The dreaded tick, the ectoparasite (external parasites) that we deal with from spring to the first frost, can expose us to many diseases.  Ticks are hematophagic, or blood feeders, western black legged tickand feed on the blood of mostly mammals and birds. Because of this they are also a vector, or carrier of diseases.  Most of us are familiar with the most common of these, Lyme Disease.

In horses we are most concerned about another tick-borne disease which can be found throughout the year, Anaplasmosis, formerly known as Ehrlichia.  Anaplasmosis is caused by the bacterium Anaplasma phagoytophilum.  Anaplasmosis is spread by the Ixodes tick (deer tick & Western black-legged tick).  Twenty percent of Ixodes ticks found in areas with horses are found to be infected with Anaplasma phagocytophilum.

Clinical signs for Anaplasmosis do not appear right away in the horse.  It can take up to three weeks after exposure from the tick bite to start showing clinical signs.  The most common indicator is a fever of 102-106°F.  Besides the fever other clinical signs are depression, loss of appetite, limb swelling, and occasionally muscle stiffness.  The severity of symptoms is dependent on the age of your horse and duration of the infection.  If you suspect that your horse has Anaplasmosis, call your local veterinarian.

morulaThere are a several things that your veterinarian will do to confirm that your horse has Anaplasmosis.  The first thing is to collect a blood sample to run a CBC (complete blood count).  In the CBC, the veterinarian will be looking for a low number of red blood cells, low platelets, and low number of white blood cells.   Secondly, they will create a blood smear with the sample, and look for an inclusion body called Morula that will be present in Neutrophils, a type of white blood cell.   However, the presence of the inclusion body usually will not occur until three days after the onset of the fever.  Due to this delay, even with a negative blood smear many veterinarians will start treatment for Anaplasmosis if the horse is exhibiting clinical signs.  Your veterinarian might also advise performing a Chemistry profile, specifically looking at kidney values for your horse.  Due to many horses affected by Anaplasmosis being dehydrated as well as the drug of choice to treat Anaplasmosis being metabolized by the kidneys, the veterinarian will want to make sure that the kidneys are functioning properly.

The course of treatment for Anaplasmosis is most commonly Oxytetracycline and Banamine to treat the fever.  Oxytetracycline is generally given for five days with horses usually responding well.   There is currently not a vaccine for Anaplasmosis.  Checking daily for ticks is the best preventative measure against your horses contracting Anaplasmosis. Anoka Equine also advises using a topical product called UltraBoss which we have found to be an effective method of tick prevention on horses.  Please call us at 763-441-3797 for more information.

Difference from Potomac Horse Fever

Many of the clinical signs for Anaplasmosis are similar to that of Potomac Horse Fever.  This may cause confusion as to which your horse may have.  Like Anaplasmosis, horses with Potomac Horse Fever show clinical signs of fever, depression and loss of appetite.  However, horses with Potomac Horse Fever can develop laminitis, colic and severe diarrhea.  Potomac Horse Fever is caused by horses being infected by the bacterium Neorickettsia risticii.  Horses are exposed to this bacterium by ingesting infected insects like Mayflies and Caddisflies.

Unlike Anaplasmosis, there is a vaccine available for Potomac Horse Fever commonly given in the fall.  If you are in an area that has had Potomac Horse Fever in the past or have low-lying areas of water (swamps or stagnant water) that attract Mayflies or aquatic insects, you should consider adding the Potomac Horse Fever vaccine to your fall vet visit.

If you would like more information on Potomac Horse Fever click here.

By: Katie Jones, CVT (revised 5/16 by PHM)

If your horse is experiencing any of the above clinical signs, please be sure to call your veterinarian and schedule an appointment.



By: Katie Jones, CVT

For many, when they think of rabies affecting their animals dogs and cats are at the very top of that list. Rabies cases in horses are rare, and can be preventable. Horses exposed to the virus are more sensitive and susceptible to the disease.

Rabies is caused by a virus of the rhabdovirus family. Rabies is a zoonotic disease that is spread through the saliva of an infected animal and is easily spread from one animal to another; including humans. It is believed that any warm blooded mammal is susceptible to this awful disease.

With any suddenly rapid progressing neurological signs, rabies should be considered. At onset additional signs infected horses can begin exhibiting are depression, anorexia, and ataxia. As the disease progresses, other signs that may show include:

  • Repetitive twitching

sick horse

  • Hypersensitivity to touch and sound
  • Hypermetria (a condition in which voluntary muscular movement overreaches the intended goal)
  • Proprioceptive deficits (lack of physical awareness of limbs and their placement)
  • Superlibido
  • Regional pruritus (itchiness)
  • Belligerousness
  • Periods of violence interspersed with periods of normalcy or depression
  • Normal, increased, decreased, or absent spinal reflexes

Rabies is a fatal disease with death typically occurring 3-5 days after onset. There are no treatments or tests for live animals. A postmortem test is currently the only definitive diagnosis for rabies. There are vaccinations available through a veterinarian as a preventative for contracting rabies. Horses can be vaccinated as young as three months of age, but must be boostered yearly to continue the coverage. Although the rabies vaccine is not a required in horse, the American Association of Equine Practitioners (AAEP) lists it as part of the core group of annual vaccines. Increased chances of exposure can be linked to:Rabies2

  • Pasturing
  • Presence of wild animals in area
  • Presence of known rabid animals in the area
  • Horse traveling to areas with frequent rabies cases

The number of horses infected with rabies each year in Minnesota is extremely low.  With statistics like this, it is extremely easy to choose not to vaccinate your animals, but with the virus being lethal yet preventable, is it not worth the risk.

