doi: 10.1097/MOH.0000000000000606. Online ahead of print.

Human babesiosis: recent advances and future challenges

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Purpose of review: As human babesiosis caused by apicomplexan parasites of the Babesia genus is associated with transfusion-transmitted illness and relapsing disease in immunosuppressed populations, it is important to report novel findings relating to parasite biology that may be responsible for such pathology. Blood screening tools recently licensed by the FDA are also described to allow understanding of their impact on keeping the blood supply well tolerated.

Recent findings: Reports of tick-borne cases within new geographical regions such as the Pacific Northwest of the USA, through Eastern Europe and into China are also on the rise. Novel features of the parasite lifecycle that underlie the basis of parasite persistence have recently been characterized. These merit consideration in deployment of both detection, treatment and mitigation tools such as pathogen inactivation technology. The impact of new blood donor screening tests in reducing transfusion transmitted babesiosis is discussed.

Summary: New Babesia species have been identified globally, suggesting that the epidemiology of this disease is rapidly changing, making it clear that human babesiosis is a serious public health concern that requires close monitoring and effective intervention measures. Unlike other erythrocytic parasites, Babesia exploits unconventional lifecycle strategies that permit host cycles of different lengths to ensure survival in hostile environments. With the licensure of new blood screening tests, incidence of transfusion transmission babesiosis has decreased.


Rise in Babesiosis Cases, Pennsylvania, USA, 2005–2018

David Ingram; Tonya Crook

Emerging Infectious Diseases. 2020;26(8):1703-1709. 


Babesiosis is an emerging infection in the state of Pennsylvania, and clinicians need to be made aware of its clinical manifestations as well as the risk factors associated with severe disease. Before 2010, our tertiary academic center in central Pennsylvania previously saw zero cases of babesiosis. We saw our first confirmed case of Babesia infection acquired in Pennsylvania in 2011; we recorded 2 confirmed cases in 2017 and 4 confirmed cases in 2018. All 4 cases from 2018 were thought to be acquired in southcentral Pennsylvania counties, whereas prior reports of cases were predominately in the southeast and northeast counties of the state.



Out of 352 patients in the second study, some of which were duplicates, they reviewed patient charts and only identified 8 cases using CDC criteria.  This continues to be a problem as CDC testing misses many cases, and many do not meet the stringent criteria which in many cases is arbitrary.  The study also noted that there were inconsistencies in the way blood smears and PCR testing were ordered.  

Important to note: most were immunocompetent.

Symptoms(numbers in parenthesis show how many patients had it):

  • fever (6/8) 
  • malaise (5/8)
  • myalgias or arthralgias (2/8)
  • anorexia (2/8),
  • rash (1/8),
  • headache (1/8),
  • nausea or vomiting (1/8)
  • diarrhea (1/8)
  • respiratory failure (1/8)

The most common laboratory abnormalities:

  • anemia (seen in all patients)
  • thrombocytopenia (7/8)
  • transaminitis (7/8) – high liver counts can lead to liver damage
  • hyperbilirubinemia (7/8) excess bilirubin can cause jaundice
Importantly: concurrent Lyme disease was noted in half (4/8) of patients.

Patients were screened for Lyme disease by using ELISA; if the result was positive, then a Western blot was performed. Patients had Lyme disease diagnosed if they had positive ELISA results and positive IgM or IgG results on Western blot.

I can guarantee you more patients had Lyme but were omitted due to abysmal testing. This has been going on for over 40 years.

Six of the 8 patients were classified as having severe infection with parasitemia >10%. Four of the 6 patients with severe infection had co-infection with Borrelia burgdorferi (Lyme disease). The 2 nonsevere patients did not have co-infection.

This agrees with previous findings that concurrent infection makes for more severe disease for a longer duration of time:

  • Most (7/8) patients received a combination of azithromycin and atovaquone 
  • 3 received clindamycin and quinine.  Of these 3 patients, 1 patient received clindamycin and quinine alone for the duration of their therapy, and 2 patients were switched to azithromycin and atovaquone because of persistent parasitemia. Two of the patients who received clindamycin and quinine (1 of whom was switched to azithromycin and atovaquone) also required blood or platelet transfusions. Five patients underwent red cell exchange transfusions.
  • Average duration of treatment was 18.1 days. The average duration of parasitemia was 9 days.
  • They only had exact date of clearance for 3 of the 8 patients

The authors admit that due to focusing on specific Babesia-related codes, they probably missed patients that were co-infected.  

Once again they erroneously bring up the climate as a factor in tick expansion (therefore disease expansion).  This has been proven to be a faulty assumption:

They correctly state there is a steady rise in Babesia throughout the U.S.  They also state that the geographic spread could be favored by prior establishment of Lyme disease and that coinfection in mouse reservoirs increases Babesia transmission.

They also rightly maintain:

clinicians must maintain a high index of suspicion in patients with a nonspecific febrile syndrome despite absence of tick bite history or lack of an immunocompromising condition. Evaluation for co-infections, particularly co-infection with B. burgdorferi, should be considered given patients with co-infection appear to have more severe disease.

Herein lies the problem.  Testing for all of this remains abysmal.  Without accurate tests most doctors are just going continue to say, “It’s all in your head.”  And they will continue to get away with it.  

Most mainstream doctors are not even considering coinfection and continue to view this through a myopic tunnel-vision where they believe people are only infected with one pathogen.