SOME EPIDEMIOLOGICAL AND PREVENTIVE MEASURES FOR CASEOUS LYMPHADENITIS IN SHEEP AT QUALIN DISTRICT

Caseous Lymphadenitis (CLA) is a contagious chronic disease of small ruminants caused by a gram-positive aerobic facultative micro organism. In this study, a cross sectional study was carried out to estimate CLA prevalence among sheep population in Qualin district. Out of 315 examined sheep, 10% were showed the clinical signs of CLA. Serologically, 144 sheep were examined by ELISA which resulted in a true seroprevalence of 61% (95% CI: 53-69%). evaluation of application of Betadine on wounds and using of shearing machine as control measures for CLA in sheep flocks resulted in the decrease the prevalence of CLA from 9.3% to 2.6 % in an infected flock. In conclusion, CLA is a endemic disease in the study area at high levels of prevalence and official control measures has to be undertaken to minimize its huge economic losses. INTRODUCTION Caseous Lymphadenitis (CLA) is a contagious chronic disease of small ruminants caused by a gram-positive aerobic facultative coocobacilli; Corynebacterium pseudotuberculosis (Fontaine and Baird 2008). CLA is of significant economic concern for sheep husbandry due to reduced wool, meat and milk yield, loss of fertility, culling of affected animals, condemnation and downgrading of affected carcass at slaughter and meat inspection (Williamson 2001; Guimaraes et al. 2011). Some Epidemiological And Preventive Measures For . Dalal Y. Rizk et. , al. Kafr El-Sheikh Vet.Med.J. Vol. 1 No.1 (2003) ٢ Two forms have been described for CLA; external and internal forms. External form characterized by abscess in superficial lymph node and subcutaneous tissue. Internal form characterized by internal abscess located in the internal organs especially the lung, liver, kidney and bronchial, lumber lymph node with animal wasting: thin ewe syndrome (Ivanovic et al. 2009; Oreiby et al. 2013). Clinical signs and post-mortem of CLA have diagnostic values but the confirmation of diagnosis generally achieved by the bacterial culture, serological and nucleic acid based detection methods (Ilhan 2013). The most popular serological test for CLA is ELISA using different antigenic components including PLD (extracted from culture supernatant or in recombinant form rPLD) (Sting et al. 2012; Oreiby 2015). The sources of infection to healthy animals are abscesses discharging from ruptured external lymph nodes which contaminate the shearing and feeding equipment which are responsible for spread of the organism (O’Reilly et al. 2008). There are many risk factors for CLA spread such as; the lacking of sanitary measures (Chirino-Zarraga et al. 2006). Control of CLA has some element; using penicillin at day zero of shearing in addition to disinfection of shearing instrument and wounds greatly reduced the disease occurrence (Al-Gaabary et al. 2009). A routine palpation of the superficial lymph nodes in sheep, for detection the infected animals. And shearing equipment and supplies should be routinely cleaned and disinfected before use. (Windsor 2011). Some Epidemiological And Preventive Measures For . Dalal Y. Rizk et. , al. Kafr El-Sheikh Vet.Med.J. Vol. 1 No.1 (2003) ٣ MATERIAL AND METHODS Animals and clinical examination: A total of 315 sheep of different ages and sexs in Qualin district of Kafrelsheikh governorate were examined clinically for CLA. Out of the examined animals, 75 belonged to governmental flock and 265 animals belonged to private flocks. All animals were subjected to careful clinical examination according to (Rosenberger et al. (1979). Bacteriological examination: ASamples for bacteriology examination: Aspiration: Closed abscessaited superficial lymphnods were aseptically aspirated using sterile syringe, and after disinfection of the skin by Betadine. Swabbing: pened abscessaited superficial lymphnodes were deeply swabbed using sterile cotton swabs. Pus sample were transferred to laboratory on ice for bacterial isolation and identification. BIsolation and identification: Pus samples were cultured on 10% sheep blood agar and brain heart infusion agar media then incubated aerobically-at 37 ° C enriched with 5% co2 for 48 hours according to the method described by (Bailey and scott1990). The resultant colonies were examined for consistency , colour, type of hemolysis and their ability to be pushed across the agar surface (Selim, 2001). Bacterial films were prepared, fixed and stained by Gram's stain and examined microscopically. Stain reaction, shape and arrangement of the bacterial cells and the presence of were investigated. The confirmation of identification was done using PCR for the isolated colonies (unpublished work). Some Epidemiological And Preventive Measures For . Dalal Y. Rizk et. , al. Kafr El-Sheikh Vet.Med.J. Vol. 1 No.1 (2003) ٤ Serological examination: Blood samples were collected from 149 examined animals in 10 cm syringe and were sent to lab. Serum were separated by centrifugation and kept in -20 ° C till used for ELISA according to (Menzies et al. (2004) with some modifications. The antigen used in this serological test is the exotoxin prepared from local strain of C. pseudotubercullosis by the same authors of this article (unpublished data). Statistical analysis: The prevalence of clinical CLA among examined animals was estimated as followings: P = (Number of animals with superficial abscesses/Number of examined animals) x 100 Thrusfield M (2007). While the apperent seroprevalence of CLA was estimated as following: AP = (Number of animals seropositive to CLA using ELISA/Number of examined animals against CLA using ELISA) x 100 Thrusfield M (2007) The true seroprevalence of CLA was estimated as following: TP= AP+Sp-1/Se+Sp-1 Thrusfield M (2007). Where TP is the true seroprevalence, Se is the sensitivity of ELISA (81%) and Sp is the specificity of ELISA (98%) (Sting, 2012) The confidence interval for the TP was estimated as following:   n p p Z p CI    1 * * Thrusfield M (2007) Some Epidemiological And Preventive Measures For . Dalal Y. Rizk et. , al. Kafr El-Sheikh Vet.Med.J. Vol. 1 No.1 (2003) ٥ Preventive measures: The governmental flock was subjected to wound disinfection using betadine solution in all wounds produced during shearing. Around 35 animals were injected with Penicillin G Benzathin at the searing time. The prevalence of CLA was 8% before application of this preventive measures. The flock was followed up for 1 year. Evaluation of the efficacy of the preventive measures was done on the basis of the appearance of the new cases within a year post management and estimating the disease prevalence. Using of shearing machine and shearing scissors to assess the role of shearing machine in sheep flocks in decreasing the number of wounds during shearing process in sheep flocks. All statistical analysis were carried out using chi square test and fisher's test on SPSS V 19.