Babesiosis

Babesiosis, also known as piroplasmosis, is a malaria-like parasitic disease caused by infection with eukaryotic parasites of the order Piroplasmida, typically belonging to the genus Babesia or Theileria within the phylum Apicomplexa. The causative agents are protozoan parasites that invade and reproduce within red blood cells, producing characteristic Maltese cross formations visible on blood smears. This places Babesia as the second-most common blood parasite of mammals after trypanosomes.

Approximately half of all children and a quarter of previously healthy adults with Babesia infection remain asymptomatic. When symptoms do occur, the most common manifestations are fever and hemolytic anemia, which closely resemble the clinical presentation of malaria. Symptomatic individuals typically develop illness 1 to 4 weeks after a tick bite or 1 to 9 weeks following transfusion of contaminated blood products. The disease course is characterized by progressive malaise and fatigue followed by fever, with additional common findings including chills, sweats, and thrombocytopenia. Symptoms may persist from several days to several months. The pathophysiology involves parasite-mediated destruction of red blood cells, leading to hemolytic anemia, though unlike Plasmodium parasites, Babesia species rarely exhibit an exoerythrocytic phase.

Human babesiosis transmission via tick bite is most common in the Northeastern and Midwestern United States and in parts of Europe, with sporadic occurrence throughout the rest of the world. The disease exhibits a seasonal pattern, occurring predominantly during warm weather months when tick activity is highest. Babesiosis often presents as a co-infection with other tick-borne illnesses such as Lyme disease, given shared vector exposure. The infection has major adverse effects on the health of domestic animals, particularly in regions without severe winters; in cattle, the disease is known as Texas cattle fever or redwater fever. Due to the specialized laboratory requirements for diagnosis, Babesia infections are considered highly under-reported globally.

Human infection with Babesia parasites occurs through three primary routes: the bite of an infected tick, receipt of contaminated blood products through transfusion, and congenital transmission from an infected mother to her fetus. Tick-borne transmission is the most common route in endemic areas, with the vector often carrying multiple tick-borne pathogens simultaneously. The potential for transfusion-transmitted infection is significant enough that even mild cases are recommended for treatment to prevent inadvertent blood donation transmission.

Individuals at increased risk for severe or symptomatic babesiosis include those who are immunocompromised, elderly, or asplenic. The presence of concurrent conditions such as Lyme disease may also increase susceptibility to symptomatic infection. Source-backed detail on additional high-risk groups is not yet available.

Source-backed detail on specific prevention measures is not yet available.

Babesiosis surveillance is complicated by the disease's nonspecific clinical presentation and the specialized laboratory capacity required for definitive diagnosis. The infection should be suspected in individuals with exposure history in endemic areas or who have received a blood transfusion within the preceding 9 weeks, particularly when presenting with persistent fever and hemolytic anemia. Definitive diagnosis requires identification of parasites on a Giemsa-stained thin-film blood smear, with the characteristic Maltese cross formation being pathognomonic for babesiosis. Given these diagnostic challenges, reported case numbers likely represent substantial underestimation of true disease burden.

1. 1 Wikidata. Babesiosis.
2. 2 Wikipedia. Babesiosis - Wikipedia.

ICD-10

ICD-11

Total cases

8K

Peak month

2023-07

Coverage

1 reporting countries · 2014-01-18 → 2024-12-28