Theileriosis vs. Anaplasmosis
If you are not sure, test. Theileriosis and Anaplasmosis have very similar symptoms. Because Anaplasmosis is caused by a bacterium, it can respond to antibiotics. Theileriosis, on the other hand, is caused by a protozoan parasite and no amount of antibiotics will affect it.
“ The first things we see, which are our canaries in the coal mine, are animals going off feed and dropping weight very quickly,” Dr. Olds said.“ They have a fever, you’ ll often see coughing or a head hanging. They have labored breathing and are very lethargic.”
With Anaplasmosis, it’ s the opposite of lethargy— animals can get agitated and a little bit aggressive.
what some vets see happening in Missouri. So, I don’ t think we have a full understanding of what Theileria does within a cattle herd because we’ re seeing these regional differences,” Dr. Herman said.
Work with your veterinarian to develop protocols in line with what’ s happening locally. And given those regional differences, know that the situation is fluid.
“ Basically, it’ s ever-changing,” Dr. Herman said.“ You have to adapt to whatever the risks are.”
What to Do
Stress is often the tipping point for bad things to happen with Theileriosis, the two experts agree. That’ s particularly true when naive cattle are initially infected. Just riding through your cattle and checking them is not enough stress to cause a problem, but Dr. Olds said,“ It’ s things like calving, weaning, branding, being put on a truck.”
To that end, low-stress handling is a must. Also, provide plenty of quality water and feed to give the weakened immune system and blood supply as much opportunity as possible to keep the animal going.
Once an animal becomes infected with Theileriosis, it is a carrier for life. For the most part, these animals won’ t show any symptoms until a stress event occurs. Then the disease can rear its ugly head and symptoms can appear.
Here’ s the bottom line: Asian longhorned ticks and Theileria are here to stay and will continue to spread from east to west.
Dr. Olds said,“ Once the tick and the pathogen were here, it was inevitable that many producers would eventually get it at some point. It’ s not going to go away, so we have to start managing it and moving forward.”
Then There is Screwworm …
In contrast to the Asian longhorned tick and Theileriosis, the NWS and its flesh-eating larvae are more straightforward to handle. But that does not make them any less insidious.
“ The New World Screwworm fly generally affects a single animal within the herd, so it’ s an opportunistic parasite,” Dr. Herman said.
All the fly needs is an open wound where it can lay its eggs, and the wound does not have to be very big. Even a tick bite can become an opportunity for larvae to develop.
That makes any warm-blooded animal a target. Particularly concerning are deer and feral hogs and, in Texas, exotic game animals. A coordinated effort between wildlife agencies and domestic livestock groups on the state and federal levels is in place in South Texas.
Once the larvae appear, they burrow into living tissue, causing pain and even death if left untreated. Two products are conditionally approved for treatment and prevention of NWS larvae. There are a number of products available to treat screwworm larvae infestations and more will likely be approved in time. For a complete list of products, see the QR code in the ' For More Information ' section.
In the near term, producers concerned about NWS can inspect facilities and remove any hazards that might cause a scratch, scrape or cut, then treat any they find.
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Asian longhorned tick. New World Screwworm. 14 NATIONAL CATTLEMEN DIRECTIONS 2026