A Closer Look At: The Whats And Whys Of Equine Vaccines

In this series, we ask some of the equine health questions you've wondered about but were too afraid to ask. Today, Dr. Earl Gaughan, Senior Equine Professional Services Veterinarian with Merck Animal Health, tackles a few common questions about respiratory illness in horses.

We've all heard a lot in the last year about the way vaccines work. What's the mechanism of action for most equine vaccines? (Killed virus vs mRNA, etc.)

Dr. Earl Gaughan: The simple way a vaccine works is to mimic a natural exposure to an infectious organism that can cause disease, and to stimulate an animal or human to develop an immune response such that infection and disease are prevented. The normal mammalian immune system has several ways it responds to these kinds of exposures and threats of disease. The immune system's “goals” are to rid the body of the infectious organism and/or to reduce any potential life-threatening results such that the body can survive.

Among the responses of the immune system are humoral (antibodies) and innate (chemical and cellular) mechanisms. Infectious organisms present antigens which are usually proteins that stimulate these immune responses. Antibodies are the immune system proteins that bind or block these outside antigens to reduce the number and threat these organisms can present. This response takes the body hours to days to reach effective levels. Cellular and chemical production to fight infectious organisms develop rapidly and can be the quick, first responses after exposure to these threats.

“Killed virus” vaccines are just that – a product that contains killed organisms or proteins that typically stimulate humoral antibody responses. “Modified-live” vaccines perform similarly to killed vaccines but utilize a similar organism to the targeted infection that has been altered such that it will stimulate an immune response but not disease. These vaccine products are most commonly administered to a horse by injection deep into muscle tissue. At least one modified-live vaccine can be administered up the nose of a horse (intra-nasal) such that the vaccine itself is placed on the lining of the nasal passage. This stimulates what is known as innate or mucosal immune responses. This is a rapid (minutes to hours) response based on release of chemical and cellular mediators of the immune defense.

Currently, we do not have mRNA vaccines for horses. These vaccines work by entering body cells and stimulating protein production that can reduce invading viral reproduction and entry into host body cells. Long term repercussions of these products are unknown at this time.

Do equine vaccines vary year to year like the human flu shot?

Equine vaccines do not vary year to year. The AAEP-recommended core vaccines against rabies, tetanus, Eastern Equine Encephalomyelitis/Western Equine Encephalomyelitis (EEE/WEE) and West Nile virus remain very effective and should be administered to every horse in every location in North America. These diseases are typically lethal and the vaccines are successful at preventing disease with very few negative effects.

The reason human flu vaccines change each year is the rapid ability of influenza to undergo what is called “antigenic drift” or mutation of the virus to make it more able to infect a host (human). Antigenic drift in horses occurs, but at a much slower pace than what is seen in people. Equine flu vaccines are changed to keep up with evolving strain development, but again, we are fortunate this does not happen at the rate seen in humans. The rate of equine flu strain and therefore vaccine change is more in a five to ten-year window vs. annual. To date, influenza appears to be the only viral pathogen where annual change is monitored in horses. The strains of equine herpesvirus appear to be stable or more slowly changing, although more strains of herpesvirus are being discovered with more sophisticated diagnostic methods, so additional vaccines may be on the horizon for horses. The same can probably be said for some of the other, less commonly seen, risk-based vaccines.

Some horse owners are skeptical of the efficacy of equine vaccines; how well do they really work? 

Skepticism is rational and informed questions are welcomed by equine veterinarians. The vaccines available for horse diseases like rabies, tetanus, Eastern and Western Equine Encephalomyelitis (EEE/WEE) and West Nile virus work very well to prevent these diseases in horses. These vaccines are considered core or essential for a horse's well-being, as they help prevent diseases that are typically lethal. While there is never an absolute guarantee, it is interesting to note that when these diseases are diagnosed in horses, they are most commonly seen in horses that have not been vaccinated or are far past the appropriate date for booster vaccines.

