An allergic reaction to vaccination can be mild and local (temporary swelling at the injection site) or fatal if the animal goes into anaphylactic shock. Janice Berg, director, veterinary affairs with Merck Animal Health in Kirkland, Quebec, says clostridial vaccines commonly produce local reactions. A large reaction can make the neck sore for a few days if the injection was in the neck.
“If the animal is very sensitive to the vaccine, it can be a large swelling, which might be a concern if the animal is reluctant to move and lame for several days,” Berg says. “If the swelling is near the shoulder, pain hinders shoulder movement when the animal walks. Even if a person injects subcutaneously behind the shoulder, this can impair shoulder range of motion as well.”
The neck is the preferred location for injections, but if it’s covered with mud or manure you need to select a cleaner site. “Administer the injection far enough away from the shoulder (either in front or in back of it) that it won’t interfere with movement if swelling occurs,” Berg says.
Most reactions can’t be predicted or prevented, so it’s important to be prepared.
“It’s wise to have epinephrine on hand, and corticosteroids such as dexamethasone to treat an animal that has an anaphylactic reaction,” Berg says. “It is crucial to treat these as soon as possible, especially if respiratory distress becomes severe, because these animals can quickly die.”
Watch for signs of distress
Monitor vaccinated animals for at least an hour after treatment. Most fatal reactions occur within the first few minutes, but a reaction within the first hour can be life-threatening unless the animal is treated. Typical symptoms include an animal acting abnormally, having difficulty breathing, and possibly drooling saliva.
“There is usually some respiratory distress,” Berg says. Fluid starts to build up in the lungs (pulmonary edema) and the animal basically drowns. The animal may become agitated or anxious because it can’t breathe very well, and there may be muscle tremors and shaking. The animal becomes quite distressed and collapses.
“When you see any of these signs, it is imperative to treat immediately,” Berg says, noting it is important to have a plan in the event an animal has a serious reaction.
“Even if you have a bottle of epinephrine on hand for emergencies, check expiration date and replace it when it gets out of date,” she says. “You might not need it for several years, but if you do, you want it to be effective. Replacing it will be very inexpensive compared with loss of an animal.”
Read the label
Producers should familiarize themselves with label directions ahead of time so they are not trying to find reading glasses to read the fine print while in a panic trying to inject an animal that is about to die of suffocation. Put a piece of tape on the bottle and use a marker to write dosage and route of administration in big print and easy to read.
It’s also important to have the epinephrine in close at hand in a chute-side kit when vaccinating cattle (along with spare needles, transfer needles, pliers for changing needles. There may not be time to run back to the house to get the bottle. It may be too late to save the animal.
If a certain animal has a severe reaction and recovers, be careful when giving that same vaccine again the next season. These reactions tend to be worse the next time, and the animal may die. “That animal is already sensitized to whatever protein antigen is in that vaccine, and there’s risk for this to happen again,” Berg says.
If you multiple vaccines are given at the same time, pay attention for injection-site swellings, and make note of which vaccine was given where. If clostridial vaccines are given on one side of the neck and the live virus injections on the other side, it is easier to determine which injection caused the local reaction.