Babesia, Blood Parasite Exam (LAB7012)

Babesiosis is caused by Babesia spp., which are parasites that infect red blood cells.  Infection occurs following the bite of an infected Ixodes tick.  Symptoms typically occur within 1-4 weeks after the tick bite and may include fever, malaise, chills, sweats, headaches, and body aches.  A notable complication of babesiosis is hemolytic anemia, and infection may be more severe in asplenic patients, immunocompromised patients, and the elderly.    

Babesiosis is most common in the Northeastern United States and upper Midwest. Babesia infections are rare in Missouri with 0-1 cases reported each year statewide. 

The gold standard for diagnosis is a blood parasite exam (LAB7012), which is performed in-house, resulted within 24h, and provides a percent parasitemia to guide management and monitor response to treatment.  Three smears are recommended at various intervals to rule-out Babesia, as parasitemia may be sporadic.  

• Given the near absence of babesiosis cases in Missouri, testing is only recommended for patients with recent travel to endemic regions. 
• Antibody testing is not recommended for diagnosis. For recently symptomatic individuals, antibodies may not yet have developed. 
• Nucleic acid testing (PCR) for Babesia is performed at reference laboratories and has been reported to be as sensitive as blood smears.  However, results from these tests are qualitative and cannot be used to quantitatively monitor patient response. 

• Babesia is not a common tick-borne pathogen in Missouri, with 0-1 cases reported statewide each year.  The most common tick-borne pathogens for patients from Missouri are Ehrlichia spp. (Ehrlichiosis) and Rickettsia rickettsii (Rocky Mountain Spotted Fever). 
• Laboratory diagnosis of babesiosis is made via a microscopic blood parasite examination, which is rapid and quantitative.  Antibody testing and PCR are not recommended for routine diagnosis.

1. Centers for Disease Control and Prevention. 2017.  Babesiosis. Available at: https://www.cdc.gov/dpdx/babesiosis/index.html. 
2.  Centers for Disease Control and Prevention. National Notifiable Diseases Surveillance System, 2020 Annual Tables of Infectious Disease Data. Atlanta, GA. CDC Division of Health Informatics and Surveillance, 2023. Available at: https://www.cdc.gov/nndss/data-statistics/infectious-tables/index.html. 
3. Krause PJ, Telford S 3rd, Spielman A, et al. Comparison of PCR with blood smear and inoculation of small animals for diagnosis of Babesia microti parasitemia. J Clin Microbiol. 1996;34(11):2791-2794. doi:10.1128/jcm.34.11.2791-2794.1996