Yersinia pseudotuberculosis abortions in small ruminants

Amanda Mansz

Animal Health Laboratory, University of Guelph, Guelph, ON

AHL Newsletter 2023;27(2):10.

A postmortem submission of two 2-3 week pre-term Saanen (meat) caprine fetuses from a flock with several recent abortions was received at the AHL in January 2023.   At postmortem examination, both fetuses had slightly enlarged livers with subcapsular congestion and hemorrhage with random multifocal pin-point foci of necrosis (Fig. 1A).  One of two fetuses had a moderate amount of clear abdominal fluid, edema of the abdominal mesentery, diaphragm and subcutaneous tissues of the ventral abdomen/thorax.   Renal and pulmonary hemorrhages were noted, and the distal small intestine was dark red to purple on both the serosal and mucosal surfaces (Fig. 1A).  Microscopic lesions of embolic hepatic and splenic necrosis, suppurative gastroenteritis and suppurative pneumonia were compatible with fetal sepsis (Fig. 1B).  Subsequently, in March 2023 a Rideau-cross ovine fetus and placenta was received for postmortem.  Although visible gross lesions of the fetus were minimal, placental lesions were appreciable and included mild intercotyledonary thickening and opacity with subtle necrosis of cotyledons.  Microscopic lesions were also compatible with fetal sepsis, consisting of suppurative pneumonia, epicarditis and abomasitis.  There was necrosuppurative placentitis with vascular necrosis and visible rod-shaped bacteria.  Bacterial culture of the lung and abomasal content from the caprine fetuses, and of the placenta, lung and abomasal content from the ovine fetus, all grew large numbers of Yersinia pseudotuberculosis.

Yersinia pseudotuberculosis is a Gram-negative aerobic or facultative anaerobic rod-shaped bacterium implicated in causing various diseases in a wide range of species, and is also a zoonotic food-borne pathogen.  Y. pseudotuberculosis is found worldwide and can be an inhabitant of the intestinal tract of asymptomatic birds, rodents, livestock, primates, and laboratory animals.  Transmission most commonly occurs by the fecal-oral route following ingestion of contaminated food or water.  The bacteria can survive long periods of time in the environment, even at temperature as low as 4 degrees Celsius.

In a 23-year retrospective study conducted in North America, Y. pseudotuberculosis–associated disease was diagnosed in 42 goats from 21 counties, with a strong seasonality in winter and spring.  The most frequently diagnosed syndromes in ruminants include: enterotyphlocolitis, lymphadenitis, abortion and neonatal death, mastitis, orchitis, septicemia, and ocular disease.  The pathogenesis of abortion is thought to follow invasion of the intestinal epithelium of the dam, transient bacteremia, and localization in the maternal caruncle, followed by passage to the chorioallantois and fetus.  Most published cases of Y. pseudotuberculosis in small ruminants are of individual animals or small groups rather than large outbreaks.  This organism is an important documented cause of food-borne illness in humans, and outbreaks have occurred following ingestion of contaminated milk, meat, fresh vegetables, and water. AHL

Figure 1.  Aborted goat fetus with Y. pseudotuberculosis sepsis A.  Blotchy hepatic subcapsular congestion and hemorrhage with multiple pin-point white foci of necrosis (white arrows).  Dark red to purple distal small intestine covered with edematous mesentery (yellow arrow) B.  Rafts of neutrophils and necrotic cellular debris line the flattened and eroded jejunal lumen and fill crypts.  H&E stain.

References

1. Giannitti F, et al. Yersinia pseudotuberculosis infections in goats and other animals diagnosed at the California Animal Health and Food Safety Laboratory System: 1990-2012. J Vet Diagn Invest 2014;26:88-95.

2. Schlafer DH, Foster RA. Female Genital System. In: Jubb, Kennedy, and Palmer's Pathology of Domestic Animals, 6th ed. Maxie MG, ed. Elsevier, 2016;vol 3:413.