How can you tell the difference between bovine respiratory disease (BRD) and endotoxins? Well, you can’t. With similar side effects, endotoxin events may be more widespread than anyone knows.
Many BRD wrecks, blamed on the lack of vaccine efficacy, may actually be the result of an adverse endotoxic event. The classic scenario that I see repeatedly is that a producer vaccinates the calves. At first, they look good and then the next day, they are depressed and not wanting to eat. The producer simply thinks that the vaccination program was really hard on them. Then, the producer questions whether to go back into the group of calves and treat each one or wait it out. Most of the time they wait it out, and the health of the animal appears to be better. It’s a couple of weeks later when we experience the BRD wrecks.
Endotoxins are part of the cell wall of gram-negative bacteria. They can make the immune system unable to respond correctly. When this happens to a certain degree, the animal is immunocompromised and can’t respond properly to the vaccine or BRD agents, like viruses and bacteria. The two-to three-week window between vaccination and the BRD outbreak is simply the incubation period for the viral and bacterial agents the calves were exposed to during the endotoxic event. The endotoxins act as a mediator of shock, and depending on the amount of stress and type of endotoxin, these reactions can be mild to severe. If cattle get enough endotoxin, they can even collapse and die. High temperatures and humidity along with stress tend to make endotoxic reactions worse.
When a producer administers too many gram-negative vaccines at one time, the cattle may have an endotoxin reaction and wind up in a BRD wreck three weeks later. This is the most common response to overexposure of a gram-negative vaccine, such as pasturella, homopholis, salmonella and pinkeye.
Be suspicious when you use one or more gram-negative vaccines and start to see higher than normal morbidity rates or respiratory problems (BRD) two to three weeks post vaccination. If the producer is using any gram-negative vaccines and has seen the above scenario, he should re-evaluate his vaccination program with his veterinarian.
The key takeaways are that you should be keenly aware of the number of gram-negative vaccines that you give and to be sure that you’re handling those vaccines (and all vaccines) properly. Any vaccine made with fetal calf serum will have some amount of endotoxin. Prevention and proper vaccine handling are the only steps you can take to prevent an endotoxin outbreak.