Frequency of caseous lymphadenitis (CLA) in sheep slaughtered in an abattoir in Tabriz: comparison of bacterial culture and pathological study

Abstract

From January to February 2008, 468 sheep carcasses (335 male and 133 female) in a Khosroshahr (suburb of Tabriz, East Azerbaijan province, Iran) abattoir were randomly selected for inspection. The aim of the study was to estimate the frequency of caseous lymphadenitis (CLA) in sheep and to compare the results of bacterial cultures and histopathology of suspected cases. The mean age of the population was 2.5 years. One hundred ninety-seven cases containing 153 (77.7%) males and 44 (22.3%) females had prominent enlargement of one of the lymph nodes (i.e., prescapular, prefemoral, inguinal, supramammary, or midiastinal); these were removed with the surrounding tissue for further evaluation. For confirmed diagnosis of CLA, samples were sent for microbiology and pathology analysis. Standard bacteriological culture methods for isolation of Corynebacterium pseudotuberculosis and tissue preparations for histopathological sections were performed. To evaluate the effect of age on the frequency of CLA, animals were categorized in four groups: under 1, 1–2, 2–3, and over 3 years of age. Based on the results, in 59 (12.60%) carcasses C. pseudotuberculosis was isolated, and in 94 (20.08%) of the cases histopathological studies revealed pathognomonic signs (lamellated exudates or onion ring) of CLA. The frequency of CLA based on bacteriological culture was 12.60% and on histopathological study 20.08%. In 37 (18.8%) of the carcasses, both bacteriological and histopathological studies confirmed CLA. The frequency of CLA following microscopic examination (20.08%) presented a more precise diagnosis compared to bacteriological culture (12.60%) and macroscopic evaluation of the lymph nodes (P < 0.05). Furthermore, there was a positive correlation rate between the bacteriological culture and histopathological study (r = 0.196, P = 0.006). The prescapular lymph node had the highest infection rate with 54 (1.70 ± 0.97) and supramammary lymph node had the lowest with two (0.07 ± 0.41) (P < 0.05). There was an increase in CLA detection with increasing age (P < 0.05), the mean age of animals with a positive CLA test were 2.92 years and in the oldest age group 31 (47%) cases had the highest infection.

Clinico-Pathological and Bacteriological Studies on Caseous Lymphadenitis in Small Ruminants

“…Abscess formation in cut sections of lungs and liver due to C. pseudotuberculosis in alpaca has been reported (Braga et al, 2006;Fontaine and Baird, 2007). Previous studies have disclosed that presence of small tubercles packed with caseous material in lungs, liver, internal lymph nodes and mesenteric lymph nodes are the characteristic features of visceral forms of caseous lymphadenitis caused due to C. pseudotuberculosis (Yeruham et al, 2003;Zavoshti et al, 2012;Chikhaoui and Khoudja, 2013). Different studies have also reported similar pathological lesions in infected animals (Pratt et al, 2005;Quino de Sa et al, 2013;Chikhaoui and Khoudja, 2013).…”

“…Initially these lymph nodes are filled with serous fluid which later on is converted to pus filled tubercles. The disease also causes lesions in other visceral organs including liver, lungs and spleen (Zavoshti et al, 2012). C. pseudotuberculosis biovar ovis induces diffused swellings in brisket regions, skin of fore limbs and hind quarter in exposed animals (Moussa et al, 2016).…”

“…C. pseudotuberculosis infection causes huge losses particularly in different agro-ecological areas including tropical, subtropical, arid and semi-arid areas across Asia, Africa, South and Central America (Aquino de Sa et al, 2013). High prevalence of C. pseudotuberculosis infection has been reported in different meat producing countries of the world such as United States, New Zealand, India, South Africa, Canada, Australia, Brazil, China and Iran (Dorella et al, 2009;Kumar et al, 2012;Zavoshti et al, 2012;Alvarezet al, 2017). C. pseudotuberculosis also causes an acute skin infection in buffaloes resulting poor milk production (Oedematus skin disease) in buffaloes (Selim, 2001;Mousa et al, 2016).…”

Morel’s Disease and Caseous Lymphadenitis: a Literature Review with Special Reference to Saudi Arabia

“…They are non-fatal chronic or subclinical with high morbidity rate and frequent relapses [4,9,13]. MD is mainly encountered in young animals within the first 4-10 months of life [32], while CLA is mainly in adult animals and is found increasing with age [33]. Unlike CLA, MD was found associated with fattening; incidence was found to be higher in feedlot areas (62.5%) compared to natural grazing areas (5.8%) [34].…”

Seroprevalence of caseous lymphadenitis in Kangal Akkaraman sheep

“…Similarly, the CLA prevalence in sheep was found as 42.4% in a study conducted in the western United States (10), and 12.6% from bacteriological analysis and 20.08% from histopathological analysis in Tabriz (Iran). While the frequencies of CLA observation in sheep and goats were 23.33% and 11.04%, respectively, according to clinical examination, these frequencies were reduced by 22.10% and 7.77% in sheep and goats, respectively, if the agent was determined through bacteriological methods (11). CLA positivity in sheep was identified as 71% in a study using an indirect ELISA method in Brazil (9).…”