Anaplasmosis is a Rickettsial orgamism “Anaplasma marginale” that affects the red blood cells. Affected red blood cells are attacked and removed from circulation causing fever and severe anemia, which can lead to death.
Anaplasmosis is spread mechanically by carrying A. marginale- infected RBCs from diseased cattle to susceptible cattle by the bite of the common tick, horsefly, stable fly, mosquito or any instrument which can transmit blood. Applications of insecticides that reduce the biting insect population will substantially reduce the number of clinical anaplasmosis cases occurring in a herd, but cannot prevent it alone.
Outbreaks = No Controls (No antibiotic in feed/mineral) + Carriers +Susceptible Animals + Vectors (No fly/tick control).
Anaplasmosis can be divided into four stages: incubation, developmental, convalescent, and carrier. The incubation stage begins with the original infection with A. marginale and lasts until 1 percent of the animal’s red blood cells (RBCs) are infected. The average incubation stage ranges from 3 to 8 weeks. After gaining entry into a susceptible animal, the anaplasma parasite slowly reproduces in the animal’s blood during the incubation phase. During this period the animal is healthy and shows no signs of being sick. Finally, after the parasite has reproduced many times and established itself in the RBCs of the animal, the body attempts to destroy the parasite.
During the developmental stage, which normally lasts from 4 to 9 days, most of the characteristic signs of anaplasmosis appear. Clinical signs begin to be expressed about halfway through this phase. As the infected animal’s body destroys the parasite, RBCs are destroyed as well. When a substantial loss of RBCs has occurred, the animal will show signs of clinical anemia. The body temperature will commonly rise to 104 to 107 F , and a rapid decrease in milk production will occur in lactating cows.
Cattle producers first notice the anemic, anaplasmosis-infected animal when it becomes weak and lags behind the herd. It refuses to eat or drink water. The skin becomes pale around the eyes and on the muzzle, lips, and teats. Later, the animal may show constipation, excitement, rapid weight loss, and yellow tinged skin. The animal may fall or lie down and be unable to rise. Affected cattle either die or begin a recovery 1 to 4 days after the first signs of the disease. Unless infected cattle can be detected during the early developmental stage, they should not be treated. There are two primary reasons for this practice. First, if the animal is forced to move or becomes excited, it may die of lack of oxygen. Second, antibiotic treatments do little or nothing to affect the outcome of the disease when given during the late developmental or convalescent stage.
Cattle that survive the clinical disease lose weight, abort calves, and recover slowly over a 2- or 3-month period. This is known as the convalescent stage, which lasts until normal blood values return.
Cattle of all ages may become infected with anaplasmosis, but the severity of illness increases with age. Calves under 6 months of age seldom show enough signs to indicate that they are infected. Cattle 6 months to 3 years of age become increasingly ill, and more deaths occur with advancing age. After 3 years of age, 30 to 50 percent of cattle with clinical anaplasmosis die if untreated.
To help prevent an outbreak of anaplasmosis during the peak vector season you can feed Chlorotetracycline in the mineral or feed at 0.5 mg per pound per day from July to late October (120 days). Higher levels of CTC are needed during an outbreak! Multiple confirmed cases have been reported in Lincoln, Mitchell, Cloud and Jewell county.