The Relevance of Caseous Lymphadenitis as a Cause of Culling in Adult Sheep

SIMPLE SUMMARY: Caseous lymphadenitis is a widespread disease, which has been noticed in most sheep farming countries, causing important economic losses. This disease produces emaciation and weakness in the animals and has to be considered in the differential diagnosis of the so-called ‘’thin ewe syndrome’’, especially when sheep are affected by the visceral presentation of the disease. The present study analysed the prevalence of the disease in the Ebro valley area in Spain and its implication as a cause of culling in adult sheep. ABSTRACT: Four hundred and ninety-eight culled sheep received at the Ruminant Clinical Service of the Veterinary Faculty of Zaragoza, Spain, were examined in life and after humanitarian sacrifice in order to reach the final diagnosis of the cause of culling and to evaluate the presence of caseous lymphadenitis (CLA) lesions. One hundred and forty-seven of the 498 studied animals (29.52%) showed CLA compatible lesions that were subsequently confirmed by Corynebacterium pseudotuberculosis isolation. One hundred and seven of the 147 CLA affected animals presenting the visceral clinical form of the disease (72.79%), while only 32 animals were affected by the superficial form (21.77%). In addition, eight animals were found to be affected in both the visceral and the superficial presentations (5.44%). Eighty-four of the 147 CLA-affected animals (57.14%) did not show any concurrent disease, considering, in this case, CLA the main cause of culling (84/498: 16.87%). In the superficial presentation, the retropharyngeal lymph node, as a sole lesion, was the most frequently affected (13/32: 40.63%). Further, in the visceral form of the disease, 85.06% of the affected animals had the lesions located in the respiratory system (91/107: 85.06%). CLA was revealed as an important cause of culling in sheep production.