Babesia: Introduction, Morphology, Pathogenecity, Laboratory Diagnosis and Treatment

Introduction of Babesia: Babesiosis is caused by microscopic parasites, Babesia that infect red blood cells and are spread by ticks(Ixodes scapularis).  There is more than 100  species of Babesia , among them common are – B. microti, B. bovis , B. divergens. Named after Babes who first observed in blood of cattle and sheep. Tick borne disease which is most common in USA and Europe.

Introduction of Babesia

Babesiosis is caused by microscopic parasites, Babesia infects red blood cells and is spread by ticks(Ixodes scapularis).  There are more than 100  species of Babesia, among them common are –

B. microti,

B. bovis ,

B. divergens.

Named after Babes who first observed in the blood of cattle and sheep. Tick-borne disease is most common in the USA and Europe.

Scientific classification

  • Domain: Eukaryota
  • (unranked): Diaphoretickes
  • Clade: TSAR
  • Clade: SAR
  • Infrakingdom: Alveolata
  • Phylum: Apicomplexa
  • Class: Aconoidasida
  • Order: Piroplasmida
  • Family: Babesiidae
  • Genus: Babesia


Inside red blood cells (RBCs)

Morphology of Babesia

It has two forms and they are sporozoite and trophozoite.

Sporozoite: It is an infective form, found in ticks.


  • Oval and spindle-shaped having a size of 1 -5 µm.
  •  Small chromatin dot and scanty cytoplasm

Merozoites: They are oval or round present as pyriform bodies arranged in pairs or multiples of 2.

Life Cycle of Babesia

  1. Definitive host: Ixodes scapularis (tick)
  2. Intermediate host: Man and domestic animals

Pathogenicity: They can cause severe complications like-

  1. Acute tubular necrosis
  2.  Pulmonary oedema
  3.  Respiratory failure

Clinical features

Incubation period: 1 -4 weeks

  •  Fever
  • Mild splenomegaly
  • Anaemia
  •  Jaundice
  • haemoglobinuria


  • Haemolytic anaemia
  • WBC count;-normal or decreased
  • Reticulocyte count:-increased
  • Thrombocytopenia
  • ESR:-increased

Risk factors of Babesiosis

Following are the risk factors-

  1. People without spleen
  2.  weakened immune system
  3.  Older adults, especially those with other health problems

Laboratory Diagnosis

  • A thin and  thick smear
  • Stain: Leishman, Wrights and Giemsa
  • Only ring form seen


  1. Haemozoin and gametocyte are absent
  2. Merozoite arranged in tetrads or maltese cross form

Serodiagnosis:  Immunofluorescence assay (IFA)

Molecular Test: PCR

Other Tests

  • Serum protein electrophoresis:-poly clonalgammapathy
  • Urine:-haemoglobinuria and proteinuria
  •  Haptoglobin:-decreased


Babesia is a parasite that can not respond to antibiotics alone. Treatment requires antiparasitic drugs, such as those used for malaria and thus a combination of antimicrobial agents are used to treat them. Combination of clindamycin (600 mg 3 times daily)  and oral quinine 20 mg/kg body weight daily for children; 650 mg 3-4 times daily for adults. Medication is for 7-10 days.


  1. Babesiosis often occurs at the same time as Lyme disease. The tick that carries the Lyme bacteria can also be infected with the Babesia parasite.
  2. Babesia microti is the most common strain to infect humans, according to the Centers for Disease Control and Prevention (CDC).
  3. Babesia is also called Nuttallia.

Further Readings

  4. Atlas of Medical Helminthology and protozoology -4th edn  -P.L.  Chiodini, A.H. Moody, D.W. Manser
  5. Merkel and Voge’s medical parasitology-9th edition.
  6. Parasitology: 12th edition By K. D. Chatterjee
  7. District laboratory practice in Tropical countries –Part-I.
    By Monica Chesbrough.
  8. Isenberg clinical microbiology procedures Handbook
    2nd edition. Vol. 2
  9. Medical Parasitology by Abhay R. Satoskar, Gary L. Simon, Peter J. Hotez and Moriya Tsuji
  10. Atlas of Human Parasitology, Lawrence R Ash, Thomas C. Orihel, 3 rd ed, Publisher ASCP Press, Chicago.
  11. Molecular Medical Parasitology. Editors: J. Joseph Marr, Timothy W. Nilsen, and Richard W. Komuniecki, Publisher Academic Press, an imprint of Elsevier Science.
  12. Topley &  Wilsons Principle of parasitology. Editors: M.T. Parker & amp; L.H. Collier, 8 th ed 1990, Publisher Edward Arnold publication, London.
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