Anaplasmosis is a tick-borne disease affecting ruminants, dogs, and horses, and is caused by Anaplasma bacteria. Anaplasmosis is an infectious but not contagious disease. Anaplasmosis can be transmitted through mechanical and biological vector processes. Anaplasmosis can also be referred to as "yellow bag" or "yellow fever" because the infected animal can develop a jaundiced look. Other signs of infection include weight loss, diarrhea, paleness of the skin, aggressive behavior, and high fever.Many different tick species can carry the bacteria that cause anaplasmosis. The two major bacterial pathogens are Anaplasma marginale and Anaplasma phagocytophilum. These microorganisms  are Gram-negative, and infect red blood cells. Once the host is infected with anaplasmosis, the immune system will try to fight off and kill the infected red blood cells, but will also kill healthy red blood cells. The Anaplasma sparouinense species is responsible for a rare zoonosis, the Sparouine anaplasmosis, detected only in French Guiana, South America. This disease was described from a clandestine gold miner working deep in rainforest. Infection of his red blood cells led to a severe deterioration of his health and required his hospitalization. Molecular typing showed that Anaplasma sparouinense is distinct to all known species and more genetically related to recently described Anaplasma species causing infections in rainforest wild fauna of Brazil.While there are no current live or inactivated vaccines effective for all strains of A. marginale approved by the USDA for anaplasmosis, there are other means of prevention. Tick and fly control for herds of ruminants can be effective but also labor intensive.
Anaplasma marginale is found worldwide and is transmitted by Rhipicephalus ticks. Anaplasma phagocytophilum is also found worldwide, mainly transmitted by Ixodes ticks. Other species that cause anaplasmosis in specific species include:

Cattle:
Anaplasma centrale - found mainly in South America, Africa and the Middle East
Sheep and goats:
Anaplasma ovis - found worldwide. There is a prevalence of 82.9% in sheep, and 74.9% in goats. This species is the most prevalent for causing anaplasmosis in sheep and goats, although Anaplasma phagocytophilium can also cause the disease. Anaplasma phagocytophilium has a prevalence of 11.9% in sheep, and 15.2% in goats. Morphology
There are many strains of Anaplasma marginale, all with differing morphology, antigenic properties, protein sequence, and ability to be transmitted by ticks. Major surface proteins (MSP) have been found to play a major role in the infection by Anaplasma marginale. Out of the six MSP found on this species, three of the major surface proteins do not seem to differ between all strains, those including MSP1a, MSP4, and MSP5. The msp1a gene, which codes for MSP1a, is used as a marker for the identification of Anaplasma marginale because it has shown to be conserved in the multiplication of rickettsia in cattle and ticks and has been shown to be involved in adhesion to bovine erythrocytes and tick cells.Anaplasma phagocytophilum is a gram-negative bacterium that does not have lipopolysaccharides or peptidoglycan. The outer membrane does not have a capsule, and is coarse with irregular periplasmic spaces.