The disease that takes your best mature cow in late summer usually doesn’t announce itself. She grazes with the bunch, then one morning she’s off by herself, breathing hard on a short walk, hanging back when the rest string out to water. If you get her in and pull her eyelid down, the membrane that ought to be pink is pale, sometimes yellow. That’s anaplasmosis, and by the time you see it the damage is well along.
It’s a blood parasite that gets into red cells and destroys them. The animal turns anemic. Where a young calf can carry the organism and shake it off, an older cow can’t rebuild blood fast enough, and the ones over about three years old are the ones that die from it. That’s the cruel part. Anaplasmosis kills your proven cows and mature bulls, the animals you’ve spent years developing, and it tends to hit them in July and August when the country is dry and the flies are worst.
How it moves through a herd
Anaplasmosis travels in blood, so anything that carries a little blood from one animal to another can spread it. Biting flies and ticks do plenty of the work on summer range. So do you, if you’re not careful. A single needle run through a dozen head at branding or a preconditioning day will move it right down the line. Same with a dehorner, a tattoo pliers, an ear tagger, or a castrating knife that isn’t cleaned between animals. A carrier cow can look perfectly healthy and still be a reservoir for years, seeding the herd every time a fly feeds on her and then lands on the next cow.
That’s why the trouble often shows up weeks after you handled cattle, not during. The organism takes a month or more to build up before the animal gets sick. You gathered and worked pairs in the spring, everything looked fine, and now it’s high summer and a couple of older cows are dragging.
What it looks like in the pasture
Watch for a mature animal that separates from the bunch and tires easily. Anemia makes them short of breath and weak, so a cow that’s normally sound may act winded after walking to water. The eye and gum membranes go from pale pink to white, and often a yellow tinge shows up as the breakdown of red cells overloads the system. Some cows go strange and aggressive right before they go down, which is the body starving the brain of oxygen. Others just get weaker until they can’t rise.
Here’s the mistake that costs cattle: chasing and roping a sick one. An anaplasmosis cow has almost no reserve. Run her hard to doctor her and she can drop dead from the exertion alone. If you suspect it, move her slow, or better, treat where she stands. A blood test through your vet confirms it and tells you whether you’re dealing with one sick animal or a herd that’s carrying the organism.
Treatment is oxytetracycline, and it works better the earlier you catch it. A vet can walk you through the dose and whether a longer course makes sense. But a cow that’s already down and severely anemic is a long shot no matter what you put in her, so the value is in catching the early ones and in keeping the disease from spreading in the first place.
Cutting down the spread
You can’t sterilize the flies, but you can quit being a vector yourself. Change needles often when you’re processing cattle, and don’t run one needle through a whole group to save time. Clean your dehorners, knives, tattoo and tagging tools between animals, or at least disinfect them when you move down the chute. Fly control that knocks back biting flies helps on the insect side, along with everything else it does for your herd.
Where anaplasmosis is a known problem, a lot of outfits feed a medicated mineral with chlortetracycline through the fly season to hold it in check. That takes a veterinary feed directive from your vet now, so it’s not something you decide on a Sunday when a cow gets sick. If you’ve had unexplained summer death loss in older cows, or you’re buying cattle out of country where the disease is common, it’s worth a conversation before turnout instead of after.
The frustrating truth is that a healthy carrier cow standing in your herd right now may be the source, and you’ll never pick her out by looking. That’s why the cheap habits matter, the clean needle and the wiped-off knife. They cost you a few minutes at branding and save you the cow you can’t replace.
