HORSES

From the horses’ mouth – equine oral lesions from AHL pathology records 

Murray Hazlett, Josepha DeLay

Pathology diagnostic records from the AHL were searched from 1998 to May of 2018 for diagnoses of oral lesions in horses. Fifty-three cases were identified; 23 were identified as inflammatory, 21 as hyperplastic of neoplastic disease, 7 as trauma (dental attrition, bit trauma, tongue lacerations), and 2 as congenital anomalies (cleft palate).

Inflammatory disease usually involved ulceration and was often nonspecific (9 cases) or regarded as an incidental lesion in 3 cases (salmonellosis, hepatitis, colitis). Foreign-body material identified within the inflammatory response was suspected as the cause in 8 cases. Two cases were suspected as virally induced, one with equine cytomegalovirus isolated from tissue and from blood, and another suspicious because of histologic changes seen for a pox virus.

Ameloblastoma or ameloblastic fibroma was the most common dental tumor identified in 22 cases of hyperplastic or neoplastic disease (Table 1). Diagnoses were frequently qualified as “probable” because these tumors are rare and can be quite complex and inflamed. Odontomas (Fig. 1A) in domestic animals occur most frequently in horses, followed by dogs. Ameloblastomas (Fig. 1B) or ameloblastic fibromas were the most commonly diagnosed tumor of odontogenic epithelium (5 cases), and age was available in 4 of these horses, ranging from 3 to 22 y (mean = 12.5 y).  AHL

Figure 1. A. A compound odontoma in a horse, with arrows showing enamel (attempts at tooth production; arrows).

B. An ameloblastoma in a 12-y-old Standardbred showing typical palisading epithelium (arrow).