Babesia odocoilei: First Report of Human Pathogen

In a new study, Scott et al. report the first detection of Babesia odocoilei in humans with Babesiois symptoms. This adds to the list of several Babesia species worldwide that are pathogenic to humans. In this study, it was also found that B. duncani cross-reacts with B. odocoilei, therefore patients in North America who test serologically positive for B. duncani, may actually be infected with B. odocoilei or another Babesia spp.

Read full article here:
Detection of Babesia odocoilei in Humans with Babesiosis Symptoms

Read more LDA articles on Babesiosis here.



Surveillance of Babesiosis in the US

New study summarizes human surveillance data from 2011-2018 in the United States for Babesia infections reported to the Centers for Disease Control and Prevention (CDC) through the National Notifiable Diseases Surveillance System (NNDSS). Data shows an increasing trend of reported Babesia cases (14,159 total) during this time period, with white men in the middle and elderly age groups most affected. Data also shows that the New England and the Mid-Atlantic regions of the US reported highest numbers of Babesia cases. 

Access to full article can be found here

Read more LDA articles on Babesia here. 

A Review of Human Babesiosis

Geographical distribution of human babesiosis. The darker the color, the more numerous cases there are. There are no reported cases in unfilled countries or regions.

In this newly published review, Emerging Human Babesisosis with “Ground Zero” in North America, authors address the geographic distribution of the human-infecting Babesia spp., their phylogenetic relationship, and their tick vector worldwide. Species reviewed for human infection include, but are not limited to, B. microtiB. divergensB. venatorumB. duncaniB. crassa, and two yet unnamed Babesia species needing further investigation.

Authors found that the number of human Babesiosis cases appearing in the literature has increased exponentially in the last 10 years. Babesiosis has been a nationally notifiable disease in the United States (US) since 2011. Though cases of Babesiosis have been reported from all continents except Antarctica,  the US leads the world in case numbers of human Babesiosis with more than 20,000 total cases reported since 2006.
The authors state several factors which may have contributed to this rapid increase in human case numbers of Babesiosis including increased awareness of the disease in the medical community, active monitoring and survey studies,  global warming,  transfusion transmissions and vertical transmission from an infected mother to child.


Read full text review here: Emerging Human Babesiosis with “Ground Zero” in North America

Read additional LDA articles on Babesia here


Babesiosis Cases Increasing According to Medicare Databases Study

A study by Mikhail et al in Open Forum Infectious Diseases, Feb. 2021, from 2006 to 2017 showed 19,469 beneficiaries had babesiosis recorded, a substantial increase. The highest states by rates were Massachusetts (62), Rhode Island (61), Connecticut (51), New York (30), and New Jersey (19). States previously considered nonendemic saw increases: New Hampshire, Maine, Vermont, Pennsylvania, and Delaware.

See details of study and rates at state and county level


Study Reveals Some Tick-Borne Pathogens Found in Fleas

Photo by CDC, Peromyscus leucopus

In a recent study conducted in central Pennsylvania, evidence of emerging pathogens, some also common to ticks, have been found in fleas. Various pathogens can be spread by ectoparasites among animal host populations in nature. Along with ticks, fleas are found to commonly infest small mammals. The role of pathogen transmission cycles for these vectors is unknown.

In this study, small mammals were captured and fleas were collected in an effort to better understand the enzootic cycle of flea‐borne pathogens in central Pennsylvania. Pathogen testing was conducted in both the small mammal hosts and the fleas collected. 

Seven species of small mammals were captured of which white‐footed mice (Peromyscus leucopus) and southern red‐backed voles (Myodes gapperi) accounted for over 94% of the captures. Only P. leucopus tested positive for the blood‐borne pathogens examined, with 47 (18.1%) positive for Anaplasma phagocytophilum and ten (4.8%) positive for Babesia microti.

Of the 61 fleas collected from small mammals and tested for pathogens,  Orchopeas leucopus was the most common flea species. Pathogenic bacteria and parasites were detected in 33.3% of total fleas collected, and included Bartonella vinsonii subspecies arupensisB. microti, and a Rickettsia felis‐like bacterium. Researchers believe this to be the first report of B. microti DNA detected from a flea, as well as the first report of a R. felis‐like bacterium from rodent fleas in eastern North America.

At this time, only plague (Yersinia pestis) is a nationally reportable flea-borne disease in the United States. Like tick-borne diseases, under-reporting of flea-borne illnesses limits understanding of the burden of disease from these vectors. The potential for new and re‐emerging pathogens in fleas as well as the potential for fleas to play a role in natural transmission cycles of tick‐borne pathogens is not understood. This study elucidates that further investigation is needed to understand the ecology of flea‐borne disease transmission cycles, vector competence of fleas for tick-borne pathogens, and the risk to human health.

Read full article: Host distribution and pathogen infection of fleas (Siphonaptera) recovered from small mammals in Pennsylvania



Babesiosis is a Malaria-like illness caused by a parasite, either Babesia microti, B. duncani, B. divergens, MO-1.

It is sometimes fatal in the elderly or those with no spleen.  Babesiosis may be more severe in patients with co-existing Lyme disease.

Symptoms include: fever, chills, fatigue, headache, muscle pain, sweats and anemia.

Tests for Babesiosis: blood smears, IFA (IgG & IgM), FISH (Flourescent in-situ Hybridization) and PCR may be ordered.*

* These tests were developed & performance characteristics determined by independent labs. They have not been cleared or approved by the FDA; however, the FDA has determined such clearance is not necessary. They are designd for clinical purposes and should not be regarded as investigational or for research.

Treatment is often atovaquone with azithromycin or clindamycin and oral quinine.  Treatments vary, examples provided as information only.

Ticks that transmit babesiosis include Ixodes Scapularis (also called blacklegged tick or deer tick) and Ixodes Pacificus (western blacklegged tick) both of which also transmit Lyme disease.  Multiple infections may be transmitted from the bite of the same tick.

Babesiosis has also been transmitted to humans through blood transfusions.  In 2018, the FDA approved a test to screen the blood supply for Babesia microti.  See: FDA Approves Tests to Screen Blood Supply for Babesia

Resources for transplacental transmission of Babesia:

1. Fox, L.M.; Winger, S.; Ahmed, A.; Arnold, A.; Chou, J.; Rhein, L.; Levy, O. Neonatal babesiosis: Case report and review of the literature. Pediatr. Infect. Dis. J. 200625, 169–173.

2. Cornett, J.K.; Malhotra, A.; Hart, D. Vertical transmission of babesiosis from a pregnant, splenectomized mother to her neonate. Infect. Dis. Clin. Pract. 201220, 408–410.

3. Iyer, S.; Goodman, K. Congenital babesiosis from maternal exposure: A case report. J. Emerg. Med. 2009, 56, e39e41.

4. Khangura, R.K.; Williams, N.; Cooper, S.; Prabulos, A.M. Babesiosis in pregnancy: An imitator of HELLP syndrome. AJP Reports 2019, 9, e147e152.

©LDA.  2014.  2015. This web site provides practical and useful information on the subject matters covered. It is distributed with the understanding that LDA is not engaged in rendering medical or other professional services. Seek professional services if necessary.