Becky Mills
Contributing Editor

Anaplasmosis is one of those diseases that will keep you awake at night. For starters, it is aggravating to diagnose. Sure, a simple blood smear will identify the responsible organism, Anaplasma marginale, unless you live in Florida where anaplasmosis insists on being special and has its own strain. So, what's the problem? Isaac Jumper, Mississippi State University (MSU) veterinarian, said, "When we see cases of anaplasmosis, it's typically in the fall. If you don't find the carcass quickly, there's not going to be a whole lot we can do from a necropsy standpoint. So, we likely underestimate the impact of anaplasmosis."

He added, "Although this disease was historically found around the Gulf Coast regions, it is an emerging disease in other places in the United States. We're moving cattle to places we've never moved them before."

LEARNING ABOUT THE DISEASE

First, though, a little Anaplasmosis 101. The Dermacentor tick, commonly found in the Southeast, is usually the culprit. When it feeds on an infected cow, the bacteria infect the tick where it replicates. When the tick bites another cow, it infects the cow.

"Ticks do not discriminate," added Jumper. "They feed on other mammals, particularly white-tailed deer. We can have a tick that hops on a deer in one part of the state and ends up in a cow herd in another place because ticks move around on the host they feed on. Ticks can also be a reliable way of moving the organism around in different herds."

Once a cow is infected, Jumper said the incubation period may range from seven to 60 days. You won't see clinical signs until this incubation period is up. However, he said, "That's very variable, and it really depends on how much of the organism the cow comes in contact with initially. If it's a small amount, it takes longer for the animal to develop clinical signs. If it's a larger amount, it can happen more quickly because clinical signs are derived from the amount of red blood cell destruction that happens in a short period."

Ticks aren't the only villains. Once a cow has anaplasmosis, biting flies can spread it, not because it replicates in their bodies but by carrying a tiny drop of blood from an infected cow, then biting another cow.

Well-meaning humans are also guilty. Using the same needles, ear tag applicators, or castration knives can spread the disease.

There are symptoms but they vary from vague to too late. Anaplasma marginale attacks red blood cells and causes anemia. Jumper said cows can act lethargic, lose weight and the lack of oxygen to their brain can cause them to be aggressive, all symptoms anaplasmosis shares with other diseases. "We can see abortions. The unique thing about anaplasmosis is it's not actually killing the fetus, it's the lack of oxygen carrying capacity."

Shorterville, Alabama, bovine veterinarian Perry Mobley said abortions are usually the first thing he sees with anaplasmosis; however, he added, "The other thing is just dead cattle."

Jumper agreed. If the carcass is found before it deteriorates too badly, he also said there are signs of jaundice. "That yellowing of the skin and mucus membranes is a result of the breakdown of those red blood cells. In black-hided animals, you'll see it around the prepuce in bulls or the vulva of cows."

If the body is in too bad of shape to do a necropsy, he said not to automatically assume it is anaplasmosis. He said producers need to work with their veterinarian since anaplasmosis is not the only disease that can cause sudden death in cattle.

For example, Jumper did a necropsy on a cow and she tested positive for anaplasmosis. "The producer insisted anaplasmosis was killing his cows. I said it is not anaplasmosis that's killing your cows. She has a body condition score (BCS) of 3.0 in January and she starved to death," he added.

"Often, any mysterious disease that happens between March and October where we just find a dead cow is blamed on anaplasmosis. In cases of anaplasmosis, a dead cow may be all we find if we don't catch her in that 12- to 14-hour window when she's experiencing clinical signs," Jumper said.

ANAPLASMOSIS IS DIFFERENT THAN OTHER DISEASES

Another perplexing trait of anaplasmosis is it typically hits mature cows. Jumper said, "This is unique. If calves become infected early in life, they typically do not experience clinical disease but are likely to be carriers for the rest of their life."

The MSU vet said, "In some cases, it might actually be advantageous if transmission is happening within a herd early in life, rather than adult cows becoming infected where they're more likely to experience clinical signs."

If a mature cow is carrying the organism, Jumper said she may develop clinical disease if she experiences some other disease or stressful event. "In healthy carrier animals, the immune response naturally controls the infection and the bacteria isn't able to replicate enough to cross the threshold of creating clinical signs again." However, he said, "If the cow is in poor body condition, or we've got circulating IBR or BVD virus in the herd or a severe parasite infestation, this can be a tipping point and you can have reoccurrences of clinical disease in some of these cows."

If you do catch a cow in that short time when she is showing clinical symptoms, you can try to treat her. Mobley said, "We use oxytetracycline on them, I.V. or Sub Q, just get it done." He warned, though, "Once they get down, you ain't hitting on much. They are so anemic, they just run out of gas."

For active infection, chlortetracycline may be used for control but requires a prescription from the herd veterinarian.

DISEASE PREVENTION IS IMPORTANT

Obviously, controlling biting flies and ticks with labeled fly control insecticides is an option, but good luck with that. You've probably noticed your go-to insecticides are getting more insect-resistant year by year. Mobley said, "Try other products, just like we do in the row crop business. When we get something that's resistant, we gotta come at it at a different angle. It may be an organophosphate. Next time, it may be a pyrethroid. It's sort of like a fella asked me, what's the best fly tag to use? I said if you wait 'til the end of the year, about December, I'll tell you, because you just don't know."

A cold, dry climate isn't necessarily in your favor, either. "The worst mosquitoes I have ever seen were at 6,000 feet in the high desert of New Mexico," said Mobley.

Time of year isn't a black or white deal, either. Jumper said, "Although we say most cases occur in the fall, it can really be any time of the year because in the Southeast, we see ticks and flies almost year-round."

Don't forget basic biosecurity, either. If your herd is anaplasmosis-free, quarantine any new arrivals until you can get them tested.

If your herd does have a problem with anaplasmosis, Jumper said there is a conditional vaccine through University Products, Baton Rouge, Louisiana. "Producers should visit with their veterinarian about the vaccine because it may be helpful in their herd."

Once again, he emphasized, "If you're experiencing a problem with bovine anaplasmosis, it is critical that you work with your veterinarian." He said this will confirm that bovine anaplasmosis is the cause of the illness and he or she can help you develop a plan to treat affected animals and prevent a reoccurrence.

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