Babesia

Overview
  • Babesia refer to a large genus of protozoa which can infect humans but whose natural reservoir are a variety of wild and domestic mammals. Babesia are spread by tick arthropod vectors and are present in the Northeast US and in Europe. Although a less serious disease, the basic clinical consequences and pathogenesis of Babesiosis is similar to that of Malaria.
Life Cycle
  • Inoculation occurs during a blood meal from an infected tick which deposits the "Sporozoite" form of the organism in the blood. The motile sporozoites infect erythrocytes and replicate by progressing through "Trophozoite" and "Schizont" forms, similar to plasmodial species, and then mature into "Merozoites". Mature merozoites lyse erythrocytes and can infect other erythrocytes or differentiate into gametocytes which can be taken up once again by the tick vector.
Diagnosis
  • Diagnosis of babesia is performed by giemsa-staining of peripheral blood smears where infected erythrocytes can be detected. Uniquely, babesial replication within erythrocytes results in only four merozoites which take on a pathognomonic tetrad arrangement similar to a "Maltese Cross". Circular trophozoite ring forms can also be observed as in plasmodium-infected erythrocytes.
Clinical Consequences
  • Infection with babesia is often subclinical. When clinical consequences emerge they are primarily nonspecific constitutional symptoms such as fever, chills, myalgia, headache, and malaise. Complications can arise in those who are chronically ill but this is uncommon among healthy individuals. Asplenic patients are at a higher risk of infection and the severity is intense and potentially life-threatening.
Treatment
  • Mild infections are treated with azithromycin. Severe infections are treated with quinolines such as quinine and clindamycin.