Haemosporida

Haemosporida is an order of parasitic alveolate eukaryotes. These organisms are obligate intracellular parasites that infect blood cells of vertebrates. The life cycle of Haemosporida typically involves two hosts: a vertebrate host and an arthropod vector. In the vertebrate host, the parasite undergoes asexual reproduction, infecting red blood cells, and sometimes white blood cells or other tissues. In the arthropod vector, usually a mosquito or midge, sexual reproduction occurs.

The most well-known genera within Haemosporida are Plasmodium, Babesia, and Theileria. Plasmodium species are responsible for malaria, a significant human disease transmitted by mosquitoes. Babesia species cause babesiosis, a tick-borne disease that can affect both animals and humans. Theileria species are also tick-borne parasites that infect livestock, causing various diseases.

The transmission of Haemosporida occurs when an infected arthropod takes a blood meal from a vertebrate host. During this feeding process, the parasite, often in the form of sporozoites, is injected into the vertebrate's bloodstream. The parasite then migrates to its target cells, initiating the asexual phase of its life cycle. When an uninfected arthropod feeds on an infected vertebrate, it ingests gametocytes, which are the sexual stages of the parasite. These gametocytes mature and undergo fertilization within the arthropod's gut, leading to the development of infective sporozoites that migrate to the arthropod's salivary glands, ready to be transmitted to another vertebrate host. The study of Haemosporida is crucial for understanding and controlling vector-borne diseases.