Two types of diseases have vaccinations.  One is a vaccination for diseases that can kill, and the other is for diseases that can make you sick.  Always vaccinate against diseases that can kill you.  Prevention is always better for both, but vaccination is the way to go with diseases that cause death.  Prevention is always better for the diseases that make you sick.

Another concept I apply to vaccinations is determining if you have an open or a closed herd.  A closed one is where the horses go nowhere beyond the farm’s boundaries, and no strange horse comes in.  Leaving for a horse show, a hospital visit, or a clinic is the definition of an open herd.  Adding new horses or boarding at a boarding barn where horses come and go is also an open herd.  Closed herds need vaccinations against diseases found on the farm, such as tetanus and rabies. Also, consider Potomac horse fever (PHF) and the encephalitis diseases transmitted by insect vectors on closed farms.  Also, consider botulism and anthrax if in your area.  But closed farms do not need to consider strangles, flu, rhino or other communicable diseases that cause illness, but usually not death if handled correctly.

In horses, the diseases to absolutely vaccinate for are the deadly diseases tetanus and rabies.  Worth considering in this group are the encephalitis diseases of EEE (Eastern Equine Encephalitis), WEE (Western EE), VEE (Venezualan EE) and West Nile Virus (WNV).  All of these can kill, with tetanus and rabies being everywhere.  Additionally, if your horse contracts rabies, he can give it to you, and you will die.  Only one person on record has survived rabies.  A rabid horse exposed me to this virus, and I went through the post-exposure protocol.  Vaccinate every horse you have for rabies, and do not argue this with me.  I have only seen one horse die of tetanus, and there is no reason not to vaccinate your horses for this.  Again, please do not argue with me on this.

Encephalitis diseases can kill your horse, but they only occur during the mosquito season.  Most governments have sentinel birds tested daily for this primarily avian disease.  If they detect it, they sound the alarm, and if found in your area, vaccination against this disease is warranted.  The horse is a “dead-end host,” meaning that the virus doesn’t belong in the horse.  It lives in birds, but if a mosquito bites an infected bird and then bites a horse, they will become very sick and many die.  In humans, the WNV also jumps from birds to horses and humans, so you will hear if WNV is occurring in the human population.

All the other vaccinations for horses will protect in varying degrees but avoiding exposure is a better course.  These include strangles, influenza, equine herpes virus and Potomac Horse Fever (PHF).  Avoiding new horses coming into a group is effective.  Avoiding a common drinking source is effective for strangles. Botulism is endemic in certain areas’ soil, so base this vaccine on the local vet’s recommendation.  Anthrax is also a local disease, so follow your vet’s advice.

Potomac Horse Fever is a seasonal disease that has spread across America.  Listen to your local vet’s recommendations; if unvaccinated, know the first signs of this disease and treat them with antibiotics.  When this disease first appeared, the tell-tale sign for me was a horse avoiding his sweet grain but eating the hay as if nothing was wrong. This unusual behavior occurred before any diarrhea had started, and it was also July through September in New York, the endemic months.

Equine Viral Arteritis (EVA) is another vaccination you should consult with your vet before giving to breeding stallions. But once vaccinated, the tested horse will be EVA positive forever, complicating many breeding programs. Breeding organizations require a negative EVA test; thus, the positive stallion will be excluded.

There are two parts to current vaccines: the antigen and the adjuvant.

The antigen is a piece of the bacteria or virus or a killed or attenuated virus.  The antigen is the part that activates the innate or cellular response.  You can call these the immune system’s first responders and include T-killer cells and groups of inflammatory molecules called cytokines.

The adjuvant is a compound that intensifies the antigenic response without creating the disease.  It stimulates the adaptive or humoral immune system producing the immunoglobulins that will remember the antigen and mount an attack on any future antigen invasion.  A vaccine aims to protect the horse from a future illness caused by a specific disease through the adaptive immune system.

The more lethal the disease is, the better the response of the adaptive immune system to target and destroy the pathogen.  The weaker the disease or the more variants the pathogen has, the poorer the adaptive response to the disease.  Variants in viruses are why no vaccine is effective for AIDS or hepatitis C in humans.  Antigenic drift is why vaccines need boosting for diseases such as influenza and EHV.  Only time will tell if a vaccine will be effective against a constantly changing SARS-CoV2 (COVID-19).

A nano-vaccine against the new disease called COVID-19 is available for the first time.  Here the adjuvant is being eliminated as more but smaller (nano size) antigens are being used as both the antigen signal and the humoral response boost.  When writing this, a vaccine for COVID-19 is now rapidly developed.  It is a new technology that may be more effective and have fewer side effects that worry so many against using vaccines. Unfortunately, the lengthy safety tests are shortened in a rush to manufacture this new vaccine.

Vaccination reactions, including stiff necks and fever, are common after injection.  Many vaccines are intranasal (sprayed into the nasal passage), making sense for any virus invading the upper airway.  In SARS-CoV1, the virus only inhabited the upper airway and was quickly eliminated by the immune system.  However, SARS CoV2 occupies the upper and lower airways and can have a more devastating effect on the respiratory tract. Therefore, an intranasal vaccine may not be effective for this disease.

When I practiced and administered intramuscular vaccine injections, I rarely had sore necks or horses with fevers.  I attribute this to shaking the vial like crazy, then drawing up 3 ml of the vaccine and injecting it back into it repeatedly until I resuspended all the settled sediment in the bottom corners of the vial.  I then drew up the required dose and immediately injected it into the muscle.  If more than a minute had passed from drawing it into the syringe, I again drew air into it, shook it like mad, expressed the air, and immediately injected it.  If a vaccine came preloaded into a syringe (not from a multidose vial), I would also draw air into it and shake it. Then I would express the air and inject the vaccine.  Injection reactions were so rare that I can’t now remember any.

Another tip I would offer is to always give a vaccine for an “R” disease, such as Rabies or Rhino, on the Right side of the neck.  Then, if there is a reaction, you know which vaccine caused it.

Another tip is to avoid vaccines with multiple diseases in one.  Unfortunately, it is hard to find vaccines with tetanus alone, so I found one vaccine with tetanus combined with the encephalitis diseases (EEE, VEE, WEE, WNV) all in one is OK.  Just shake.  ALWAYS give rabies as a separate vaccine and never combine it with others.  It is a too important disease with horrible consequences for both you and your horse.

I never give more than two vaccinations at a time, each with minimal diseases in the syringe.  Giving too many diseases at once overwhelms the immune system.  I know this requires multiple visits from the vet or better record keeping on your part but giving tetanus, rabies, EEE, WEE, WNV, flu, rhino and PHF all at once is unreasonable.  One of the driving forces behind multiple disease vaccines is their sale to veterinarians.  Every spring, I was approached by a vaccine manufacturer with offers to purchase their new multi-disease vaccine. If I bought so many units, the price would drop substantially, or they would add free goods worth thousands of dollars, all with delayed billing. I could have vaccination specials to develop income to pay for it all.  “Marketing before the health of the horses is not what I do,” I would tell them.

The key points for horse vaccinations are:

• Do them for diseases that will kill your horse.
• Do them judiciously if you need protection (open versus closed herds).
• Avoid diseases by quarantining new arrivals.
• Shake the vaccine vial like crazy before injecting them.

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