2018: MEDICAL AND SURGICAL MANAGEMENT OF A CASE OF CHRONIC MASTITISIN A MARE


 

Medical and surgical management of a case of chronic mastitis in a mare 

College of Veterinary Medicine, Auburn University, Auburn, AL 
 
A 9-year old American Paint mare was presented with an enlarged right mammary gland of 

greater than one year’s duration. The owner reported that the mare had been lactating since her last 
foaling three years previously. During examination, a thick cream-colored substance was expressed from 
the right mammary gland. Culture and Gram stain were negative for bacteria but a large number of 
degenerative neutrophils were present on cytology. The mare was diagnosed with galactorrhea and 
mastitis. Treatment was initiated with daily milk removal and instillation of intramammary ceftiofur 
(Spectra-Mast®) for four days. The mare responded to treatment with resolution of mammary 
enlargement. Nine months later, the mare returned with a large plaque of ventral edema. Ultrasonography 
of the ventral abdomen revealed enlarged inguinal lymph nodes and fluid accumulation with diverse 
echogenicity within the mammary gland. Cytology of fluid from the mammary gland showed suppurative 
inflammation and bacterial culture revealed Nocardia organisms. Bilateral mastectomy was performed 
under general anesthesia due to the history of chronic mastitis and failure of medical management alone. 
An hourglass-shaped incision was made, and blunt dissection was used to separate the gland at the body 
wall. Postoperative care included systemic antibiotics, flunixin meglumine, and hydrotherapy. Despite 
careful management, complete dehiscence occurred seven days later and the wound healed via second 
intention. At recheck examination seven weeks later, the surgical site was free of drainage and healing 
was adequate. This case documents an atypical case of mastitis in a mare. Generally, mammary gland 
problems in the mare are uncommon.1 The most common signs are swelling, heat and ventral edema, and 
the most common organisms isolated are Streptococcus spp.2,3 Cytology and bacteriological testing are 
recommended to rule out other causes, such as trauma and neoplasia.4 Medical management may include 
milking, intramammary or systemic antibiotics, hydrotherapy, or surgical excision as a last resort. 

 
Keywords: Equine, galactorrhea, mastectomy, mastitis 

References 
1. McGladdery AJ: Differential diagnoses and treatment of diseases of the equine mammary gland. Equine Vet Educ 

1998;21:266-268.  
2. McCue PM, Wilson WD: Equine mastitis- A review of 28 cases. Equine Vet J 1989;21:351-353. 
3. Smiet E, Grinwis GC, van den Top JG, et al: Equine mammary gland disease with a focus on botryomycosis: a review 

and case study. Equine Vet Educ 2012;24:357-366.  
4. Brendemuehl JP: Mammary gland enlargement in the mare. Equine Vet Educ 2008;20:8-9.  

Clinical Theriogenology • Volume 10,  Number 3 • September 2018349

L.M. Benningfield, R.R. Wilborn, A.K. Johnson, R.L. Jensen, L.H. Boone