subtropical countries. Anaplasma phagocytophilum (formerly Ehrlichia phagocytophila) is a bacterium of deer that spreads to sheep where it causes tick-borne fever in Europe, resulting in abortion by ewes and temporary sterility of rams. This bacterium invades and proliferates in neutrophil cells of the blood. This depletes these antibacterial cells and renders the host susceptible to opportunistic infections by Staphylococcus aureus bacteria which invade joints and cause the crippling disease of sheep called tick pyaemia. Anaplasma marginale infects marginal areas of red blood cells of cattle and causes anaplasmosis wherever boophilid ticks occur as transmitters. Anaplasma centrale tends to infect the central region of red blood cells, and is sufficiently closely related to An. marginale to have been used from long ago as a live vaccine to protect cattle against the more virulent An. marginale. Sheep and goats suffer disease from infection with Anaplasma ovis which is transmitted similarly to the anaplasmas described above. Ehrlichia ruminantium (formerly Cowdria ruminantium) is transmitted mainly by Amblyomma hebraeum and Am. variegatum in Africa, causing the severe disease heartwater in cattle, sheep, and goats. This disease is named after the prominent sign of pericardial edema. The bacteria infect the brain, causing prostration. Heartwater also occurs on the Caribbean islands, having spread there on shipments of cattle from Africa about 150 years ago, before anything was known of tick transmitted microbes. Protozoal diseases Babesia bovis protozoa are transmitted by R. microplus and cause babesiosis or redwater fever in cattle throughout the tropics and subtropics wherever this boophilid species occurs. The less pathogenic Ba. bigemina is transmitted by R. microplus and R. decoloratorus. Development of Babesia in the tick is complex and includes sexual reproduction. These Babesia are transmitted from adult female boophilid ticks to the next generation, as larvae, by infection of the eggs. This is known as transovarian transmission; it provides the only opportunity for transmission through one-host ticks. Other species of Babesia are transmitted by three-host ticks in ways similar to Theileria protozoa, as described below. In cattle, infection of the red blood cells may grow rapidly to create a potentially fatal inflammatory crisis of the blood. The name redwater (coloured urine) derives from the hemoglobinuria caused by the destruction of red blood cells infected with the merozoite stage of Babesia; anemia results from the same destruction. Horses suffer babesiosis or biliary fever when infected by Ba. equi or B. caballi. This occurs in