MICROBIOLOGIC, RADIOGRAPHIC, AND ANATOMIC STUDY OF THE NASOLACRIMAL DUCT APPARATUS IN THE RABBIT (ORYCTOLAGUS-CUNICULUS)

This study was motivated by the sporadic observation of epiphora in tw o male rabbits. The epiphora was unilateral and not associated with co njunctivitis or Pasteurella infection. To characterize the cause of ep iphora, we studied 15 specific-pathogen-free New Zealand White rabbits . This study group was composed of the two affected males, four unaffe cted males, and nine unaffected females. Clinical evaluation consisted of bacterial culture of conjunctival specimens, examination of conjun ctival scrapings for chlamydial inclusions, culture and cytologic exam ination of specimens from the nasolacrimal duct, plain and contrast ra diography, latex casting, histologic examination, and the Schirmer tea r test. Important differences found in the rabbits with epiphora inclu ded an opalescent, gritty, nasolacrimal duct flush fluid and marked un ilateral dilatation of the duct proximal to a dorsal flexure at the ca udal limit of the incisor tooth root. The flush solution from one affe cted rabbit cleared with ether, suggesting the presence of triglycerid es or cholesterol. The organisms most commonly isolated from the conju nctiva were Moraxella sp., Oligella urethralis, Staphylococcus aureus, coagulase-negative Staphylococcus sp., and Streptococcus viridans. Th e organisms most commonly isolated from the nasolacrimal duct flush fl uid were Moraxella sp., S. viridans, and Neisseria sp. Culture of the nasolacrimal duct hush fluid yielded microorganisms more consistently than did culture of the conjunctival specimens. All microorganisms iso lated from affected rabbits also were isolated from unaffected rabbits . There was no apparent contribution of microorganisms to the developm ent of epiphora, and Schirmer tear test results for affected animals w ere within the range seen in unaffected animals. Occlusion of the naso lacrimal duct was presumed to be attributable to fat droplets. This st udy augments the existing literature and represents the first report o f anomalous nasolacrimal duct anatomic features in the rabbit.