Anaplasmos is an acute (rapid onset and short but severe), fever producing disease of cattle, usually transmitted by blue ticks and caused by parasite which multiplies in red blood cells, causing a severe anaemia. Severe Anaplasmosis is caused by Anaplasma marginale. This parasite occurs at the edge of the red cells. A mild, usually inapparent form is caused by Anaplasma centrale. This parasite occurs at the centre of the red blood cell.

The incubation period of the disease is about 2 - 12 weeks and is directly related to the infective dose. The disease occurs throughout the tropical and subtropical regions of the world

Infections in the sucking young usually does not happen. Once infected, animals remain carriers for life. In areas where cattle first become infected with Anaplasma marginale early in life, losses due to anaplasmosis are minimal. In animals less than 1 year old Anaplasmosis is usually subclinical, that is, there are no symptoms in yearlings and 2 year olds it is moderately severe, and in older cattle it is severe and often fatal.

Exposure of calves to infected ticks gives them an often life-long resistance. Paradoxically efficient tick control at this stage of their life will later expose cattle to possible life-threatening anaplasmosis. These facts must be kept in in mind at all times. Zebu cattle, with their relative resistance to heavy tick infestations, are less likely to be infected, but they are just as susceptible as European breeds.
Carrier animals serve as reservoirs for further transmissions.
Serious losses can occur when mature cattle with no previous exposure are moved into areas where the disease is prevalent or when transmission rates are insufficient to ensure that all cattle are infected before reaching the more susceptible adult age. This latter situation can occur when a previously effective acaricide becomes ineffective especially when it has previously been effective from calfhood into adulthood.

Onset of illness is characterised by the following:

• Rising fever of up to 41 C ( 106 F) ,
• Drop in milk production,
• Decreased appette.
• Saverely affected animals lose condition rapidly and very saverely affected animals may die within a few hours of the onset of symptons.
• Saverely affected animals are depressed, lose their co-ordination and become breathless, and lag behind the rest of the herd if exerted. If forced to walk some of these animals may even lie down. These symptoms are directly related to the degree of anaemia caused by the destruction of red blood cells.
• Examination of the eyes and vulva will reveal a change from a healthy pink to a pallid white to yellow or even light orange colour. This indicates the onset of jaundice due to liver damage. The teats of a milking animal appear pale or white in colour.
• There is a rapid bounding heart rate. This is easily heard by pressing one's ear against the animal's pelvis. This loud beat, heard several feet from the heart itself, is almost disgnostioc for Anaplasmosis. It cannot be heard in a normal animal.
• The urine may be yellow or even brown, but, unlike Babesiosis (Redwater) contains no red blood cells.
• Constipation is common.
• Pregnant animals often abort.
• Some animals are hyperexitable and aggressive, charging and attacking people.
• In the severe form of the disease, there may be death if immediate treatment is not given.
• In dead animals, blood is thin and watery and the flesh is pale yellow. The liver is yellowish orange. The gall bladder is large and full of brownish greenish fluid and the kidney is large and soft. The spleen is enlarged and mushy.