Prevalence and molecular investigation of caseous lymphadenitis among the slaughtered sheep at Duhok Abattoirs; experimental infection with Corynebacterium pseudotuberculosis in rabbits

Nawzat Issa,Hivi Hameed,Rezheen Fatah,Kareem Kareem,Bahroz Ahmed,Muhammad Hussen,Zirak Najeeb,Handren Hamadamin,Zanan Taha

doi:10.33899/ijvs.2020.126772.1377

Abstract

Caseous lymphadenitis is a chronic infection caused by Corynebacterium pseudotuberculosis that affects the lymphatic system, resulting in abscesses in the lymph nodes and internal organs. This study was conducted to determine the prevalence rate of caseous lymphadenitis among slaughtered sheep in Duhok abattoirs, Duhok, Iraq and to investigate to what extend rabbits can develop caseous lymphadenitis just like that in sheep. A total of 1052 carcasses of sheep were randomly selected (939 males and 113 females) and carefully inspected for detection any suspected caseous lymph adenitis. The isolated Corynebacterium pseudotuberculosis from lymph nodes of sheep carcasses were identified by PCR before used in in vivo infection in rabbits. Data revealed that the prevalence rate of caseous lymphadenitis was at 1.9% among the slaughtered sheep and the prevalence rates were higher in females and older ages than that of males and younger ages, respectively. Experimentally infected rabbits developed various clinical signs were ranging from in inappetence to sudden death, mainly during first week of infection. Histopathologically, the infected rabbits developed caseous lymphadenitis and pyogranuloma after a time point of 10 days post-infection. Liver, spleen and lymph nodes of infected rabbits showed caseo-necrotic foci with multiple micro-granulomas with presence of thick pyogenic membrane infiltrated with leukocytic cells; these findings are strictly resemblance to that reported in sheep. The obtained preliminary data of using rabbits as an animal model is promising which will enhance a better understanding the pathogenesis of caseous lymphadenitis in animals.

Highlights

Caseous lymphadenitis (CLA) is a chronic, contagious bacterial disease caused by the bacterium Corynebacterium pseudotuberculosis (C. pseudotuberculosis)
Prevalence rate of CLA among slaughtered sheep The data found that 20 out of 1052 of inspected carcasses of sheep were infected with CLA at prevalence rate 1.9%; among the age groups, the data revealed that the prevalence rates were higher in sheep at age of three years and older than that found in sheep of younger ages
CLA of the mediastinal lymph nodes were found in variable sizes and contents, the pus was cheesy, creamy -milky to pale green in color as shown in (Figure 1)

Summary

Introduction

Caseous lymphadenitis (CLA) is a chronic, contagious bacterial disease caused by the bacterium Corynebacterium pseudotuberculosis (C. pseudotuberculosis). It is manifested clinically as abscesses of peripheral and/or internal lymph nodes and organs [1]. The pus content of the infected lymph nodes is very thick and with no smell [2]. The peripheral form presents as abscesses of single or multiple peripheral palpable lymph nodes, internal CLA typically manifests as chronic weight loss and ill thrift [3]. The disease is economically very important and it associates with great economic losses ranging from reduction within the meat and milk productions, damage of carcasses to death [6]

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