Leptospirosis in Wild Mice: An Ongoing Concern for the Azorean Islands

Abstract

Background: Leptospirosis is a worldwide zoonotic infectious disease that affects Human and animals worldwide with increased risk in regions with temperate climates. Such is the case of the Azorean islands (a Portuguese archipelago with 9 islands) where this disease is considered endemic. Rodents of these islands have been considered the reservoir species for Leptospira and regulating measurements have been previously developed to control and prevent this disease in the archipelago. This study aims to determine a more recent infection rate of leptospirosis in the house-mouse (Mus musculus). Methodology & Findings: This retrospective study covering a period of 8 years (2011 to 2018), was performed by live capturing Mus musculus in 6 locations of S. Miguel Island (the most populated island of the archipelago). After euthanasia and necropsy of the mice, kidneys were surgically removed and processed in standard histological routine, and slides were stained with modified Warthin-Starry silver stain for spirochetes and scanned for the presence of Leptospires. It was possible to determine that from the 133 wild mice captured, 89 were positive for leptospirosis, representing a 66.91% infection rate. Conclusion: This study reveals that leptospirosis still represents an increased risk to Human lives and an uncalculated economical loss to the dairy farms of the Azorean islands.