This is about Lyme Disease in Horses: Causes and Treatments

Lyme disease or Lyme borreliosis is a parasitic disease vectored by ticks on horses. It is present worldwide. It affects humans and domestic mammals; it is a zoonosis (disease transmissible from animals to humans). Different symptoms are depending on the species affected. The typical form described in humans is not the same as that described in animals, we will see the major differences. Currently, it is a disease sought in the context of “Piro-like” type blood investigations. The diagnosis and treatment of Lyme disease in horses will be detailed below.

Lyme disease agent and its vector

The causative agent of Lyme disease is a bacterium of the order Spirochetales (same order as for leptospira: agents of leptospirosis), a spiral, a motile bacterium of the genus Borrelia. It should be noted that Borrelia burgdorferi is the bacterium identified at the origin of the disease.

The transmission of this pathogen is via a vector: the tick. Note that the main vector is Ixodes Ricinus in Europe. It is a small-sized biting arthropod ranging from three millimeters to one centimeter. These agents are found preferentially in wetlands and forests. Lyme borreliosis is an infectious disease but not contagious that it is not transmitted from individual to individual.

Clinical aspects of Lyme disease in horses

Lyme disease was first described in humans. Indeed, the specificity of the symptoms and the importance of the clinical form have been a real research engine to prevent and treat this disease. The following table lists the different clinical signs. Note that in the horse the clinic is not as obvious and that very often the correlation with Lyme disease is not conclusive. It is possible, as in many pathologies, to have certain clinical signs and not others.

Is Lyme disease in horses over diagnosed?

After having seen the multitude of possible symptoms in horses, we are going to address a rather important question concerning this disease and whose existence cannot be ignored: Is Lyme disease over diagnosed in horses?

Indeed, we will discuss the diagnostic elements very soon, however, studies have shown that Lyme disease is often diagnosed by a single test. The latter can present many false positives and false negatives (that is to say an erroneous diagnosis of the disease). According to the researchers, it would be necessary to combine several tests to affirm the diagnosis of certainty.

It is important to add that the treatment of Lyme disease (assuming a positive response to the latter) involves the use of antibiotics from the Cyclin family. These antibiotics have anti-inflammatory properties. It is therefore difficult to conclude as to the origin of the attack, its possible improvement, and a positive test for Lyme disease.

Diagnostic elements of Lyme disease in horses

The diagnosis of Lyme disease in horses requires the analysis of different elements: clinical signs, epidemiology, and biological research of the bacterium.

Two tests are then commonly carried out:

PCR or “polymerase chain reaction”: searches for sequences of the bacterial genome in the samples.

ELISA test: it is an indirect serological test that involves the search for anti-B. burgdorferi antibodies in the serum. It is a sensitive test but lacks specificity, hence the appearance of many false positives.

Cultures and research of bacteria in the samples are also possible but less practiced.

Treatment and avoidance of Lyme disease in horses

Currently, the treatment of Lyme disease in horses essentially involves the use of antibiotics from the Cyclin family (Oxytetracyclines and Doxytetracyclines). The treatments (dosage and duration) are set up by the veterinarian after the results of the blood tests very often. The follow-up must be rigorous because these molecules have digestive side effects that can cause significant disorders.

Regarding prevention, there is currently no vaccine with marketing authorization for horses. To guard against so-called “Piro-like” diseases, it is important to monitor horses closely. The elimination of ticks on the animal, avoid putting the horses in meadows contaminated by ticks, and scrutinize the horse when returning from a ride. Unfortunately, today, there are no antiparasitic powerful enough and resistant enough to limit tick bites on horses.

The prognosis of horses with Lyme disease

For all horses without clinical signs or specific organ damage, the prognosis is good. However, for horses with major joint or neurological disorders, the sporting prognosis is much worse.

Currently, researchers and veterinarians are struggling to position themselves regarding the relevance of the diagnosis and its clinical correlation. There are many clinical forms of the disease, but everything that is not “diagnosed” cannot be “Lyme disease”, this is an important nuance to consider.

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