Whether an animal becomes visibly ill depends upon a complex interaction between the host animal, its environment and the agent that makes it sick.
“Visibly” is the key word because those of us that tend to animals know it can sometimes be difficult to tell if an animal is truly under the weather. They may just look a little off.
Sometimes you treat them for a variable time. Sometimes you don’t treat them and simply observe them closely. Sometimes you can run tests and the answer you seek may still not be apparent.
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Treatment options vary depending on the problem.
Antibiotics are usually used for infectious disease. There are two main classes of antibiotics: bacteriocidal drugs that kill the invading bacteria and bacteriostatic drugs that inhibit the organism from reproducing, relying on the host animal’s immune system to get rid of the bacteria.
There are two types within each class: time dependent antibiotics whose mechanism of action requires that a specific amount of antibiotic be present for a certain length of time, and concentration dependent antibiotics that require a certain peak amount of drug to be effective.
Antibiotics don’t work well in all parts of the body. Areas with poor blood supply such as joints and bone are typically difficult areas for antibiotics to reach. Highly vascular areas with good blood supply, such as the lungs, are easily penetrated. The drugs rely on the circulatory system for delivery; otherwise, they must get through the rest of the body’s tissues before reaching their target.
It is also important to remember the maximum amounts of drugs that can be taken before signs of toxicity become apparent.
Choosing the proper antibiotic depends on past experience, knowledge of the organism and location of the problem and the drug’s ability to get to the target. Some organisms that are normally susceptible to a given antibiotic may not be susceptible. Culture and sensitivity tests often confirm this.
You can also consider the vigour of the animal’s immune system, which may or may not be functioning properly.
In reality, treating an animal means the disease process has already started. You are trying to play catch-up to restore the animal to its health status before the disease struck. There may be lifelong health consequences to the animal and economic consequences to the producer. Studies have shown that many animals in slaughter plants have lesions in the lungs, even though caregivers did not report the animal being sick.
A far simpler plan would be to do what you can to prevent the animal from getting sick in the first place. Vaccinations are an integral part of health management, while keeping the animal’s environment low in disease-causing organisms usually means keeping them clean and dry.
Daryl Meger is a veterinarian and outdoors enthusiast in a mixed animal practice in Westlock, Alta.
