Anaplasmosis, sometimes called gallsickness, is a disease of domestic and wild animals, caused by the rickettsial parasite Anaplasma marginale, which invades and destroys the erythrocytes, causing anaemia and severe digestive disturbance. There can also be a reduction in milk productivity. It is transmitted by a number of species; mechanical transmission by biting flies and unsterilized syringe needles also occurs. Some wild ungulates carry infection without showing symptoms.
Anaplasmosis is widely distributed through tropical Africa, Asia, Australia and America.