only getting worse. See Hematologist next week.

  • Kathleen
    03/04/2022 (8:43 pm)

    My husband pulled a tick off of him in October. 2 weeks later he scheduled an appt. with his PCP to get a Lyme test. His doctor took a look at him and sent him to the ER, where he was admitted as an inpatient for five days due to the fact he was in liver failure. The second day of his hospital visit I asked the team to test him for babesiosis. After 10 hours of advocating for this test and telling them the test needed to be sent to a speciality lab, the did test him, but in their own lab. His test came back negative.

    We have been going through four months of pure hell with his team of doctors dismissing the idea of him having babesiosis, so I purchased a kit from It came back positive for babesia duncani on Feb 23rd. We were finally validated and he was referred to an infectious disease specialist who did not see the specialty lab results, only the initial negative ones, and told us he was sure my husband did not have babesiosis. When he finally received a copy of the positive lab results, he was surprised and wanted to know how my husband “picked up a West coast parasite”. After telling him we did not travel to the west coast and that he was bitten by a tick in our back yard in New Hampshire, he finally prescribed us with the treatment for babesiosis, but STILL thinks the liver failure and the babesiosis are not related.

    This has been beyond frustrating and it feels like we are fighting for his life daily and no one will treat this seriously.

    I’m just here to share this story and see if anyone else in the NH area has experienced something like this. According to what I have read babesia duncani has been on the East coast since approx. 2018. How are doctors here not up to date on babesiosis??

  • Meg
    11/11/2021 (9:02 pm)

    How long do you typically treat? I tested positive for B. Duncani recently (Virginia) with no other parasite found. It’s complicated by chronic reactivating EBV. My doctor initially prescribed hydroxychloroquine, atovaquone, and azithromycin (21 days on, 10 days off x 3 cycles). I have found I’m completely intolerant to the hydroxychloroquine, so that’s been removed. Herx is tough on this. Is there anything I should ask in regard to other research? I haven’t found mych except for this site.

    • Dr. Daniel Cameron
      11/13/2021 (8:34 am)

      I find every patient in my practice challenging. I have not supported pulse or cyclical therapy.

  • Shari Damaso
    01/02/2021 (10:45 am)

    So what is an effective treatment for Babesia Duncani?

    • Dr. Daniel Cameron
      01/03/2021 (7:58 am)

      I start my patients with the same medications I use for Babesia microti e.g. azithromycin and atovaquone. I hope this research into Babesia duncani offers new insights.

    • Dan
      03/07/2022 (12:31 am)

      I’m from PA and experienced a very similar situation as you, but that seems to be the norm when dealing with infectious disease specialists and tick borne diseases. I’ve always been really fit and healthy, then some strange things started happening out of nowhere that ramped up over a 3 year period. Then one day I developed severe afib, and was off to the hospital by ambulance. A huge list of other symptoms grew from there (POTS, panic attacks, sweats, palpitations, head pain, unstable BP, tinnitus, air hunger, fevers, vertigo, etc.). I’m not sure how I survived summer 2020. Eventually I came to terms that the medical system wasn’t going to help me, and turned to my own research. I sincerely thank Dr. Daniel Cameron and Dr. Wayne Anderson for putting babesia on my radar, as I had never heard of it before… but their articles made more sense of my symptoms than anything else I was considering (cancer, lupus, MS, brain tumor, etc.). The information they posted may have very well saved my life. My condition progressively worsened, and I was several weeks bedridden before finally starting treatment with an LLMD. Initial IGeneX testing showed positive for Lyme and babesia sp. were visible on blood smear but no microti or duncani antibodies were detected. Within 3 days of starting malarone + azithromycin, I was 50% better and could start walking around the house… and start interacting with my wife and young kids again. Unfortunately, after about 2 months the malarone effectiveness seemed to decrease, and at 4 months it was obviously not working anymore. I was switched to primaquine, hydroxychloroquine, tinidazole (4 days on, 3 days off), and ceftin. I stayed on that combo for 6 months and my issues resolved one by one… and stayed gone. Babesia became undetectable on (>30 minute) blood smear inspections, but repeat IGeneX testing now showed positive IgG antibodies for duncani. The Lyme ImmunoBlot turned negative. New IGeneX testing showed I also have IgM and IgG antibodies to bartonella, and my RTL urine test was highly positive for multiple types of mycotoxins… so I still have some things to deal with. Today I’m feeling about 90% recovered… but some milder head pain, tinnitus, and intermittent vertigo remain. Babesia duncani was my worst infection, and it was a huge fight beating it back. If your ID docs in NH are like the ones in PA… I can’t stress strongly enough the importance of finding a good LLMD.

      BTW, my liver was affected by this. I was diagnosed with NAFLD with no plausible explanation. The liver damage even showed up on my first CT scan the day of afib. Follow up testing showed my liver is now completely healed after a year of treating tick borne infections.

  • Joel P.
    01/23/2020 (4:12 pm)

    I have been diagnosed with B. Duncani twice. I live in NYC, travel north on the summer only. I believe I’ve had it with me for many years & is only showing it’s ugly face now. Seem to be responding to Malarone & Mepron, but symptoms come back within 36 hours of stopping the medication. Doing this for 3 months.

    • Dr. Daniel Cameron
      01/23/2020 (8:17 pm)

      I have a similar experience in some patients in my practice.

      • Joel P.
        03/05/2020 (3:27 pm)

        How are you treating Duncani if Malarone & Mepron dont seem to kick it?

        • Dr. Daniel Cameron
          03/05/2020 (7:59 pm)

          I have had the same issues with Babesia microti. Sometimes I need to make sure other tick-borne infections are being treated. I have to make sure there is no other illness. I have tried clindamycin and quinine in a few cases. I have always had an interest in Flagyl or Tindamax as they work for parasites.

          • Henry
            03/28/2020 (7:52 pm)

            I tested positive for Babesia Duncani and I believe I contracted it in Northern VA. My doctor have me do 30 days of Mepron and Azithromycin. I then did 3 days of heavy Tinidazole/Tindamax. Im now starting my 2nd round of Mepron and Azithromycin. Has anyone had success with this regiment?

        • Angela
          01/11/2021 (5:33 pm)

          I’m wondering the same thing.
          My daughter is 12 and has tested positive for b.duncani. She was born in Fl and we have lived in NC since she was 5 months old. We have never been to the west coast so it’s definitely in the east. I’m looking for a good LLD here. She has also tested positive for borrellia miyamotoi.

    • Eric
      09/20/2020 (8:41 am)

      How are you doing now Joel? I start treatment tomorrow for same thing

  • Lynn
    11/09/2019 (1:29 am)

    I was once tested for Babesia duncani at a California Dept of Public Health Lab. Everyone was shocked it came back positive given I’d been infected on the East Coast. The lab director who seemed quite competent swore up and down that this test is accurate and that duncani is a very different species than microti (true). He said there couldn’t possibly be cross reactivity between the two organisms. I did find him believable. The test was repeated and came back positive again. This was back around 2001, so arguably I must have been one of the early victims of this parasite. But if you are looking for a test for this, you might look to the California Dept of Public Health Lab.

  • Beth
    10/23/2019 (3:07 am)

    Is the test for b. ducani reliable?

    • Dr. Daniel Cameron
      10/23/2019 (1:25 pm)

      I have my concerns. I have not seen reliability data in actual practice.

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