Overall annual incidence rose from 0.6 to 0.9 cases per 100,000 in the United States between 2012 and 2015 (Gray 2019)
Annual incidence is highest in those between 60-69 years of age (Gray 2019)
Age:
Median age is 63 years of age with greater than 89% of cases reported in Caucasian patients (Gray 2019 2010)
Gender:
Male to female predominance (Gray 2019)
Morbidity/Mortality:
Overall hospitalization rates for confirmed cases are noted to range from 16% to 72.6% depending on the patient’s age (Gray 2019)
Mortality rates up to 10% have been noted in hospitalized patients (Vannier 2015)
Mortality rates are much higher among immunocompromised patients and those who acquired the illness through blood transfusion
Geography and Seasonality (Gray 2019): Cases predominately in the Northeastern and Upper Midwestern United States
Seven States account for over 94% of all reported cases:
New York
Massachusetts
Connecticut
New Jersey
Rhode Island
Wisconsin
Minnesota
Seasonal distribution is concentrated in June, July, and August
Poor Prognostic Factors (Vannier 2015):
Neonates and > 50 years of age
Coinfection with Lyme Disease
Immunocompromised states
Delays in diagnosis and treatment
Asplenia
Pathogenesis (Krause 2019):
After tick transmissibility, Babesia species, an intraerythrocytic protozoa, will mature, replicate, and release into the bloodstream to invade nearby red blood cells
This infection leads to erythrocyte lysis, metabolic alterations, proinflammatory cytokine production, and obstruction of blood vessels
History and Physical:
Symptoms (Vannier 2015):
Symptoms typically appear 1-4 weeks after bite of an infected tick
Rash is not a common occurrence unlike other tick-borne illnesses
If present, it should raise the suspicion for co-infection with Lyme disease
Fever occurs in 89% of recognized cases of babesiosis along with other non-specific flu-like symptoms:
Fatigue
Chills
Headache
Anorexia
Myalgia
Emotional liability and depression
Gastrointestinal symptoms are often seen
Physical Examination:
Mild splenomegaly and hepatomegaly are sometimes found on examination
Jaundice and dark urine are sometimes found on examination due to intravascular hemolysis
Severe Manifestations: Most cases are self-limiting, but Babesiosis has been associated with the following severe disease manifestations:
ARDS
Renal Failure and Hepatic Failure
Rhabdomyolysis
DIC
Heart Failure
Coma
Splenic Rupture
Hemophagocytic Syndromes
Diagnosis:
Labs: Characteristic laboratory findings are seen in Babesiosis along fever and non-specific flu-like illness:
Thrombocytopenia
Hemolytic Anemia
Low Haptoglobin Level
Elevated Reticulocyte Count
Elevated LDH Level
Elevated Indirect Bilirubin and Mildly Elevated Hepatic Transaminase
Blood Smear (Vannier 2015):
Diagnosis can be made with visualization of Babesia parasites on Giemsa or Wright stained thin blood smears.
The level of parasitemia is typically between 1 and 10% but can be as high as 80% in severe disease.
Babesia species sometimes exhibit the presence of tetrads (Maltese cross) and have the absence of hemozin deposit in the ring form as well as lack banana-shaped shaped gametocytes, thus distinguishing them from plasmodia species.
Confirmatory Testing:
Serological testing of IgM and IgG antibodies specific to Babesia species using indirect immunofluorescence assay (IFA) is available for confirmation.
RT-PCR assays are also available for diagnosis of Babesiosis with have high sensitivity and specificity.
Guest Post By:
Akash Ray, DO
PGY-2 Emergency Medicine Resident Inspira Medical Center
Vineland, NJ Twitter:@_kashray
References:
Biggs H et al. Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis – United States. MMWR Recomm Rep. 2016. PMID: 27172113
Gray E et al. Babesiosis Surveillance – United States, 2011-2015. MMWR Surveill Summ. 2019. PMID: 31145719
Vannier E et al. Babesiosis. Infect Dis Clin North Am. 2015. PMID: 25999229
Krause P. Human babesiosis. Int J Parasitol. 2019. PMID: 30690090
Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)
