Anaplasmosis is a disease caused by a bacterium (Anaplasma phagocytophilum). It is transmitted to humans by the bite of a tick (blacklegged or western blacklegged) About Anaplasmosis | Anaplasmosis | CDC. The blacklegged tick is found throughout the eastern half of the United States (from Minnesota down to Texas and every state east). The western blacklegged tick is found only in the western parts of Washington and Oregon, throughout California and in small sections of Nevada, Arizona and Utah. There have been rare instances of anaplasmosis occurring from a blood transfusion. First identified in the 1990s it became a notifiable disease to the Center for Disease Control in 1999 Epidemiology and Statistics | Anaplasmosis | CDC. Symptoms are like the flu, if not treated or illness occurs in immunocompromised or older individuals a severe case of anaplasmosis can occur. Severe symptoms are bleeding problems, difficulty breathing, organ failure and possibly death. Symptoms occur within 5-14 days after being bitten from an infected tick. Diagnosis is made by clinical history, tick bite history, blood test and molecular biology. Treatment is with antibiotics; recovery can occur if treated early. Prevention is staying away from tick infested areas and treating your animals with preventative measures.    

Anaplasmosis in animals is mainly a problem in cattle, although it has been detected in goats, sheep and horses Anaplasmosis in Ruminants - Circulatory System - Merck Veterinary Manual. It has been found in all 48 contiguous states in cattle mainly because of the interstate movement. Anaplasma marginale is the main cause of anaplasmosis in cattle. In young animals under a year old there are no signs of illness, compared to 1–2-year-old the animal is moderately ill. An adult over 2 years can become severely ill followed by death. Anaplasma is intracellular, found in the red blood cells and can cause anemia once the immune system starts attacking the red blood cells trying to destroy the parasite. Once the animal is exposed it can take up to 3-6 weeks before it is detected in the red blood cells. The number of red blood cells affected determine the severity of the illness.  Other symptoms are fever, anorexia, milk production will fall, some loose coordination, mucous membranes are pale, and abortion can occur. Cattle can become chronic carriers, which allows immunity from further infection, but relapsing can occur if the animal is stressed or becomes ill from another disease. This allows the disease to perpetuate in the herd and be spread to additional animals. Diagnosis is through blood smears and tests, molecular biology. Treatment is with antibiotics.

In Kentucky anaplasmosis is diagnosed in cattle during the late summer and fall, which means the time of infection occurred in early summer because of the long period time between exposure and invasion of the red blood cells Strategic Management of Anaplasmosis in Kentucky | Animal & Food Sciences. Between 2020-2025, there were 531 positive cases of anaplasmosis in cattle in the state Bovine Maps | University of Kentucky Veterinary Diagnostic Laboratory. 

Map of cattle anaplasmosis cases in Kentucky (courtesy of University of Kentucky Veterinary Diagnostic Laboratory)