Anti-infectives’ Role in Healing
Anti-infectives, properly used, can play a part in assuring animal health and well-being.
Producers strive to provide a safe and high-quality food supply and, when necessary, appropriate use of anti-infectives is a vital part of assuring animal health and well-being. When dealing with costly diseases like bovine respiratory disease (BRD), it is important that producers understand the healing process and the science behind the medications they're using as part of that process.
According to Gordon Brumbaugh, Pfizer Animal Health veterinarian and anti-infectives specialist, there are four stages to healing:
1. killing or slowing the infecting agent;
2. cleaning up infected tissue;
3. repairing or replacing damaged tissue; and
4. returning tissue to its healthy, natural function.
"The first of those four steps is the only one that the anti-infective can influence," Brumbaugh said. "The anti-infective works along with the animal's own defense system in this step to start the process of healing. While it is very important, it is not the only step in healing. The rest of healing has to do with natural processes in the animal."
Signs say each animal is different. There can be differences among animals in their ability and time it takes to heal. And, clinical signs can improve even though true healing is not complete. That is why several days to weeks of effective treatment are important. The anti-infective used to treat BRD can help allow the animal's biological processes of healing to proceed if it remains in the lungs long enough.
The severity of clinical signs of BRD is partly due to the infection and partly due to the animal's own response to the infection. Clinical signs used to identify an animal with BRD should resolve during recovery. "It is possible to measure clinically the ability of a medication to help the animal recover — that's called efficacy," Brumbaugh explained. "However, in sick animals, the complexities of healing prohibit measuring how 'fast' the anti-infective contributes to the first step of healing."
Speed of response is a misnomer. According to Brumbaugh, "speed of response" is probably more indicative of how early in the disease process the animal is treated and the severity of the condition, not how fast the medication does its part after administration.
"When we think about ourselves, if we are sick and take medicine, we don't immediately jump out of bed and go fix ourselves a big steak dinner and get back to work like nothing is wrong with us," he explained. "The effectiveness of an anti-infective should be considered in the context of the net effect of all of the factors of healing working together. The medication and the animal must each do their respective parts."
Extended therapy provides an effective option. When developing protocols for control or treatment of BRD, relying on a proven, effective anti-infective that can maintain sufficient therapeutic concentrations at the site of infection is a key factor in ensuring proper initiation of healing. Producers should consider extended-therapy anti-infectives when addressing important diseases like BRD. Most anti-infectives for BRD offer three days of effective therapy, but extended-therapy anti-infectives work with the animal's immune system for seven to 14 days.
"An extended-therapy anti-infective remains at that site long enough to allow the animal to catch up in the healing process and make sufficient progress with the rest of the steps," Brumbaugh said. "Depending on the tissue and the severity of the injury to that tissue, adequate healing may take several days to weeks."
Because the lungs are one of the more delicate tissues in the body, damage to them takes a long time to heal. Complete healing with recovery of function takes longer for lungs than for many other organs. Properly prolonged treatment is important to help reduce re-colonization by bacteria of the already compromised lung.
When using extended-therapy anti-infectives, producers should still monitor the animals to determine if they're getting better, staying the same or getting worse. Brumbaugh recommended that producers discuss with their veterinarians an action plan to address each of the possible outcomes. Not only can veterinarians assist in developing a plan of action, they can work with producers as they manage BRD to understand and capture the full benefit offered by extended-therapy anti-infectives.
"BRD is a complex mix of viral and bacterial agents that need to be addressed with appropriate management practices, including the use of anti-infectives," Brumbaugh added. "Producers need to understand the role anti-infectives play in the healing process and make decisions that will optimize the animal's ability to recover."
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