Caseous lymphadenitis outbreak in a small ruminant herd

Caseous lymphadenitis (CLA) is a chronic disease caused by the bacterium Corynebacterium pseudotuberculosis that affects small ruminants worldwide.

The objective of this case report is to describe an outbreak of CLA that occurred at the California State Polytechnic University, Pomona, in the summer of 2019 and the management strategies employed therein to contain the spread.

After careful physical screening, blood serum samples from the entire herd (n = 218 sheep, n = 32 goats) were tested using the synergistic hemolysis inhibition test to reveal antibodies present.

Animals with titer counts above 1:64 and/or containing CLA lesions were isolated and culled (n = 33 sheep,n = 4 goats) within 2 weeks of testing. Female sheep (n = 160) had higher titer counts and were culled at a much higher rate than male sheep (n = 58) (20% vs. 1.72%), whereas male goats (n = 9) more often had high titer counts and were culled as opposed to female goats (n = 23) (33.33% vs. 4.35%).

Vaccines were administered to the remainder of the herd following culling. Additional management strategies were employed, the outcome of which was a zero recurrence through August 2021.