This year, confirmed cases of anaplasmosis throughout Kansas and beyond are at some of the highest numbers veterinarians have ever seen. With the high incidence of cases, it is important for cattle producers to be aware of what causes the disease and how it can rapidly spread through herds.
“I’ve been in the diagnostic lab for five years in the (K-State) College of Veterinary Medicine, and the number of positive reported herds in Kansas this summer with anaplasmosis is something we’ve never seen before,” said Gregg Hanzlicek, veterinarian and director of production animal field investigations for the Kansas State Veterinary Diagnostic Laboratory.
Anaplasmosis is a vector-borne disease that causes the destruction of red blood cells in cattle and other ruminants. The most common cause is a parasite called Anaplasma marginale. The organism enters the bloodstream and gets inside of red blood cells. The spleen then recognizes these red blood cells as a threat and attempts to purge them, which leads to the animal becoming anemic.
Signs of infection
Hanzlicek said many signs indicate an animal is infected with anaplasmosis, and producers should monitor their herds closely for these signs, which are all associated with anemia.
“They can be open-mouth breathing and staggering,” he said. “Sometimes they will get a yellow tinge to the whites of their eyes or the vulva.”
The disease can cause abortions in cows. Hanzlicek attributes at least four abortion cases last year to anaplasmosis.
“One of the most common things is these animals become extremely aggressive,” Hanzlicek said. “This is because their brain is starved for oxygen due to the anemia, and therefore, not enough oxygen is reaching the brain.”
He warned that while animals of all ages can become infected, the clinical signs will most likely only be exhibited by animals over the age of three years, with calves rarely showing clinical signs.
Causes of infection
Male dog ticks or wood ticks are the main carriers of anaplasmosis, Hanzlicek said.
“Male ticks are what we call intermittent feeders,” he said. “This means they’ll feed on an animal, and then they’ll drop off to find another animal to feed on. If the first animal is infected, the tick will consume the bacteria, which reproduces in the tick’s body. The tick falls off and finds another animal that may not be infected. The tick then transfers the bacteria through its saliva while feeding on the uninfected animal.”
Hanzlicek said in a recent Kansas Veterinary Diagnostic Lab study, researchers collected hundreds of ticks from around Kansas. More than 33 percent of all of the ticks collected tested positive for Anaplasma marginale.
However, ticks are not the only transmitters of the disease, he said. Anything that transfers blood between animals can be a source of infection, including stable flies, horse flies, deer flies and mosquitoes.
“Our activities when working cattle can also transmit the disease,” Hanzlicek said. “For herds that are already positive, one of the major ways this disease spreads from animal to animal is by not changing needles between animals.”
Some ways to mitigate the risk of infection through human activities is to change needles, and disinfect tattoo pliers and dehorning instruments between animals.
While most infected cattle will survive even if not treated, some will die from the disease.
“One good thing about anaplasmosis is that there are several good injectable oxytetracycline products out there that will reduce the clinical signs and save some animals,” Hanzlicek said. “I would recommend producers call their veterinarian to diagnose the disease and utilize their advice on what products work best to reduce the clinical signs.”
He stressed the importance of handling infected animals with extreme care and caution. Due to their anemic state, any added stress will sometimes cause older cattle to die from going to or through a chute.
In addition to injectable antibiotics, Hanzlicek said there are several chlortetracycline products labeled for treating an active Anaplasma infection that producers can feed.
“These products help in treatment of active infection in herds, and they can be effective in reducing clinical signs,” he said. “This is a feed-grade antibiotic, which means whatever it says on the label has to be followed exactly by the producer.”
Producers should consult their veterinarian about using feed-grade antibiotics, he added. This is especially important because over the next year with the phasing out of non-medically important antibiotics, producers will have to receive a veterinary feed directive (VFD) from their veterinarian to use chlortetracycline to protect against anaplasmosis.
Other factors to consider
“Regardless if an animal is treated, if an infected animal survives, it will be a carrier for the rest of its life,” Hanzlicek said. “Therefore, it is going to be a source of infection for the rest of the herd.”
If an animal is a carrier and is re-infected, it will not show the clinical signs the second time, he said.
“That is really the only good thing about the disease is a lifelong immunity to showing clinical signs,” Hanzlicek said. Some research suggests that up to 16 percent of the calves born to positive anaplasmosis cows will also be positive anaplasmosis carriers at birth.
Ensuring all new cattle in the herd are free of anaplasmosis by taking a blood test is crucial, he added. New arrivals should be quarantined until test results confirm that the disease is not present in the new animals.
“Late summer and early fall are typically the peak time of year for observing the clinical signs,” Hanzlicek said. “It is important to remember there are other things that may kill adult animals or cause these clinical signs. If a producer sees any of the signs mentioned, contact a local veterinarian to assist with the diagnosis.”