Spring preparations: equine vaccines and deworming
for Tri-State Livestock News
When the snow starts to melt and the ground begins to thaw, pastures begin to look alive again with green grass and water flowing through drainages; but with all this new life come the parasites and bugs from which livestock and horses need to be protected. Horse owners should be prepared for warm weather by deworming and vaccinating their horses against deadly diseases, many of which can be easily transmitted through insects, soil and drinking water. With all of the vaccines and dewormers available, though, many horse owners don’t know where to begin. Over-vaccinating horses can cause undue strain on a horse’s immune system and owners unnecessary strain on their wallets. To help sort through some of the confusion, Dr. Liz Boos from the Belle Fourche Veterinary Clinic, Belle Fourche, SD, provided Tri-State Livestock News readers with some helpful tips.
The most important thing to note about vaccines is that there is not a universal answer. Dr. Boos explained. “It seems like there should be a one-size-fits-all answer, but there isn’t. We [veterinarians] try to look at what the horse is going to be doing.” Veterinarians will ask horse owners a series of questions regarding their horse’s lifestyle, activities and travel to try to determine the best combination of vaccines to protect your animal.
Dr. Boos recommended that an average horse that stays in one location and doesn’t see a lot of other horses have the following “core” vaccines (disease information supplied from http://www.bfvetclinic.com):
1. West Nile Virus (WNV): WNV is carried by mosquitoes. Horses infected with WNV may appear uncoordinated, sensitive to noise, and, in severe cases, unable to stand. Vaccines are commonly available in a singular form, but are sometimes available in combination shots.
2. Eastern & Western Encephalomyelitis (Sleeping Sickness): Eastern (EE) and Western (WE) Sleeping Sickness is carried by mosquitoes. Infected horses may appear dull or “sleepy.” The Eastern form of this disease is the most deadly, with only a 20 percent survival rate. EE and WE vaccines are typically given in combination with other vaccines in a “4-way” or “5-way” shot.
3. Tetanus: Tetanus is a toxin produced by Clostridium tetani, a bacteria that lives in the soil. Symptoms include overall muscle rigidity, often causing a “saw-horse” stance. Another symptom is third eyelid prolapse. Vaccine causes an immune response to the toxin produced by the bacteria and can be found in common “4-way” or “5-way” combination vaccines.
4. Rabies: Rabies is a virus that is passed through saliva from bite wounds. The virus can be passed to people through handling bits and anything else the horse may slobber on. An infected horse will show strange behavior, such as fear of water or standing away from the group, and may or may not exhibit excessive salivation. All horses that show signs of rabies will die from the disease within 10 days. Rabies vaccine is not available in combination form, and must be given by a veterinarian.
“Most people always think of dogs and cats for rabies,” said Dr. Boos, “But it [infected horses] does happen. Rabies is a deadly disease and it’s a very effective vaccine. No live vaccine is 100%, but the rabies vaccine is about 99 percent.” Dr. Boos commented that many horse owners vaccinate for rabies in the fall to space out the number of vaccines given to their horse at one time.
Many horses have a mobile lifestyle and travel with their owners to shows, rodeos, and events. For these horses, Dr. Boos recommended vaccinating for the following diseases (disease information supplied from http://www.bfvetclinic.com):
5. Rhinopneumonitis/Herpes (Equine Herpes Virus [EHV]): EHV is spread in two different forms. EHV-1 is the neurologic form, EHV-4 is the respiratory form, and either can cause abortion. Not all vaccines prevent both forms. Intranasal vaccines allow for local immune stimulation helping to prevent the respiratory and (depending on the vaccine) the neural form. Injectable forms provide a more systemic response, helping to prevent abortion, and can be found in combination vaccines. Approximately 70 percent of horses have been exposed to EHV and may be carriers of the disease. Shedding of the virus may occur without obvious symptoms in the horse.
6. Influenza: “Flu,” not to be confused with EHV, is a respiratory disease only. High fever and coughing are common signs of flu, as well as nasal discharge. Vaccines are often intranasal to provide better immunity in the area needed (nasal passages and back of the throat), but can be found in combination vaccines as well.
Strangles is a vaccine commonly requested by barns where large numbers of horses are housed. Dr. Boos does not consider strangles a core vaccine and recommends vaccination on a “case by case” basis. Strangles is caused by the bacteria Streptococcus equi and can be passed through nose to nose contact, contact with nasal discharge from an infected horse, or equipment/walls of a barn with a known strangles outbreak. Symptoms include fever, depression, heavy nasal discharge and swelling behind the jaw. Vaccine is only available in intranasal form and should be boostered after three to four weeks. Strangles vaccine should not be given at the same time as other intramuscular vaccines as abscess formation at the injection site is common.
Deworming is a task that every horse owner is familiar with but Dr. Boos states new research shows owners may be able to back off six-week deworming rotations, and instead, initiate regular fecal screenings. She added that veterinarians can now work towards saving people money by backing off heavy deworming schedules that can also increase resistance in parasites. “Fecal egg counts will show who the high shedders are,” Dr. Boos advised, “Bring in a fecal sample that is somewhat fresh and label with the horse’s name. Your veterinarian will look at it and, depending upon what they find, determine what type of dewormer the horse will need.” She described that in many situations, only one or two horses in a herd will have a high parasite load. These horses shed parasite eggs, infecting the rest of the group and are labeled “high shedders.” They will often require follow-up fecal screenings and heavier doses of dewormers. Dr. Boos still recommends deworming horses twice a year (spring and fall) with ivermectin/moxidectin to cover most parasites and once with praziquantel to treat tapeworms, which can be a cause of colic.
In short, there is no single vaccine or dewormer to cover every horse’s needs. Remember to select a health plan that will best protect your horse. There is a plethora of vaccines and dewormers available to consumers today which can cause an information overload. But not to fear, your veterinarian is generally the best reference and only a phone call away.
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As a routine management matter, the Teddy Roosevelt National Park plans to remove a few horses from its herd.