Identifying Visceral Leishmaniasis

Canine visceral leishmaniasis (VL) is caused by Leishmania infantum/chagasi, and dogs are the primary reservoir hosts. This study examined ocular signs in dogs with VL by L infantum. Dogs from an enzootic population in Barcelona were diagnosed with visceral leishmaniasis based on clinical signs and clinicopathologic findings. Diagnosis was confirmed by direct parasite identification, polymerase chain reaction, and serology. Dogs that died or were euthanized over a 4-year period were evaluated. Both globes were collected postmortem, fixed, sectioned, and stained. Immunohistochemistry or parasite identification was used to identify ocular tissues as positive for Leishmania. Perivascular lymphoplasmacytic infiltration and pyogranulomatous aggregates were identified in the subconjunctival tissue and limbus, cornea, sclera, iris, ciliary body, iridocorneal angle, choroid, and the optic nerve sheath in some of the globes. An association was established between the presence of ocular clinical signs and the presence of a characteristic granulomatous inflammatory infiltration with macrophages, lymphocytes, plasma cells, and parasites. This accounts for ocular clinical signs of leishmaniasis in canine patients.

COMMENTARY: This article discusses a diverse number of ocular tissues that exhibited granulomatous and lymphoplasmacytic inflammation with or without intralesional parasites. These varied findings are interesting as they are consistent with the differing clinical signs observed in canine leishmaniasis. The study also shows that the parasite is often intralesional, highlighting the systemic nature of this disease. The findings suggest that disseminated leishmaniasis could and should be included in the differential diagnoses for animals in enzootic areas presenting with numerous ocular disturbances.

Histopathologic features of ocular leishmaniosis in the dog. Pena MT, Naranjo C, Klauss G, et al. J COMP PATHOL 138:32-39, 2008.