Babesiosis - A guide to babesiai infection)

Caused by haemoprotozoan parasites from the genus of Babesia, Babesiosis is another term for Babesia Infection. There are over one hundred species of Babesia, but fortunately, only a few of them are known to infect humans. The most common species to cause disease in humans is Babesia divergens and Babesia microti. Babesia are often mistaken to be Plasmodium in malaria endemic locations.

The life cycle of the Babesia microti requires two hosts. The first host is a tick. Inside the tick, gametes collect and enter the sporogonic cycle, creating sporozoites to infect the next host with. A tick infected by the Babesia feeds on a mouse host, introducing sporozoites into the rodent. The sporozoites begin the budding stage by entering erythrocytes, reproducing asexually. Although the distinction cannot be made easily, even with a light microscope, the parasites do separate into female and male gametes as they enter the blood.

Vertical or hereditary transmission, also referred to as transovarial transmission is not common for Babesia microti, but has been known to occur for other species of Babesia. Babesiosis occurs in humans when humans are occasionally bitten by infectious ticks. Humans experience symptoms when parasites multiply in the blood. However, humans are rarely suitable hosts for the various types of Babesia and transmission from tick to human is extremely rare. However, there have been reports of Babesiosis spreading from person to person due to blood transfusions. 

While Babesia have been found all over the world, it is difficult to document the occurrence of Babesiosis in areas impacted by malaria because in such areas, Babesia can be mistaken as Plasmodium. Babesia divergens is known to cause most European cases, especially in splenectomized individuals. Meanwhile, Babesia microti is more common in the United States and does not seem to especially impact splenectomized patients. There have been variants of the Babesia microti parasite, considered altogether different species, in California, Missouri, and Washington.

The clinical features of Babesiosis may be sweating, fever, chills, fatigue, hepatosplenomegaly, haemolytic anaemia, and myalgias. However, most cases of Babesiosis display no symptoms according to serologic surveys and when symptoms do occur, it takes an incubation period of up to four weeks for them to surface. Symptoms may last several weeks and are more severe in splenectomized, elderly, or immunosuppressed patients. While instances of Babesia microti infection are relatively easy to recover from, cases caused by the Babesia divergens are more severe and can be fatal without appropriate treatment. 

Babesiosis is diagnosed by examining thin and thick smears of blood stained with Giemsa. Microscopic examination of multiple smears along with detection of antibodies using indirect fluorescent antibody test work as diagnostic tests of Babesiosis. Babesiosis is treated with atovaquone and azithromycin working in combination. Another option is clindamycin and quinine in combination. In some instances, transfusion can help severely infected individuals experiencing a very high level of parasitaemias and consequent symptoms.