Histopathological Findings of Foot-Rot Disease Which Causes Deaths in a Sheep Flock

Abstract

Background: Foot-rot is a contagious bacterial infection of the feet of sheep that causes lameness. This infection leads to major economic losses in wool, meat, and dairy industries throughout the world. Pathogenesis of foot-rot can be described as the damage of the interdigital skin, invasion of fecal bacterium Fusobacterium necrophorum, and finally the involvement of Dichelobacter nodosus in the infection. In the worst cases, the disease becomes widespread, and systemic bacterial infections may occur. The present study aims to describe macroscopic and histopathological findings of foot-rot lesions formed in the foot, heart, liver, and lungs to draw attention to these aspects of the disease. Case: The material of the study consisted of a 3-year-old sheep. The investigation was composed of the disease history; post-mortem examination; and histopathological analysis of lung, liver, heart, and foot lesions. At the anamnesis, it was reported that the diseased animal had lameness and weakness with other clinical symptoms, and approximately 10 infected sheep had died within a 1-week period. At necropsy, malodorous ulcerative lesions between the nails; focal-disseminated foci in the liver, lung, and heart; yellowish matte thickening in the heart valves; and hydropericardium were detected. After necropsy, tissue samples taken from the skin, lungs, spleen, kidneys, and liver were fixed in a 10% buffered formalin solution, paraffin embedded, sectioned, and stained with hematoxylin and eosin. Giemsa staining was done to detect the agents in the tissues. The slides were examined and photographed using a light microscope. Histopathological examination revealed that ulcerations between the nails were lesions shaped as the result of the foot rot disease. The focal-disseminated lesions in the internal organs were the foci of metastatic-embolic inflammation originating from the lesions between the nails. Rod-shaped bacteria were detected in foot, liver, and lung tissues by Giemsa staining. Discussion: Foot-rot has important economic and welfare impacts. A number of researches on the characterization of agents, regional incidence, pathogenesis, and macroscopic characterization and classification of lesions in the nail have been carried out on footrot disease. In the present case, the disease became systemic and numerous sheep died. Systemic infections are characterized embolic-metastatic inflammations formed in major vital organs such as the liver, lungs, brain, heart, and kidneys as the result of the vasculitis formed in the veins in the inflamed region, where the agents are spread by the bloodstream. Histopathologically, granulomatous foci were seen in the liver and lungs. In the middle of these foci were collapsed leukocytes and agents, and the surrounding area was composed of Langhans, foreign body giant cells, and mononuclear cells. Treatment with systemic infections is quite difficult. The disease can be treated, but the cost of treatment and care is very high. For this reason, foot-rot disease is among the most expensive sheep diseases requiring costly treatment. Because we believe foot-rot disease not only causes lameness but also leads to high mortality rates in sheep flocks, we presented the pathological findings to draw attention to these aspects of the disease. As far as we can investigate, no case reports have presented both macroscopic and microscopic findings of the disease that have formed in nails and internal organs. © 2017 Universidade Federal do Rio Grande do Sul. All rights reserved.