Most of the summer cattle problems get plenty of talk around the sale barn — pinkeye, foot rot, flies thick enough to darken a black hide. Anaplasmosis doesn’t. It moves slower and quieter, and the first sign a lot of outfits get is a heavy cow found dead in the brush with no obvious cause. By then the disease has usually been working through the herd for weeks.
It’s worth understanding now, in mid-June, because the timing lines up. Anaplasmosis is spread by anything that moves blood from one animal to another — biting flies, ticks, and dirty needles or tattoo pliers used during working. All three of those are in full swing as the weather warms and you’re pushing pairs out to summer country.
What the disease actually does
Anaplasmosis is caused by a blood parasite that attacks red blood cells. The animal’s own immune system destroys the infected cells, and the result is severe anemia. That’s why the visible signs are about oxygen, not infection in the usual sense. A sick cow gets weak and falls behind the herd. Her membranes — gums, the inside of the eyelid — go pale, sometimes yellowish. She breathes hard after the smallest effort. Late in the game, animals can get aggressive or disoriented from lack of oxygen to the brain, which is a good way for a handler to get hurt trying to doctor her.
The part that catches people off guard is the age pattern. Calves rarely show much. Yearlings get sick but usually pull through. It’s the mature cows and bulls, three years and up, that die — and those are the most valuable animals in the herd. Lose a couple of solid older cows in a summer and you’ve paid for a lot of fly tags.
Animals that survive don’t clear the parasite. They become carriers, looking perfectly healthy while serving as a reservoir for the rest of the herd. That carrier status is the reason buying in outside cattle can light up a herd that never had a problem before.
Where Montana fits
This isn’t strictly a southern disease anymore. Cases turn up across a wide range of country, and movement of cattle has carried carriers into places that used to be considered clean. If you run cattle in tick habitat, along brushy bottoms and timbered draws, or you bring in bred cows, bulls, or replacements from out of state, you’ve got the pieces in place. Hot, dry summers don’t stop it; the fly and tick activity that drives transmission keeps right on going.
One thing to take seriously is your own equipment. A single needle reused across the chute during spring shots or a tattoo plier that isn’t cleaned between calves can transfer the parasite just as efficiently as a horse fly. Dehorning and castration tools count too. None of that costs anything to fix — change needles, disinfect tools — but it’s the kind of thing that gets skipped when you’re trying to get a hundred head worked before the heat sets in.
What you can actually do about it
There’s no quick fix once a cow is down hard, so the practical work is all prevention and early catching. A few things worth thinking through with your veterinarian:
- Know whether you have it. Blood testing can tell you if carriers are already in the herd. That changes how aggressive you need to be and whether new deaths are likely anaplasmosis or something else.
- Control the vectors. The same fly management you’d run for pinkeye and production losses — tags, pour-ons, rubs, feed-through products — cuts down transmission. It won’t eliminate it, but fewer biting flies means slower spread.
- Medicated mineral or feed. In herds with a known problem, feeding chlortetracycline through the mineral during vector season is a common approach to suppress the parasite. This is a labeled use that requires a veterinary feed directive, so it’s a conversation to have before you need it, not after.
- Clean instruments. Single-use needles and disinfected tools at branding and processing. Cheap insurance.
- Be careful buying in. Older cows and bulls from unknown sources can carry it in. Knowing the disease status of incoming cattle is worth asking about.
The reason anaplasmosis is worth your attention in June isn’t that it’s the biggest killer on the place. It’s that the losses fall on your best, oldest, most productive animals, and the management that prevents it overlaps almost entirely with work you’re already doing for flies. Spotting the pale-gummed cow before she’s down, and knowing why she’s that way, is most of the battle. If you’ve had unexplained losses in mature cattle in past summers, it’s worth a call to your vet about testing the herd before fly season hits its stride.
