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Life Cycle of Babesia

Plasmodium, more commonly called malaria, and babesia are common parasites that affect both humans and animals. Common names for babesia include redwater fever, piroplasmosis and babesiosis. Similar to malaria, babesia lives and reproduces inside the circulatory system organs and red blood cells.

  1. What is Babesia?

    • Babesia are parasites. They live inside the blood cells of vertebrate hosts where they commonly exist as pairs, but reproduce asexually. Ticks transmit the disease, which very strongly resembles malaria.

    Hosts and Habitat

    • Most cases of babesia occur in wild and domestic mammals including dear, rodents, cattle and dogs. The white-footed mouse serves as the primary reservoir of the disease, and the deer tick is the main carrier. Up to 60 percent of mice can be infected in areas considered endemic. Lab experiments show that nearly all infected mice produce infected ticks.

    Reproduction

    • The life cycle begins when the infected tick injects sporozoites into a mouse while eating its blood. The sporozoites travel to red blood cells and begin to asexually reproduce by budding. Next, they split into male and female gametes that are once again eaten by the tick. Inside the tick, the gametes join to produce sporozoites--a sporelike stage that is the infective agent introduced into a host. The incubation period lasts from 1 to 6 weeks.

    Life Cycle Steps

    • First, the sporozoites travel to the red blood cells of the host where they change to trophozoites (the growing stage). Next, during schizogony--asexual reproduction--two and then four divisions develop as the parasites split. While still in the blood cells, the parasites are ingested by ticks eating the host's blood. They move into the tick's gut cells and ingest bacteria or other material (phagocytosis) which transforms them into phagocytes as the tick passes through its larval stage to the nymph stage over the winter. Still inside the ticks, they transform into vermicular (worm-shaped) sporozoites through binary fission. The tick releases the sporozoites, which travel to the new host, when the tick takes another meal.

    Transmission

    • The life cycle of babesia requires two hosts: the tick to produce the sporozoites and the vertebrate host used for breeding. Anywhere that certain hosts are parasitized by ticks, the infection cycle occurs. Since transmission takes place directly through ticks, there is little to no chance of host-to-host transfer. In the northeastern United States, the parasitic cycle is mainly kept between black-legged ticks and white-footed mice.

    Geographic Distribution

    • The parasites are spread worldwide, but due to the similarity of malaria and babesia, it is difficult to measure prevalence in malaria-ridden countries. In Europe, most reported cases of the disease babesiosis occur in patients who had their spleen removed. In the United States, the most common reported strain is called babesia microti, regardless of the patients' having had their spleen removed. In Washington and California, the babesia duncani strain has been isolated in patients.  The MO-1 strain has been isolated in patients from Missouri.

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