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Anthrax: More Than A Bioterrorism Weapon, Just As Deadly For Horses

Most people know anthrax as a bioterrorism tool, but it can also harm livestock. Anthrax occurs naturally as a spore-forming bacterium in the soil in many parts of the United States. Once it is ingested or inhaled by an animal, the bacteria travels to lymph nodes, where it multiplies and circulates throughout the body.

Anthrax infection often gives no warning, making it an especially deadly disease. Though cattle are most often affected by the disease, horses can also be infected with anthrax. Horses that work with cattle, in competition or on a working ranch may be more at risk of anthrax exposure, according to a recent report by Quarter Horse News. Horses that live in cattle-abundant states, like Texas, may also be at additional risk of getting anthrax. Anthrax can remain viable in the soil for years if left undisturbed.

Anthrax has its deadly effects by not allowing blood to clot. Horses infected with anthrax may have a high heart rate, show signs of colic, and go off their feed. Some horses will have swelling, stagger while moving, or have seizures. Horses generally die between two and four days after developing anthrax signs and are usually diagnosed post-mortem.

If handlers suspect anthrax is the cause of a horse's illness, animal health officials should be notified because humans can contract anthrax through inhaling spores or through cuts in the skin.

Anthrax outbreaks often take place in areas that have alkaline soils or those that are exposed to extreme weather events, like drought followed by flooding. Wet winter weather followed by a dry spring and then heavy rainfall are perfect conditions for anthrax to thrive. Pastures with poor drainage and lots of organic matter are particularly at risk.

There is an anthrax vaccination available, but horse owners should discuss their horse and management strategies with a veterinarian before administering the vaccine, as there are other ways to prevent anthrax outbreaks. Horses living in anthrax-prone areas could be fed off the ground if conditions seem ripe for an anthrax outbreak. If horses have traveled through mucky areas or through areas where cattle have been, washing them with soap and water may lower anthrax risk.

It’s Everywhere: Why Tetanus Vaccination is Imperative

A trip to the doctor or emergency room may prompt the question “When was the last time you had a tetanus shot?” Though some will have to think back to their last injury for that answer, when asked about a horse's last tetanus booster, the answer should be immediate: annually.

Tetanus is caused by a spore-forming bacterium that is present in the intestinal tract of horses, humans and other animals. It also lives in the soil, where it can be viable for multiple years, posing an ongoing threat to people and horses, which are the most susceptible animal to tetanus.

The bacteria can enter a body through even small open wounds, cuts or incisions, but puncture wounds are particularly susceptible, especially to the sole of the hoof. Infection can also occur through gastric or intestinal ulcers after eating contaminated soil or feces. Foals can also become infected through their naval as the umbilicus heals. The fatality rate for horses who contract tetanus is 75 percent, so vaccination is imperative.

A horse with tetanus will be overly sensitive to noise and movement. As the disease progresses, the horse's third eyelid will prolapse, his nostrils will flare and he will adopt a “sawhorse” stance, with rigid muscles and a tail held away from the body. Most affected horses will eventually have respiratory failure and die.

Tetanus is completely preventable through vaccination, which is considered an AAEP core vaccine.

Anthrax And Equines: A Deadly Combination

Though anthrax may be more familiar to people for its use as a biological weapon, the bacteria should also be a concern to equine owners for the potential harm, including death, it can cause to their animals.

Bacillus anthracis, the bacteria that causes anthrax, can lie dormant in soil for years; it is particularly hardy in alkaline soil. If anthrax spores are inhaled or ingested, or if they encounter a wound, horses can develop and anthrax infection. Ingestion is the most common way for horses to get an anthrax infection. Ingestion often occurs after a heavy rain, when anthrax spores are pushed to the surface of grass; it can also occur during drought conditions when grasses are eaten down to the soil.

Once anthrax enters the body, it becomes active and multiplies rapidly, causing toxins that spread throughout the body. The septicemia anthrax causes progresses rapidly; killing many affected animals within two to four days.

Horses with anthrax will have trouble breathing; they will also have a high fever, and swelling on the neck and chest. Affected horses may colic, have bloody diarrhea or have seizures. The disease can be spread to humans, so an anthrax infection must be reported to the state's veterinarian.

Anthrax is not endemic to all parts of the United States, so the vaccine is recommended only for horses that live in areas that are known to have anthrax spores. It is a live vaccine, so reactions to the injection site may occur. Antimicrobials may interfere with the vaccine response, so they should not be administered at the same time.

Read the AAEP's anthrax guidelines here.