Most of the summer diseases a rancher worries about hit calves. This one runs the other way. Anaplasmosis goes after the older cattle in the herd — the four-, five-, six-year-old cows that have raised good calves and never given you trouble. A calf can carry the organism and shrug it off. A mature cow can’t, and by late summer she’s the one you find down in the willows or standing off by herself, too weak to keep up.
The bug is a blood parasite that attacks red blood cells. The animal’s own immune system clears out the infected cells, and in doing so it strips the blood down until there aren’t enough left to carry oxygen. That’s why the disease looks like straight anemia once it gets going. The trouble is that by the time you can see it, the cow has already lost most of her red cells, and pushing a sick anaplasmosis cow — running her to the corral, hauling her in — is often what kills her outright.
What moves it, and why June matters
Anaplasmosis doesn’t spread on its own. Something has to move infected blood from one animal to another, and summer is when that traffic picks up. Ticks carry it. So do horse flies and other big biting flies that take a blood meal, get interrupted, and finish on the next cow over. And people move it too — a needle used on more than one animal, a dehorner or a tattoo pliers or a castrating knife that isn’t cleaned between head, all of it can carry a drop of blood far enough to matter.
That’s why the disease tends to show up weeks after the insects come out. The cow gets infected in June, the parasite builds through July, and she goes down in August or early September when everything else looks fine. If you’ve got carrier animals in the herd — cattle that survived a past infection and never fully cleared it — they’re the reservoir the flies keep drawing from all season.
What it looks like in the pasture
Early on there’s nothing to see. As the anemia sets in, the cow drops back from the bunch, goes off feed, and quits keeping up on the walk to water. Look at the membranes around her eyes and inside her mouth — instead of pink they go pale, then almost yellow as things get worse. She may breathe hard from the lack of oxygen in her blood. Some cows get aggressive or wild right before they go down, which catches people off guard because it doesn’t fit a sick animal. That’s the brain running short on oxygen.
Abortion is common in bred cows that get sick and pull through. And here’s the part that costs people: the stress of handling. A cow that’s severely anemic has almost no reserve. Gathering her hard, hot-shotting her up the alley, hauling her in a trailer on a warm day — any of it can be the last straw. If you think a cow has anaplasmosis, move her slow, in the cool of the morning, or better yet get a vet to look at her where she stands.
What you can actually do
Talk to your vet before you assume it’s in your herd, because a lot of things make a cow go off in August. A blood test will tell you whether you’re dealing with anaplasmosis and whether you’ve got carrier animals. Treatment for a sick cow is a tetracycline antibiotic, and it works better the earlier you catch her — which is another argument for actually riding through the older cows in late summer instead of counting heads from the truck.
Prevention comes down to cutting off the ways the blood moves:
- Change needles often when you’re working cattle, and don’t run one needle through the whole herd to save a few dollars. Same thinking on dehorners, knives, and tattoo pliers — clean them between animals.
- Stay after flies and ticks with whatever fits your operation, since the same fly control that helps with horn flies and pinkeye cuts down on this too.
- Know your carriers. If you buy cows or bring in outside cattle, understand you may be bringing the organism with them.
In parts of the country where the disease is a year-in, year-out problem, producers feed a medicated mineral through the vector season on a vet’s guidance to hold infections down. Whether that pencils out here depends on how much pressure you’ve got, and it’s a conversation worth having with your vet rather than a blanket recommendation.
The main thing is to know the pattern. If you lose a mature cow in the heat of summer and she looked pale and weak before she went, don’t just write it off. Get an answer, because anaplasmosis rarely takes just one.
