Clinico-Pathological Manifestations of Experimental Infection of Albino Rats (Rattus norvegicus) with Leptospira interrogans

Abstract

Background & Aims: Leptospirosis is a zoonotic infection that may be associated with haematological, biochemical and multi-organ pathological changes. This study evaluated the clinico-pathological manifestations of experimental Leptospira interrogans serovar Canicola infection in albino rats (Rattus norvegicus). Study Design: A controlled experimental animal trial with two equal groups (Control versus Infected; n = 6 per group). Place and Duration of Study: Department of Veterinary Pathology, Faculty of Veterinary Medicine, University of Jos, and National Veterinary Research Institute (NVRI), Vom, Nigeria, between January and June 2023. Methodology: Twelve healthy adult albino rats (6 males and 6 females) were randomised into the Control (500 µL sterile PBS i.p.) and the Infected (1.5 × 10⁸ cells L. interrogans serovar Canicola in 500 µL PBS i.p.) groups. Animals were monitored daily for rectal temperature and body mass. On day 14 post-inoculation, blood samples were collected under deep pentobarbital anaesthesia for automated haematology and serum biochemistry (ALT, AST, Total Protein, Albumin, Globulin, Bilirubin, Urea). Visceral organs (kidneys, lungs, liver, heart, and intestines) were processed for routine H&E histopathology. Results: Infection induced significant pyrexia (37.21 ± 0.42 °C vs 35.13 ± 0.32 °C; P = .005) and body weight loss (95.28 ± 2.29 g vs 120.58 ± 1.31 g; P = .004; -20.98% drop). Haematology demonstrated normocytic normochromic anaemia (PCV: 33.33 ± 1.03% vs 39.17 ± 2.48%; P = .001; Hb: 9.63 ± 1.06 g/dL vs 12.12 ± 0.62 g/dL; P = .001) and acute neutrophilia (49.67 ± 4.80% vs 34.17 ± 3.49%; P = .001). Serum biochemical analysis revealed a mild elevation in Alanine Aminotransferase (ALT: 58.57 ± 5.62 IU/L vs 49.27 ± 3.54 IU/L; P = .006), and Aspartate Aminotransferase (AST: 89.35 ± 9.74 IU/L vs 82.98 ± 7.62 IU/L; P = .236) These elevations may not be considered as statistically significant. Histopathological evaluation revealed microscopic lesions consistent with acute tubular necrosis (ATN) in the kidneys, pulmonary vascular congestion and interalveolar septal haemorrhage, centrilobular hepatocyte degeneration, myocardial hyaline necrosis, and sloughing of the intestinal villi. Conclusion: Experimental L. interrogans infection in albino rats causes acute pyrexia, somatic wasting, anaemia, neutrophilia, and multi-organ tissue injury. The findings provide an experimental model of acute spirochaetaemia and microvascular injury while adhering to ARRIVE 2.0 reporting standards.