October and November are when I get most of my phone calls about anaplasmosis. Cows are primarily exposed to ticks and biting flies throughout the summer. The incubation period is generally four-six weeks, and ticks can spike in activity in late summer. This results in cows either showing clinical signs or being found dead at this time of year.

Anaplasmosis is caused by the bacterium Anaplasma marginale, which destroys red blood cells. Transmission is mostly from ticks and biting flies, but we can also spread the disease with needles, castration knives, palpation sleeves, implant guns, tattoo and dehorning equipment.

We are seeing anaplasmosis move farther north, so areas of the U.S. that used to have little to no disease are seeing cases. This is a concern because when the disease is introduced into a naïve herd, death loss can be quite high.

Once an animal is infected, it is infected for life. Positive cows serve as carriers of the disease, and any of the previously mentioned transmission routes can move the disease from a carrier cow to a naïve cow. The naïve cow becomes infected and shows clinical signs or may die. The bacteria enter the cow’s red blood cells (RBCs), and they double every 24 hours. Even if a cow gets a tiny dose initially, she will develop full-blown disease. In cows exposed to a minuscule dose, the incubation period is much longer. We can see these cows showing signs 60-100 days after exposure.

The initial clinical signs show a cow that seems depressed, has labored breathing (they are severely deficient in RBCs carrying oxygen to the tissues), or has an abortion. As the disease progresses, the cow becomes very low on RBCs, and the skin and mucous membranes become yellow. Cows can become very aggressive (I had one try to get inside my vet truck one time) and have very firm feces. Be extremely careful around cows with suspected anaplasmosis. A previously tame cow can attack you. You also do not want to stress the cow because you can cause her to die due to lack of oxygen.

Clinical signs can be very similar to Theileria, which is also spread mostly by ticks and biting insects. Most veterinary diagnostic laboratories can test for both diseases.

Treatment of affected cows with the label dose of long-acting oxytetracycline can prevent further clinical signs and potentially death. It does not prevent the disease or clear the carrier state. Some older work indicated that multiple doses of LA oxytetracycline could clear the carrier state, but recent work shows that is not the case.

Young calves can be infected, but they rarely show clinical signs. Calves can regenerate RBCs much faster than the spleen destroys them compared to adult animals.

As with all diseases, prevention is key, and anaplasmosis control starts with controlling external parasites.

Using a salt-mineral mix that has an insecticide included from 30 days before fly season until the first killing frost is one aspect of the multi-pronged prevention plan.

Apply fly tags to all cows, bulls and calves when about 200 horn flies are on an adult cow. This will be from about May 15-June 15 for most of the Farm World readership. Putting insecticide tags in too early decreases their effectiveness. Apply a pour-on to all animals at the same time as you fly tag so you get a quick knockdown of flies.

Walk-through fly control rubs charged with insecticide work very well when placed in areas where cattle must use them. Having a face flap on the mineral feeder is also a great idea.

Ticks prefer to live where grass is tall. Using Management-intensive Grazing where cows are moved every three-seven helps to keep the grass from getting too tall. Clipping pastures can also help.

I am seeing more portable shades used in cow-calf herds, and they help prevent cows from bunching up along a tree-lined fence row, which is prime tick habitat. Cows bunching here are more likely to be infected, and if the neighboring farm also has cows, this is another opportunity for disease spread. Using a temporary electric fence to keep cows out of these areas during peak tick season can help a lot.

We need to adopt the one-needle, one-cow rule. We can spread not only Anaplasmosis, but also other diseases. The same goes with palpation sleeves. We need to use 1/cow. If we use castration knives, dehorners, implant guns or tattoo pliers, we need to disinfect them between animals. One ounce of chlorhexidine to 1 gallon of water is a typical ratio for disinfecting equipment. Disinfection takes two-five minutes, so having multiple instruments in multiple buckets is a good idea.

Every time I speak with a veterinarian or producer who is dealing with an anaplasmosis outbreak, they ask me two things. Should they feed chlortetracycline, and what about the vaccine?

In both cases, consult your herd health veterinarian. They know the most about the disease in your specific area.

Feeding chlortetracycline in a free-choice salt-mineral mix is not a complete control plan for anaplasmosis. Numerous research trials show that up to 20 percent of beef cows on pasture consume little to no salt-mineral mix when it is offered free choice.

An experimental vaccine is on the market and approved for use in 30 states. Your herd health veterinarian can advise you whether it is approved and whether they recommend its use. It is imperative to know that the vaccine does not prevent the disease. It successfully primes the immune system to reduce or even eliminate clinical signs in newly infected animals.

I recommend blood testing all cows and bulls in the herd before considering use of the vaccine. It is crucial to know the level of infection before you start vaccinating.   

Anaplasmosis can be a devastating disease. If it is in your herd or area, you need a customized prevention plan developed in partnership with your herd health veterinarian.