Although these diseases do not need to be reported in every state, it’s important to know about communal and non-communal diseases in the area. The best treatment is prevention, and you can help make that possible. For further information or treatment options, please contact your veterinarian. 


Strangles is regularly found in young horses but can cause disease in any age horse.6 The bacteria causes infection of lymph nodes (especially of the head and neck) which can cause fever, stridor (noise at respiration), dyspnea (difficulty breathing), anorexia or dysphagia, and large amounts of nasal discharge.6,7 Infection can also cause abscesses elsewhere in the body or potentially fatal immune reactions. Strangles is often transmitted through direct horse-to-horse contact or indirectly from stalls, trailers, bunks, grooming equipment and other frequently used materials.6 Appropriate testing and quarantine of infected horses is very important in preventing spread. Vaccines may be used to help prevent or lessen severity of disease but can also cause complications. Strangles may be reportable in some states. 

Pigeon Fever
Corynebacterium pseudotuberculosis (Pigeon Fever) can be identified in three forms: external abscesses, internal abscesses and ulcerative lymphangitis.8 External abscesses are frequently found on the pectoral region, while internal sores can appear on the lungs, kidneys, liver and spleen.8 The disease is spread from horse-tohorse contact, insects or contaminated soil.8 Treatment options vary by case. 


Lyme Disease
Lyme disease, while non-communally spread, is a prevalent threat throughout the year. The disease is acquired when a tick carrying a bacterium called Borrelia burgdorferi attaches to and feeds on the horse.9 Clinical signs to look for are lameness, soreness or swollen joints, fatigue, weight loss, and low-grade fever.9 Help prevent Lyme disease by performing a daily tick examination and minimizing tick habitat. 

Equine Protozoal Myeloencephalitis (EPM) is a serious and often difficult-to-diagnose disease. EPM cannot be acquired from horse-to-horse contact. The disease is acquired from possums, which acquire the protozoal organism from cats, raccoons and other various barnyard creatures. 10, 11 When an infected possum’s fecal matter is ingested by the horse, sporocysts may enter the horse’s central nervous system, causing severe and potentially permanent neurological damage.11 Clinical signs include but are not limited to ataxia, incoordination, muscle atrophy, poor balance and paralysis of the face, eyes, mouth or nose. 11 Contact your veterinarian about MARQUIS® (15% w/w ponazuril), the first FDA-approved treatment for EPM.12

IMPORTANT SAFETY INFORMATION: The safe use of MARQUIS in horses used for breeding purposes, during pregnancy, or in lactating mares, has not been evaluated. In animal safety studies, loose feces, sporadic inappetence, lost weight, and moderate edema in the uterine epithelium were observed.

For additional information, please refer to the prescribing information or visit