Longitudinal Follow-Up of Clinical Superficial Ovine Caseous Lymphadenitis.

Caseous lymphadenitis is an infectious disease that has a significant economic impact on sheep breeding. The objectives of this study were to evaluate the effect of season, animals' age, sex, body score and shearing on the clinical incidence of caseous lymphadenitis, relapses and abscess location in sheep from Settat province, Morocco. In this longitudinal study, 274 clinically healthy sheep were recruited in six flocks among 1451 inspected sheep and followed during 12 months to cover four seasons. The animals involved in this study were assigned to different age categories at continuous recruitment from February to July 2021 (lambs younger than 6 months, young sheep between 6 and 24 months and old sheep more than 24 months) and to sex categories. Selected animals were clinically examined every 2 months to detect superficial abscesses by palpation of superficial lymph nodes. Information about the number of abscesses and their locations was recorded and analyzed in multivariable statistical models. The results showed that 185/274 (67.5%) of the monitored animals developed superficial CL abscesses. The risk ratio (RR) of superficial CL was significantly higher between April and September compared to between January and March (RR~4.4;