Pet Talk —
Fall’s arrival means it’s time for cattlemen to watch their herds for signs of anaplasmosis. This disease can be devastating if not treated properly or in a timely manner.
Anaplasma marginale is a parasitic organism transmitted through blood transfer by biting insects and ticks, or by surgical instruments such as needles. The organism attaches to red blood cells, which the body then removes, causing cattle to become anemic, explained Dr. Meredyth Jones, assistant professor at the Texas A&M College of Veterinary Medicine and Biomedical Sciences’ Large Animal Hospital.
Anaplasmosis appears most often in the fall because symptoms surface 21 to 45 days after infection — typically after the busy biting fly season of late summer. Cattlemen in Southern states need to be particularly cautious because the disease appears most frequently south of Kansas.
“Many times cattle can be infected and show no signs of illness,” Jones said. “But during the fall months, if we are called on to examine a sickly, weak cow, anaplasmosis is high on our list of culprits.”
Cattle in the acute phase of infection may appear weak, “down” and generically sick due to anemia. Affected cattle may also exhibit white or yellow mucous membranes — such as eyes, muzzles, udders and vulvas. These membranes will appear white due to a lack of red blood cells, or yellow because of the pigments released as red blood cells are broken down and removed from the body.
Some cattle may even exhibit signs of aggressiveness, a behavior caused by lack of oxygen to the brain.
Anaplasmosis may appear in a chronic form, caused by a moderate level of anemia. Affected cattle lose weight over time, which can cause abortions in pregnant cows. The blood of infected cows in both phases will be thin in consistency, almost watery, when examined.
“For a clinical diagnosis, veterinarians will commonly test a cow’s blood for anaplasmosis with a blood smear,” Jones said. “We can actually see the organism attached to the margin of red blood cells with a microscope.”
In the acute phase, anaplasmosis can be fatal if not treated properly. Ill cattle must be treated with great care, said Jones, because the stress of handling cattle can be fatal if the disease is advanced.
“If you suspect a cow of being infected, don’t chase her with horses or dogs if you can help it. You really need to handle them delicately to reduce their stress as much as possible,” Jones said.
The most common treatment is the use of tetracycline antibiotics. Improvement in cattle’s symptoms can be seen within a few days, but it takes between two to four weeks to see a significant recovery of red blood cell numbers.
As with most diseases, prevention is ideal. Jones recommends fly tags, rubs and pour-on insect repellents to ward off biting insects and ticks. She also suggests changing needles between each cow when vaccinating or administering medicines. Another option is to add low levels of chlortetracycline to the feed to kill the organism before it replicates and attaches to red blood cells.
Unlike many diseases, which attack young and elderly populations, anaplasmosis mostly affects middle-aged cattle. In fact, most deadly cases occur in cattle between six and eight years of age. Younger cattle are better able to regenerate red blood cells and recover, often developing immunity.
Jones says cattlemen should pay particular attention to their adult cows and bulls as the season progresses, watching for symptoms characteristic of anaplasmosis.off the shelves.
PET TALK is a service of the College of Veterinary Medicine & Biomedical Sciences, Texas A&M University.