# Ocular Involvement as a Key Marker of Systemic Disease in Dogs Naturally Infected with Leishmania infantum: Clinical, Laboratory, and Histopathological Insights

## TL;DR

This study shows that eye problems in dogs infected with Leishmania infantum are common and linked to broader systemic disease, highlighting the need for eye exams in managing the condition.

## Contribution

The study provides new clinical, laboratory, and histopathological evidence linking ocular involvement to systemic disease in dogs with Leishmania infantum.

## Key findings

- Ocular alterations were observed in 80% of infected dogs, often bilateral and associated with multiple lesions.
- Dogs with eye involvement showed higher leukocyte counts and increased AST levels, indicating systemic inflammation.
- Histopathology revealed plasmacytic inflammation and parasites in ocular tissues, suggesting immune and parasite-driven mechanisms.

## Abstract

Canine visceral leishmaniasis (CVL), caused by Leishmania infantum, is a multisystemic disease in which ocular involvement is frequent but often underestimated. This study aimed to comprehensively evaluate the clinical, ophthalmological, parasitological, hematological, biochemical, and histopathological alterations in dogs naturally infected with L. infantum from an endemic area of northeastern Brazil, with special emphasis on the relationship between ocular manifestations and systemic disease. Twenty-five symptomatic dogs were evaluated through clinical and ophthalmological examinations, parasitological culture, PCR, laboratory analyses, and histopathology of ocular and periocular tissues. Ocular alterations were observed in 80% of the animals, predominantly bilateral and frequently associated with multiple concurrent lesions, including ocular discharge, conjunctivitis, blepharitis, uveitis, and corneal opacity. Functional ophthalmological tests revealed keratoconjunctivitis sicca and corneal ulcers in a substantial proportion of dogs. Hematological abnormalities were highly prevalent, particularly anemia and thrombocytopenia. Comparative analysis demonstrated that dogs with ocular involvement exhibited significantly higher leukocyte counts and segmented neutrophils, as well as increased AST levels, indicating an enhanced systemic inflammatory response. Histopathological examination revealed intense plasmacytic inflammatory infiltrates and the presence of amastigote forms in ocular and periocular tissues, indicating that both immune-mediated and parasite-driven mechanisms could be involved in disease pathogenesis. Collectively, these findings underscore ocular involvement as a clinically relevant manifestation of CVL and reinforce the importance of routine ophthalmological evaluation in clinical management.