Balantidium coli

Balantidium coli is a parasitic species of ciliate alveolates that causes the disease balantidiasis. It is the only member of the ciliate phylum known to be pathogenic to humans, although the main reservoir for this species are mainly domestic and wild pigs. In addition, B coli is known to infect multiple species of mammal including cattle, camels, sheep, buffalo, and rodents, as well as some birds and marine mammals in rare cases. B. coli has a world wide distribution, but tends to be spread more in humid and moist environments. Infections in humans are commonly seen in tropical and subtropical countries in central and south America and Asia, although prevalence between each site can vary widely.

Balantidium coli was first describes in the 1857 as Paramecium coli until being transferred to the genus Balantidium in 1863. In 2013 after genetic analysis comparing B. coli with other species in the genus, isolating B. coli into its own genus of Neobalantidium was proposed, although it has been used interchangeably with the genus proposed in 1931 Balantioides.