Human Babesiosis: Pathogens, Prevalence, Diagnosis, and Treatment

Abstract

Human babesiosis is a zoonotic disease caused by protozoan parasites of the Babesia genus, primarily in the Northeastern and Midwest United States due to B. microti, and Western Europe due to B. divergens. Parasites are transmitted by the bite of the ixodid tick when the vector takes a blood meal from the vertebrate host, and the economic importance of bovine babesiosis is well understood. The pathology of human disease is a direct result of the parasite’s ability to invade host’s red blood cells. The current understanding of human babesiosis epidemiology is that many infections remain asymptomatic, especially in younger or immune competent individuals, and the burden of severe pathology resides within older or immunocompromised individuals. However, transfusion-transmitted babesiosis is an emerging threat to public health as asymptomatic carriers donate blood and there are as yet no licensed or regulated tests to screen blood products for this pathogen. Reports of tick-borne cases within new geographical regions such as the Pacific Northwest of the US, through Eastern Europe, and into China are also on the rise. Further, new Babesia spp. have been identified globally as agents of severe human babesiosis, suggesting that the epidemiology of this disease is rapidly changing, and it is clear that human babesiosis is a serious public health concern that requires close monitoring and effective intervention measure.

SevereBabesia microtiinfection presenting as multiorgan failure in an immunocompetent host

“…Overall, a definitive diagnosis of babesiosis is commonly made by microscopic identification of the parasite on thin blood smears with Wright or Giemsa staining. However, among patients with low-grade parasitaemia, PCR assay represents a more sensitive diagnostic tool 10. In the present case report, the diagnosis of babesiosis was made by identification of the parasite in the peripheral smear.…”

Molecular Detection and Characterization of Zoonotic and Veterinary Pathogens in Ticks from Northeastern China

“…Approximately 100 Babesia species have been identified to infect a broad range of animals, in which malaria-like disorders are induced (Rozej-Bielicka et al, 2015). Babesiosis has a great effect on the animal production and on companion animals; however, human babesiosis has attracted increased attention (Ord and Lobo, 2015). In immunocompetent individuals, the infection is usually asymptomatic, or shows mild, self-resolving symptoms, but babesiosis can be life-threatening in neonates/infants, elderly persons, asplenic patients, and the immunocompromised populations (Fang et al, 2015; Ord and Lobo, 2015).…”

Splenic infarction in babesiosis: A rare presentation

“…Less common symptoms associated with mild disease include anorexia, depression, headache, neck stiffness, nonproductive cough, vomiting, and dark urine. On physical examination, hepatosplenomegaly, jaundice, and retinal infarction may be detected . Our patient demonstrated a number of these constitutional symptoms along with left upper quadrant abdominal tenderness and a syncopal episode.…”

“…However, this finding is not specific for Babesia , as the rings resemble those associated with intraerythrocytic Plasmodium trophozoites. A rare pathognomonic finding on peripheral blood smear is the occurrence of a Maltese cross (tetrads of immature merozoites) . Parasitemia can also be determined from peripheral blood smears, with levels rarely exceeding 5% in immunocompetent individuals but increasing to ≤85% in severe disease .…”

“…Polymerase‐chain reaction testing is more sensitive than peripheral blood smear and may be used in cases where the diagnosis is indeterminate . Serology via an indirect immunofluorescence assay for Babesia ‐specific immunoglobulin (Ig)M and/or IgG antibodies may also be used to support the diagnosis …”