Other disease-causing organisms do not lend themselves to as complete vaccine protection as the vaccines for the infectious neurologic disorders mentioned above. However, these are also far less lethal infections cause by influenza, herpesviruses, and others. Vaccinating for these diseases is considered “risk-based” and is encouraged for horses that may encounter infectious agents at home or during travel. Vaccinating for these concerns is performed to help reduce infections, reduce severity of clinical disease, and reduce spread of the virus, or other organisms. These vaccines can be very helpful and are recommended for most horses in consultation with a veterinarian. 

Why is it important for a horse who doesn't leave home to still get regular vaccinations?

While a horse at home would appear unlikely to encounter disease-causing organisms, these infectious agents can often come to the horse. For instance, rabies is usually the result of a bite from a skunk, raccoon or other carrier; EEE, WEE, and West Nile can be delivered by mosquitos and the tetanus organism is found in soil everywhere. Vaccinating the horse at home is important to prevent these highly lethal diseases.

Vaccinating horses that do not travel for things like influenza and herpes should be done in consultation with a veterinarian. If other horses do travel and come home, or if horses from varied places mix at all, these infections can be transmitted and are typically very contagious. Other, less common, disease entities may not require vaccination unless presence of the diseases occurs locally or regionally, putting the horse at home at risk. Even trail rides with neighbors can expose horses to infectious organisms not necessarily present at home. Again, discussion with your veterinarian is a great place to get the best answers. 

What are some common reasons horse owners give for not vaccinating their horses? 

Sound medical reasons for not vaccinating:

  1. The horse has reacted severely with past vaccine administration
  2. The horse has recently recovered from the targeted disease
  3. Known or potential adverse events/reactions to a vaccine product

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A Closer Look At: Equine Respiratory Disease

In this new series, we ask some of the equine health questions you've wondered about but were too afraid to ask. Today, Dr. Bryant Craig, Equine Professional Services Veterinarian with Merck Animal Health, tackles a few common questions about respiratory illness in horses.

I think a lot of people are familiar with the big, “scary” respiratory diseases like strangles, EHV, etc. — but do horses just get common 'colds'? 

Dr. Craig: With proper care, a respiratory illness in the horse can be mild in nature. There are several lesser-known respiratory viruses that occur in horses. Some of the most common are Equine Adenovirus, Equine Herpesvirus 2 and 5, and Equine Rhintis Virus B. These viruses are milder in their clinical signs and can be found as a co-infection with some of the other respiratory pathogens as well as by themselves.

However, it is important to keep in mind that any mild respiratory illness can quickly escalate into a pleuropneumonia, which can have devastating consequences for that horse, so all of them deserve attention.

What's the first thing an owner should do if they suspect their horse has a respiratory illness?

Dr. Craig: Isolate that animal as soon as possible to minimize transmission to the rest of the herd. Next step is to obtain a temperature on that animal and contact their veterinarian. After proper disinfection, I would advise going through the rest of the herd and making sure there are no additional horses exhibiting respiratory signs.

Diagnostics are important here so that we as practitioners can know what we are dealing with and determine an appropriate course of action for that horse and the premises. With today's technology, next day results are possible to get a diagnosis.

Do those recommendations change if a horse is fully up to date on their vaccines?

Dr. Craig: No. We still want to isolate a sick or suspected ill animal as soon as possible. We can always put them back in their original spot, but limiting contact with the rest of the herd/premise is the best first step. However, a fully vaccinated horse will be a lower risk for transmission than a naïve animal, so keeping those vaccinations up to date are the best management tool for overall disease reduction.

Why is respiratory disease so easily transmissible between horses?

Dr. Craig: The way we manage and house horses today lends itself to a rapid spread amongst a population. Gone are the days when horses were continually moving to new grazing areas and had the benefit of clean environments almost daily. Transportation of animals amongst different locations also plays a large role. Racetracks have a constantly evolving population which lends itself to disease transmission.  Respiratory diseases can be transmitted a few different ways:

  • In a stalled situation, those pathogens can be transmitted via aerosols (coughing, sneezing), personnel moving between animals, or common items such as tack, buckets, or even brushes.
  • Out on pasture, nose to nose contact is probably the most common scenario, but aerosols, water sources, feed troughs, and personnel can still play a significant role.

