E casseliflavus is a particular strain of enterococcus commonly found in the gastrointestinal tract of livestock such as cattle and horses.1 It has rarely been associated with human infection. There have been a few cases involving polymicrobacterial bacteremia with biliary tract disease in humans.2 A PubMed search of the literature from 1951 to 2008 revealed no reports of E casseliflavus and eye infection. In this case, the etiology of the E casseliflavus endophthalmitis is not clear. The blood culture results were negative and the patient was afebrile, making endogenous endophthalmitis less likely. The horse tail injury may have introduced the pathogen. E casseliflavus is the most common strain found in fresh and dry horse manure,1 the likely source of infection. However, the mechanism is unclear as there was no entry site for the bacteria (ie, no evidence of a ruptured globe, corneal ulcer, or corneal perforation). The conjunctiva was chemotic, but on surgical exploration there was no evidence of a gross perforation. The horse tail injury might have caused a self-sealing microperforation through the cornea or the conjunctiva, which may explain how the bacterial strain entered the eye. The patient did have abrasions around his face from the horse tail whip, suggesting that the tail could have hit the eye as well. Animal tail whip injuries have been reported to cause traumatic subconjunctival crystalline lens3 and intraocular penetration with the animal hair.4 Ophthalmologists must be aware that tail whip injuries can have serious visual consequences.