In general, the horse industry is over-reliant on vaccines. Don’t get me wrong, vaccines are useful and are an important aspect of an infectious disease control program. However, they are just one tool and they should not be the first line of defense. Rather, I think we need to change our mindset and consider vaccines as a last line of defense.
Why? Vaccination is not 100% effective. Some vaccines are very good, some are pretty bad, and none protect every horse in every situation. Some horses are not protected at all after vaccination. Sometimes exposure to a large dose of infectious agent can cause disease regardless of vaccination status. Sometimes vaccination can help reduce the severity of disease, but not the likelihood that a horse gets sick and becomes infectious.
When I think about disease control, I think about three main areas:
1) Decreasing exposure
- If a horse doesn’t get exposed to equine influenza virus, it won’t get influenza. End of story.
- Decreasing exposure can be fairly easy for some bugs, possible but requiring effort for others, and almost impossible for some. This is the most important overall preventive tool, however, and it should be the first line of defense. A good general infection control program goes a long way to reducing the risk of exposure.
2) Decreasing susceptibility
- Certain things make horses more likely to get sick if they get exposed to an infectious agent. Some (e.g. young and old age, pregnancy) aren’t avoidable, but others are. We don’t have great data about what increases risk, but things like diet change, stress, pain, high grain diets, overall nutrition, antibiotics, and perhaps administration of other substances like anti-ulcer drugs can presumably play a role. Good general management is therefore a key.
- Concurrent disease is also a risk. It’s not always avoidable, but measures to reduce the risk of other diseases (be they infectious or non-infectious) and to control certain conditions (e.g. proper management of Cushings) can help.
3) Increasing resistance
- This is where vaccination comes in. It’s there to help when efforts to decrease exposure and decrease susceptibility have been surpassed.
So, by no means am I suggesting that vaccination isn’t needed. What I’m saying is it needs to be put into context. Too often, when I ask a horse owner about their farm infection control program they say “I vaccinate against...” When I ask what else they do to prevent infectious diseases, I often get a blank stare in return.
A logical vaccination program combined with a well-designed and practical infection control program can have a major impact on horse health, and we need to do a better job implementing more comprehensive infection control programs on farms, rather than piecemeal, reactionary approaches focused on vaccination and often little else.