<unk>  is a genus of bacteria of the spirochete phylum. Several species cause Lyme disease, also called Lyme<unk> sis, a zoonotic, vector-borne disease transmitted by ticks. Other species of<unk>  cause relapsing fever, which are transmitted by ticks or lice, depending on the species of bacteria. The genus is named after French biologist Amédée Borrel (1867–1936), who first documented the distinction between a species of<unk> , B. anserina, and the other known type of spirochete at the time, Treponema pallidum. This bacterium must be viewed using dark-field microscopy, which make the cells appear white against a dark background.<unk>  species are grown in Barbour-Stoenner-Kelly medium. Of 52 known species of<unk> , 20 are members of the Lyme disease group (with an additional 3 proposed), 29 belong to the relapsing fever group, and two are members of a genetically distinct third group typically found in reptiles. A proposal has been made to split the Lyme disease group based on genetic diversity and move them to their own genus, Borelliella, but this change is not widely accepted. This bacterium uses hard and soft ticks and lice as vectors. Testing for the presence of the bacteria in a human includes two-tiered serological testing, including immunoassays and immunoblotting.
Borrelia
Plasmodium
Leishmania
Treponema
Cryptosporidium
Chlamydia 
Chlamydia
Sepik virus