We get this question quite often, and it would be convenient to combine the treatments to save on an additional call fee. However, we generally recommend against this for a few reasons. One of the drugs we typically use in joint injections is a steroid anti-inflammatory such as triamcinolone or methylprednisolone acetate. These are very potent anti-inflammatory agents, and can cause immune suppression even in the small amounts used in joints. This means that the immune response to a vaccine could be dampened by the steroids injected in the joint, and the horse may not be adequately protected by the vaccine if it is administered at the same time as intra-articular injections. Also, in the case of the intranasal Strangles (Strep equi) vaccine, we are very careful not to have contamination of any injection sites with the snorting of the vaccine after the horse is given this vaccine. If this modified live bacteria is inadvertently injected, it can set up a nasty abscess and this would be particularly devastating if this infection were to occur in a joint.
Most horse people have heard of Strangles, and many have had the unfortunate experience of dealing with an outbreak. The disease, sometimes referred to as “distemper,” is not new—it was first reported in 1251. The disease is highly contagious. Young animals (weanlings, yearlings, and other young stock) are particularly susceptible, however any age of horse can be affected.
This is a very interesting and common question, and there is a little bit of research available to help guide recommendations. The first thing to consider is that sometimes, unpredictably, a horse will have a severe, immediate response to the vaccination such as anaphylaxis. Obviously, being ridden when this occurs can worsen the situation, and would put the rider at risk if the horse were to become weak or wobbly, or even fall. If you are going to ride the horse after a vaccination, wait at least 30 minutes to ensure these immediate adverse effects are not seen. Some clinicians feel that if the horse is ridden lightly after a vaccination, they develop less stiffness at the injection site. However, it has been shown that extreme exercise (for example, galloping sets or race training) in close proximity to a vaccination can reduce the horse’s ability to respond to the vaccine appropriately, therefore the vaccine may be less effective. It seems the exercise essentially acts as a form of stress that reduces the horse’s immune response to the vaccine. The bottom line—while it may be safe (or potentially beneficial) to exercise a horse lightly a little while after a vaccination is given, avoid strenuous exercise.
West Nile Virus was first reported in Canada in 2001, and first detected in a horses in Canada in 2002. West Nile Virus in horses hit the peak of its prevalence in 2003 with 170 cases reported in Alberta alone. Since then there have not been as many cases of the disease in Alberta, and so the question is often raised—do we still need to vaccinate our horses against West Nile Virus?
If a human arrives for an influenza vaccination from a vaccine clinic or pharmacy, one of the first questions asked is, “Are you feeling well today?” If the immune response is actively engaged fighting another virus or bacterial process, the response to a vaccination might not be optimal. Therefore, if your horse demonstrates a nasal discharge, has a mild fever, or is recovering from another medical issue, we usually delay vaccination until their immune system is better able to respond to the vaccine reliably.
Eastern Equine Encephalitis (EEE) and Western Equine Encephalitis (WEE) are both neurological diseases spread to horses and humans from infected wild birds and rodents via blood sucking mosquitos. The disease typically culminates in a profound depression that characterizes these diseases in the late stages, and gives them the common name of “sleeping sickness.” The American Association of Equine Practitioners considers vaccines against EEE and WEE to be "core" vaccines, recommended for all adult horses.
An upper respiratory tract infection or “cold” in a horse, like in a human, can be caused by many different viruses or bacterial infections—adenovirus, herpesvirus (Type 1, 2, 4, 5), influenza virus, rhinitis A or B virus, Strep equi (“Strangles”)—or even a combination of these agents. Horses can be vaccinated against some respiratory pathogens, namely herpesvirus Type 1 and 4, Influenza, and Strangles, but many other viruses especially are not included in the routine vaccinations (much as humans can be vaccinated against influenza but not the common cold). Additionally, each horse’s immune system will respond differently to a given vaccine, and a small percentage of horses will be “non-responders.” These horses do not mount an adequate immune response following even properly administered vaccinations. If your horse develops an upper respiratory infection even when they have received their yearly vaccinations, they could be infected by one of these other viruses (adenovirus, other herpesvirus types, rhinitis virus), or their immune system simply did not respond to the vaccine as well as some other horses.
What vaccinations your horse receives should be dependent on their specific risk of exposure to given diseases. For horses that do not travel to other barns, shows, or arenas, and do not mix with other populations of horse, vaccination against respiratory pathogens that are passed from horse to horse such as herpesvirus, influenza, and Strep equi (“Strangles”) is probably not necessary. However, not all diseases that are commonly vaccinated against do not pass from horse to horse. The bacterium that causes tetanus is ubiquitous in the soil, and enters the body via wounds—no contact with other horses is necessary to be afflicted with tetanus. Other diseases can be spread by blood-sucking insects, namely West Nile Virus and Eastern and Western Equine Encephalitis (EEE/WEE). The source of the virus that the mosquitos carry is not other horses, but rather wild birds. Finally, rabies virus is found in the saliva of an infected animal, and is usually spread by bite wounds from infected bats, skunks, raccoons, foxes, or other infected animals. Although a “pasture ornament” may not require all the same vaccines as an actively competing show horse, we still recommend that they are vaccinated against these diseases that are not spread by horse to horse contact—tetanus, West Nile virus, EEE/WEE, and potentially rabies.
What is in a “3-Way” vaccine? A “4-Way?” “5-Way?” “6-Way?”
We get a lot of questions about these confusing terms! The “3-Way” vaccine has long been used to describe the combination vaccine containing Eastern Equine Encephalomyelitis (EEE), Western Equine Encephalomyelitis (WEE), and Tetanus. For a “4-Way,” add influenza to those three vaccines just listed. A five way provides protection against EEE, WEE, Tetanus, Influenza and Equine Herpesvirus (“rhinopneumonitis”), and a “6-way” contains all 5 components of a 5-Way, plus West Nile. Although there is a combination vaccine that includes EEE, WEE, tetanus, and West Nile, the combination of EEE,WEE, tetanus, and influenza was on the market for years prior to the introduction of the combination with West Nile, so the “4-Way” term is usually reserved for the vaccine containing influenza and not West Nile. Clear as mud?
Contact the clinic and we can help you determine what vaccinations are appropriate for your horse. Stay tuned in the coming days for more information on these diseases and why we vaccinate against them, as well as more answers to your frequently asked vaccination questions.