Now considered an endemic area, southeast Kansas has seen its fair share of anaplasmosis cases in the past year, a fact made even more concerning by restrictions on chlortetracycline. During the Kansas State University Extension Beef and Pasture meeting in Fredonia, Kansas, K-State Vet Diagnostic Lab veterinarian Gregg Hanzlicek broke down the anaplasmosis information producers need.
“Once an animal becomes infected with anaplasma marginale, these organisms attack and begin the reproduce in the red blood cell,” Hanzlicek said. “It does two things — one, it changes the protein structure of the outside of the red blood cell plus it makes it so it’s not circular anymore.”
A red blood cell’s shape is not a problem for the animal until the blood cell encounters the spleen, Hanzlicek said.
“The problem is the spleen checks the cells as they pass through circulation and eliminates any abnormal cells,” Hanzlicek said. “It begins to take the infected red blood cells out of circulation, and then eventually we have an animal that becomes anemic.”
As a result of the anemia, animals exhibiting clinical signs of anaplasmosis will look pneumatic and breathe heavily. The membranes in the animal’s eyes or vulva, as well as its spleen, will be icterus, or turn a slimy yellow color.
“The reason they’re breathing heavily is their body is starved for oxygen,” Hanzlicek said. “Their body is trying to bring more oxygen into the lungs but the problem is not the lack of oxygen in the lungs, it’s the lack of red bloods cells to transport the oxygen to their tissues.”
Hanzlicek encouraged producers to test their animals with the two available tests for anaplasmosis to determine carriers within their herds and also to necropsy any adult animal they expect has died from anaplasmosis.
“We’ve had several cases over the last few years where the producer thought an animal died of anaplasmosis but it actually died from various other causes like too much rumensin in the cake they were feeding, salt toxicity or oil field chemical poisoning,” Hanzlicek said. “If you have adult animals dead in the pasture, consider calling your veterinarian to ask for advice on a necropsy.”
An anaplasmosis necropsy will reveal an icterus and enlarged spleen, Hanzlicek said. The spleen is a key indicator of an anaplasmosis death.
“The reason the spleen increases in size is because it is working very hard to clear out all of the red blood cells infected by bacteria,” Hanzlicek said. “The spleen is just like a muscle so as it works harder it just keeps getting bigger and bigger.”
“One of the major players, especially in eastern Kansas, is the tick,” Hanzlicek said. “For us it’s the American dog tick, where Oklahoma will have winter ticks and moose ticks as carriers as well.”
When the tick feeds on an animal, the bacteria reproduces inside the tick, making them biological amplifiers. A tick could be infected with just 10 organisms and fill with more than 10 billion to pass on, Hanzlicek said.
Male ticks are the primary culprits, as they move from animal to animal in search of food and mates. Whereas female ticks feed once and then fall of the produce their offspring and die.
Not all Kansas ticks are anaplasmosis carriers. The Lone Star tick, a small tick with a tiny white dot on its back, is not a carrier for anaplasmosis at all.
Hanzlicek said a K-State study collected 310 ticks from 21 locations in Kansas and 35 percent of those were positive for anaplasmosis.
While horn flies are not a likely carrier for anaplasmosis — they live on the same animal almost their entire lives — horse flies could definitely be contributing to the spread of anaplasmosis.
“In a 1940s study researchers tagged horse flies and recorded their flight distance, finding them three to eight miles away,” Hanzlicek said. “The anaplasmosis bacteria can live in their bill anywhere from three minutes to two hours and infect other animals.”
However, flies are not biologic amplifiers like ticks, so once the bacteria they carry dies, they are no longer carriers until they bite an infected animal again.
The primary spreader of anaplasmosis is cattle owners themselves, Hanzlicek said.
Tattoo pliers and needles are No. 1 spreader of anaplasmosis from animal to animal in positive herds.
A K-State study focused on 11 animals, infecting 2 percent of one of those animal’s red blood cells. They placed the infected animal in a chute and injected it, as well as the 10 negative animals with an automatic syringe as if giving vaccinations. After isolating the 10 animals, they were retested 60 days later, with six of the 10 positive for anaplasmosis.
“What this suggests is if you have a positive animal in the chute and you inject the animal behind it, there is a 60 percent probability that uninfected animal will be infected,” Hanzlicek said. “It does not take much blood at all to pass this organism from a positive animal to a negative animal.”
“The goal of a positive herd in an endemic area is to become endemically stable,” Hanzlicek said. “Endemically stable means you have a positive herd but you rarely, if ever, show clinical signs.”
The only way endemically stable is achievable is if the majority of the older animals in the herd were already positive and the only animals being infected are young animals who won’t show clinical signs. When older animals are newly infected with the disease, it takes their immune system up to seven days to respond to the bacteria and mount a defense, whereas younger animals’ immune systems react immediately.
Hanzlicek cautioned producers against trying to intentionally spread the bacteria to the younger members of the herd, as using unclean needles or tattoo pliers could transfer even worse diseases through the blood. In a positive herd in an endemic area, young animals will be exposed to the disease at an early age, with up to 19 percent receiving the bacteria in the mother’s womb before they are born.
For older animals infected with the bacteria, Hanzlicek suggested consulting a veterinarian on effective antibiotics to combat the clinical signs of the disease. However, he wanted producers to recognize that once infected with the bacteria, an animal with anaplasmosis would carry it for the rest of its life, even after ceasing to exhibit the clinical signs.
“There are some really effective antibiotics out there for the treatment,” Hanzlicek said. “If you have animals exhibiting the clinical signs of anaplasmosis, treating them will reduce those clinical signs and minimize death loss.”