What are some basic things horse owners can do to prevent outbreaks from these types of respiratory infections?

Dr. Craig: First and foremost is to keep the overall herd and individual health at the highest plane possible through a proper nutrition program, regular deworming, and an appropriate vaccination schedule. The environment we keep our horses in can play a big role as well, fresh air and clean living spaces being a fundamental part of this. Anything we can do to reduce the stress level also goes a long way in reducing disease. This is especially true when transporting them. Frequent breaks, access to water, and good air flow are all keys when trailering. Lastly, a biosecurity program for the farm or stable is necessary to avoid the introduction and spread of disease. This can be done in conjunction with their veterinarian and can make a huge difference in disease incidence and spread.

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New App Allows For Real-Time Equine Temperature Monitoring, Location Dissemination And Data Sharing

Merck Animal Health has announced its strategic partnership with Irish-based technology company EquiTrace Ltd., creators of the EquiTrace™ platform. Through the EquiTrace smartphone app, the entire horse care team can securely update and access each horse's GPS location and medical record in one convenient location. The app also works in conjunction with Merck Animal Health's Bio-Thermo® microchips, allowing horse care professionals to instantly read, graph and monitor a horse's temperature.

“This partnership is a natural extension of our commitment to delivering innovative infectious disease management solutions to support improved horse care,” said Ron McDaniel, Director of U.S. Equine Sales, Merck Animal Health. “By enabling convenient digital temperature monitoring, we're able to make life easier for busy veterinary and farm teams while providing them with tools to help efficiently identify illness and monitor disease outbreaks.”

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EquiTrace, which can be used with individual horses or at large barns, is compatible with any microchip but must be coupled with a Bio-Thermo microchip to access the temperature-sensing functionality. Bio-Thermo microchips measure a horse's temperature within one-tenth of a degree[1] and provide access to a horse's identification. Both the EquiTrace app and Bio-Thermo microchips work with the Global Pocket Reader Plus™ and the HomeAgain® UWSR+ microchip readers, and the EquiTrace app is available for iPhones or Androids. In addition, the Bio-Thermo microchip is compliant with the International Organization for Standardization (ISO) Standards 11784 and 1178 and meets requirements of both the International Federation for Equestrian Sports (FEI) and the United States Equestrian Federation (USEF).

“We are excited to partner with Merck Animal Health to bring EquiTrace to the U.S.; the technology streamlines health recordkeeping, a task that has traditionally been hard to maintain in busy barns,” says EquiTrace founder Kevin Corley, BVM&S, PhD, DACVIM, DACVECC, MRCVS. “The combination of Bio-Thermo microchips with our software enables rapid identification of temperature fluctuations in a horse at the stroke of a microchip scanner. This is essential to managing infectious diseases, such as equine herpesvirus, influenza and strangles. As an internal medicine specialist, I'm delighted to contribute to a novel temperature monitoring system that's effective without stressing the horse or the barn team.”

EquiTrace data is encrypted, and each barn's data is private. The EquiTrace account owner authorizes others to access data securely through the app. All EquiTrace functions are available with no internet connection for easy access at the barn or on the road. New data is synced when the app is opened with internet connection. To download EquiTrace, visit the App Store or Google Play.

Read more here.

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‘By Showing Compassion For One Life, We Can Mend Many More’: Merck Research Horses Find A New Job

Merck Animal Health's equine division periodically conducts research on their product's efficacy. But what happens to the study horses when the research is complete? Click below to find out how Merck made sure the horses used in an EPM study had a soft place to land—specifically one where they would still be helping.

Watch below to see where they ended up.

 

The post ‘By Showing Compassion For One Life, We Can Mend Many More’: Merck Research Horses Find A New Job appeared first on Horse Racing News | Paulick Report.

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