Eye problems are a common complaint among users of various strains of BALB/c mice. Two major strains in our production colony, the BALB/cJ (000651) and BALB/cByJ (001026), are both affected. Eyelids become mildly swollen with crust formation in the medial canthus. These crusts cover ulcers that are primarily located on the middle of the lower eyelids, although both eyelids may become involved. In addition, swelling may occur above and around the eye due to abscess formation. Abscesses may extend between the skin and cranial bones in any direction and involve the orbit late in the disease.
Microscopically, a common finding is ulceration of the eyelid at the junction of the haired skin and conjunctiva, directly over the meibomian gland. A fibrinopurulent exudate covers the ulcer. Periorbital abscesses develop in some cases, usually without palpebral ulceration.
Cultures of conjunctiva and abscesses consistently yield Pasteurella pneumotropica. However, this organism is also commonly isolated from unaffected eyes in these mice. In some preliminary studies, application of Pasteurella to unaffected eyes of SPF mice failed to induce any of the described lesions, even though the organism could be recovered. These results suggest that Pasteurella is an opportunist of questionable, if any, pathogenicity for ocular lesions.
Ulcerative blepharitis and conjunctivitis are occasionally diagnosed in the 129X1/SvJ (000691), but such lesions are rarely observed in other strains of mice maintained in production colonies at The Jackson Laboratory. These phenotypes appear to be characteristics of the BALB/c strains. Detailed studies are needed to define the pathogenesis and etiology of this common lesion.