check for DNA but a certain number of organisms must be detected before the test yields a positive result so you may have a false negative. Treatment involves the use of IV oxytetracycline for 3-5 days in a row. This antibiotic should only be given by your veterinarian as going outside the vein may cause permanent damage and giving it too quickly can cause collapse and death! Depending on how quickly your horse responds, your vet may continue with oral medication. Anti-inflammatories are also used to control fever and pain.
Finding those darn ticks are extremely challenging, especially in horses that live outside and rarely come into the barn. Checking the mane, tail, axilla, groin and area under the jaw are essential, because they are typically the hot spots for ticks. Trying to keep grasses mowed and hedges and tree branches pruned back can help, but these are resilient creatures.
In a recent article in dvm360 May 2015 a discovery by George Poinar Jr. found a fossilized tick in amber indicating Lyme disease is older than the human species! He found spirocyte-like cells from Borrelia burgdoferi (the causative agent in Lyme disease) in a 15 million year old amber-encased tick! Scary!
As of now, there are no great tick repellants on the market. Some researchers are using Vectra 3D for dogs in horses on a trial basis. Hopefully, we will have more information available in the near future. Until then, we must continue to monitor our horses for signs of tick bites, symptoms of disease and strive for proper property and landscape management.
Lyme (Elisa, Western blot, Multiplex test) may be run. I prefer the Multiplex test offered by Cornell as it checks for outer surface proteins indicating whether there has been no exposure, new infection with rising titers or an old infection that has resurfaced. After interpreting the results your vet may place your horse on Doxycycline or Minocycline for 1-2 months duration. I usually add a probiotic to try and keep the good organisms in the gut. Antibiotics, if used improperly can result in fatal colitis!
Anaplasmosis (formerly known as Ehrlicia equi) is also spread by ticks leading to high fever, anorexia, depression and in some cases swollen legs. Anaplasma is not contagious and may have a more seasonal pattern in parts of the U.S. and usually responds quickly to treatment.
Again, a CBC including a platelet count (the cells that help clot blood) can clue you into a probable diagnosis, as the white blood cells as well as the platelets may be low. A PCR test can check for DNA but a certain number of organisms must be detected before the test yields a positive result so you may have a false negative.
ACTHA Monthly | June 2015 | 45