Below is a map of Minnesota showing the positive Rabies cases for 2014.



Additional Information:





By: Katie Jones, CVT

IMG_20141212_150637614_HDRTetanus is a disease caused by the organism Clostridium tetani. It affects almost all animals; including humans. Horses are more susceptible to tetanus than any other domestic animal. This is due to their lower natural immunity and they live in environments with a high risk of tetanus.


  • Not contagious.
  • Anaerobic bacteria. Anaerobic organisms thrive in dark environments lacking in oxygen; however, their spores can survive in the environment for years.
  • Disinfectants, heat, or drying can damage the integrity of the organism.
  • High mortality rate.

Ideal environment: Deep puncture wound that includes tissue damage.

Process of Infection:

  • The organism spores live in the soil and enter the body through wounds or incisions. The toxins produced begin to damage the tissue and decrease the blood supply to the infected area.
  • The neurotoxins produced by the organism can enter the bloodstream from the infected site of the body.
  • These neurotoxins tightly bind to specific areas of the spinal cord and brain, preventing the body’s ability to process brain signals. It causes the affected muscles to intensely and persistently contract. Once the neurotoxins attach to the spinal cord there is no medical treatment available to dislodge them and the effects must be allowed to slowly wear off.

Clinical Signs: Once the organism has entered the tissue and is producing toxins, the course of clinical signs can be very rapid.

  • Beginning signs: Colic, vague stiffness, lameness (if the infected area is the limbs), retraction of the lips, flaring of the nostrils, development of a film over the third eye lid, and difficulty opening the jaw.
  • After 24 hours of infection there is generalized spastic activity of the muscle groups that assist in standing.
  • As the disease process continues the horse can develop labored breathing, stiffness in the front limbs, and the jaw can become locked preventing eating and drinking. These symptoms are characteristic of fatal tetanus; however, not all horses that are infected with tetanus progress to this state.

TetanusTreatment: Dependent on the severity of the disease.

  • Early diagnosis is needed to prevent the progression of the disease with the use of a manufactured antitoxin.
  • If the diagnosis isn’t made early, the wound will need to be surgically opened, effected tissue must be removed, and penicillin will be injected into the wound. The wound will ultimately be left open for continued drainage.
  • The horse will remain on a course of penicillin.
  • Supportive care is given to maintain nutrition and hydration.
  • It can take weeks to see an improvement and clinical signs can last months.

Prevention: Tetanus is a nasty disease with an expensive treatment plan.

  • Although the vaccine is not a 100% guaranteed, it has proven to be a successful way of preventing Tetanus. Check with a veterinarian regarding their specific vaccine protocols.
  • Cleaning and bandaging wounds immediately will also help with preventing the development of tetanus.


By: Katie Jones, CVT

The Streptococcus equi bacterial disease causes horse owners to cringe and barn owners to become nervous. “Strangles” is the term used to describe this condition seen in infected horses when the lymph nodes around the throat become large enough to suffocate the horse. It typically occurs in horses 1 to 5 years old.

Causes: Exposure via direct contact with an infected horse or contaminated objects.

Incubation period: 3-14 days

StranglesClinical Signs:

  • First sign of infection is a fever ranging between 103°F-106°F.
  • 24-48 hours after the fever spike: nasal discharge, depression, inspiratory respiratory noise, and difficulty swallowing.
  • The horse may keep their head down and neck stretched out.
  • The lymph nodes become swollen and painful due to the formation of abscesses.

Diagnosis: Confirmed by a bacterial culture collected with a nasal swab.

strangles1Treatment: Under a veterinarian’s direction.

  • Hot compressions to swollen lymph nodes to encourage drainage. If they don’t drain on their own, they may need to be lanced and flushed.
  • Suspected infected horses need to be isolated from others.
  • If the lymph nodes are swollen to the point the horse is struggling to eat, they should be fed a soft diet.
  • Penicillin is an effective drug for treatment. Occasionally, if Penicillin is started before enlarged lymph nodes are seen, the disease process could stop.


  • The abscesses can rupture and drain through the skin, into the throat and nasal passages, or into the guttural pouch. Each of these conditions has different treatment options and complications.
  • The future development of “Bastard Strangles”.
    • Caused by: The infection spreading into the blood stream; thus, traveling to all the lymph nodes of the organs (liver, kidney, intestines, heart, spleen, and brain).
    • Clinical signs: Weight loss, episodes of colic, and a general decline of health.
    • Requires intensive veterinary management to recover.

Prevention: Strict hygiene protocol (quarantine)

  • A barn with a positive case should have everything disinfected which COULD HAVE come into contact with the horse (stall walls, buckets, ect.).
  • Traffic in and out of infected facilities needs to be restricted.
  • Available Vaccine. The immunity from both the vaccine and natural exposure is short lived. This vaccine is recommended if the horse is at a boarding facility or travels to shows throughout the year.
  • Three negative nasal swabs should be obtained before allowing an infected horse to re-enter a herd.

Strangles 2

Long Term Effect: Most horses which become infected will shed the bacteria for approximately a month after recovery.