Adverse Reactions
Some allergic reactions can be treated; here are tips to watch for.
Proper injection sites and techniques can help minimize risks for reactions.
Occasionally cattle react to vaccine or medication, whether injected, applied topically or given orally. An allergic reaction can be mild and local, like swelling at injection site, for instance, or serious and fatal if the animal goes into anaphylactic shock.
Many of the things we administer are foreign to the animal’s body. In the case of vaccines, the goal is for the body to recognize it as foreign and develop antibodies to combat these foreign agents — antigens — in the future. Vaccine enables the animal to create an immune response.
On occasion, the animal may develop an acute allergic reaction to a foreign substance. Reactions range in severity from hives and itching to systemic shock with fluid in the lungs and sudden death.
Trisha Dowling, professor of Veterinary Clinical Pharmacology at Western College of Veterinary Medicine and co-director of the global food animal residue avoidance database (Canadian gFARAD), says the worst type of reaction is anaphylaxis.
“Unfortunately, with severe anaphylactic reactions you don’t have a chance to treat; the animal just drops dead. In a less serious situation, you can treat with intravenous epinephrine, but most people don’t have this drug on hand,” she says.
Vaccines are the worst for adverse reactions, because the immune system is being stimulated, she says. Vaccine reactions also far outnumber reactions to drugs. The most common reactions are to vaccines such as clostridial bacterins that contain whole organisms.
“The next most common causes of allergic reactions are antibiotic injections. In cattle we see more reactions to oxytetracycline than to penicillin. If a cow or calf has an anaphylactic reaction to oxytetracycline, it’s usually not the first injection. It’s usually the second, because they have been previously sensitized to this drug,” Dowling explains.
With severe anaphylactic reaction the animal dies almost immediately. “They actually ‘die off the needle,’” she explains. “If a cow is having a serious reaction, however, she may run out of the chute and fall over dead. With a delayed type of reaction, by contrast, you just see swelling at the injection site, hives, etc., and these can be more successfully treated.”
Some swellings may be huge. Tetracycline, for instance, is very irritating. Sometimes the cow’s neck gets so big you can’t get her in the headcatch, she warns. The carrier for a certain product may also cause irritation and reactions.
“This is often the case with oxytetracycline. If you give the short-acting oxy-tet intravenously (IV) and give it too fast, it causes low blood pressure and the animal collapses. When an animal collapses during an IV injection, it usually recovers quickly. It’s simply an acute collapse and then they bounce back up again. Those products should always be injected very slowly,” she explains.
Local swelling after injection is generally temporary, resolving in a few days.
“If it’s a subcutaneous (SubQ) injection that causes swelling, this will be more visible than swelling in the muscle from an intramuscular injection. The area will be sore and the animal won’t eat as well for a few days, but at least it’s just under the skin. A bigger problem would be tissue damage from an intramuscular injection,” she says.
“For instance, tilmicosin (Micotil®) is very irritating, and labeled only for [SubQ] administration and you expect some swelling. But if you give tilmicosin intramuscularly it creates nasty tissue damage,” she says.
You can prevent some adverse reactions simply by giving the product according to label directions — at proper dosage and in the proper injection sites.
Some products are notorious for creating temporary local swelling and soreness. If you know there is likelihood for soreness, inject a little farther away from the shoulder, when putting it into the neck. Then the swelling/soreness will not inhibit movement of the shoulder as much. Otherwise, it may make the animal so sore it can’t walk.
Editor’s Note: Heather Smith Thomas is a cattlewoman and freelance writer from Salmon, Idaho.