You go out to move a bunch in late July and one old cow is standing off by herself, breathing hard, gaunt through the flank. When you push her she gets snorty and mean, wheels around instead of trailing off with the others. Pull her lip up and the gum is pale, maybe a little yellow. That combination — an older cow, run down, short of air, and cranky about being handled — should put anaplasmosis near the top of your list.
Anaplasmosis is a blood parasite that gets into a cow’s red blood cells and destroys them. The cow ends up anemic, starved for oxygen, and that’s what drives most of what you see. It’s not new, and it’s not rare in Montana, but it tends to show up on grass in the back half of summer when the fly and tick population is up. A lot of producers who’ve never had a problem run cattle for years and then buy in one carrier or turn out onto a pasture where the bug is established, and suddenly they’re dealing with it.
Why it’s the old cows that die
Calves and yearlings get infected all the time and shrug it off — they carry the parasite without ever looking sick. The trouble is that susceptibility climbs with age. Cows past three years old show real disease, and cows past five or six are the ones that die. So the animals you can least afford to lose, your proven older cows, are exactly the ones this thing kills.
The signs build slowly because the anemia builds slowly. A cow lags behind, drops off in condition, quits eating well, and gets weak. As she loses red cells the membranes go pale, then jaundiced. Bred cows can abort. And here’s the part that catches people: an anemic cow is already running on the ragged edge for oxygen. If you gather hard, run her up a hill, or crowd her into a chute, the exertion can flat kill her. That mean, aggressive behavior you sometimes see is a starved brain, not a bad attitude. When you suspect anaplasmosis, handle slow or don’t handle at all until you’ve talked to your vet.
How it gets from one cow to the next
Two roads. The natural one is biting insects and ticks — horse flies and other biters, and the ticks that come out on the brushy draws and timbered country. They pick up infected blood off a carrier and carry it to the next cow. The other road is you. Any tool that moves blood from one animal to another spreads it: a needle reused down the whole chute line, dehorners, castrating knives, tattoo pliers, even a nose lead. One dirty needle through a carrier and then through your best cows will do more damage than a summer’s worth of flies.
That last part is worth chewing on, because it’s the road you actually control. Change needles often when you’re working cattle. Disinfect anything that cuts or draws blood between animals. It’s a small hassle at branding or preconditioning that pays off in a big way.
Once a cow survives the infection she becomes a lifelong carrier. She looks fine, breeds, raises calves, and stays a reservoir the flies can tap into forever. That’s why a purchased cow or bull can walk the disease onto a clean place. If you’re buying breeding stock, it’s worth a conversation with your vet about testing, especially bulls that’ll be in the pasture spreading their blood around all summer through fights and flies.
Keeping it out and keeping it down
There’s a treatment — injectable oxytetracycline will pull a sick cow through if you catch her before the anemia gets too deep, and your vet is the one to walk you through dose and handling. On outfits that have a known problem, feeding chlortetracycline through a mineral or feed during vector season is the common control tool, but that now requires a veterinary feed directive, so it’s a plan you build with your vet ahead of the fly season, not something you grab off the shelf in August.
The everyday stuff matters too. The fly control you’re already running for horn flies and face flies cuts down on the biters that move anaplasmosis, so a good fly program does double duty. Clean needles and clean tools at every working. And pay attention in the second half of summer — the sooner you notice the cow hanging back, the better her odds, and the less likely you are to lose her to the gather instead of the disease.
