<i>Yersinia pseudotuberculosis</i> and <i>Y. enterocolitica</i> abortions in sheep and goats in California: a series of cases diagnosed at CAHFS laboratories, 2002–2023

Abortion in small ruminants poses a significant economic threat and can have zoonotic risk. Although the association between yersiniosis and reproductive complications is known, systematic studies and case series on abortion in sheep and goats are scarce. Here we describe epidemiologic and pathologic findings in 34 cases of <i>Yersinia pseudotuberculosis</i>- and <i>Y. enterocolitica</i>-associated abortions in sheep and goats, contributing to the understanding of these zoonotic diseases in California. We conducted a 22-y retrospective study to examine microbiologic and pathologic findings in abortion submissions, as well as the geographic and seasonal distribution of the analyzed cases. Yersiniosis-induced abortion was diagnosed in 22 goats and 12 sheep, with all abortions occurring in the last third of gestation. Samples from lung, liver, placenta, and abomasal contents were submitted for aerobic culture; the highest recovery of <i>Yersinia</i> spp. was from abomasal contents. Microscopically, there was severe necrotizing and suppurative inflammation in the lung, liver, spleen, kidney, and, when present, the placenta, with intralesional bacterial colonies. All cases were received from northern and central California in the winter and spring. Our study provides epidemiologic and pathologic features of <i>Yersinia</i> spp.-induced abortions in small ruminants and provides critical data to pave the way for future research, surveillance, and preventive strategies.