JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

August 2023

P-B11 (NP)

 

Signalment (JPC #2015661): Ovine fetus

 

HISTORY: One of two crossbred ovine fetuses that were aborted approximately 3-4 weeks prior to the expected date of parturition

 

HISTOPATHOLOGIC DESCRIPTION: Lung: Affecting approximately 25% of the section and effacing pulmonary architecture are multifocal, random foci of necrosuppurative inflammation composed of a central area of eosinophilic cellular and karyorrhectic debris (lytic necrosis) and large colonies of 1 x 2 µm coccobacilli surrounded by high numbers of viable and degenerate neutrophils and fewer macrophages and lymphocytes. Multifocally, bacterial colonies are present within alveolar capillaries. Diffusely, the remaining alveolar spaces, alveolar septa, vasculature, and bronchioles contain scattered previously described inflammatory cells; eosinophilic, fibrillar material (fibrin); edema; few erythrocytes (hemorrhage); necrotic cellular debris; and rarely globular yellow material (meconium). The perivascular interstitium is expanded by widely dilated lymphatics and amorphic, homogenous, eosinophilic material (edema). Diffusely, there is atelectasis and congestion.

 

MORPHOLOGIC DIAGNOSIS: Lung: Pneumonia, embolic, necrosuppurative, subacute, severe, with meconium and numerous large colonies of coccobacilli, crossbred sheep, ovine

 

ETIOLOGIC DIAGNOSIS: Pulmonary yersiniosis

 

CAUSE: Yersinia pseudotuberculosis

 

GENERAL DISCUSSION:  

• Pathogenic species of the genus Yersinia include Y. pestis (causative agent of plague), Y. pseudotuberculosis, and Y. enterocolitica; the latter two cause indistinguishable enterocolitis, mesenteric lymphadenitis, and, less often, conjunctivitis, pneumonia, hepatitis, abortion, neonatal death, mastitis, and epididymitis-orchitis 
• Results in epidemics in wild rodents and birds with sporadic outbreaks in domestic animals (sheep, cattle, goats, deer, pigs, and rarely carnivores and others)
• It is widely distributed in soil, water, and food (milk and meat products, vegetables); can survive and replicate in the soil and in aquatic environments outside of host for months to years 
• Zoonotic, facultative anaerobic, oxidase-negative, gram negative, coccobacillus 

 

PATHOGENESIS:

• Shed in the feces of asymptomatic herd and flock animals and wild rodents and birds; persists in the environment; outbreaks often occur secondary to stress, especially during cold weather  
• Ingestion > invades through intestinal epithelium or M cells > enters lamina propria and/or submucosal lymphoid tissue > neutrophil-mediated tissue destruction centered on Peyer’s patches (microabscesses) > dissemination via lymphatics and portal system to mesenteric lymph nodes, liver, and elsewhere 
• Virulence related to plasmid pYV and other proteins such as invasin, which binds beta-1 integrins to facilitate translocation across the terminal ileum and induces chemokine (IL-8) production, and YadA and Ail, which protect the bacteria from phagocytosis within Peyer’s patches and enables propagation to mesenteric lymph nodes and other tissues 
• Primarily an extracellular bacteria, but some reside intracellularly (facultative intracellular organism), stimulating giant cell formation to wall off infection (hence pseudotuberculosis) and T-cell mediated immunity to clear the infection 
• Abortion can occur after localization of bacteria in maternal caruncle, followed by passage to the chorioallantois and the fetus

 

TYPICAL CLINICAL FINDINGS:

• Latent infections are common; asymptomatic carriers can break with disease during periods of stress (cold and wet weather, overcrowding, capture, etc.), resulting in herd or flock outbreaks
• Mild diarrhea with low mortality to severe, hemorrhagic diarrhea and sepsis
• Abortion (esp sheep, goats, and cattle) 

 

TYPICAL GROSS FINDINGS:

• Triad of lesions: Fibrinohemorrhagic enterocolitis (centered over Peyer’s patches), multifocal hepatic and splenic necrosis or abscesses, and mesenteric lymphadenopathy 
• Occasionally, similar lesions in lungs, kidneys, and bone marrow
• Abortion: Suppurative placentitis, mostly confined to the cotyledons with pericotyledonary fibrin, and fetal miliary hepatic necrosis 

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Necrosis, microabscesses or pyogranulomas with large colonies of gram-negative coccobacilli within the distal half of the small intestine and large intestine, mesenteric lymph nodes, liver, spleen, and other organs 
  1. Bacteria typically coccobacilli, but aberrant morphologies have been described (large globular bodies, filamentous) 
• Abortion: Placental cotyledonary villar necrosis, mixed inflammatory infiltrate, and fibrinoid vascular necrosis; Fetal multifocal necrosis, edema, and inflammation within the liver, myocardium, lymph nodes, lung, etc. 

 

ADDITIONAL DIAGNOSTIC TESTS:

• Cold enrichment and culture at temperatures below 37ºC
• PCR

 

DIFFERENTIAL DIAGNOSIS:

Bacteria that appear histologically as large colonies: 

• Yersinia enterocolitica and pestis: Differentiate by culture and PCR
• Actinomyces sp. gram (+)
• Actinobacillus sp. gram (-)
• Corynebacterium sp. gram (+)
• Staphylococcus sp. gram (+)
• Streptococcus sp. gram (+)
• Trueperella pyogenes gram (+)

 

COMPARATIVE PATHOLOGY:  

• Hamsters: Necrotic caseous nodules in intestine, mesenteric lymph nodes, liver, spleen, and lungs
• Guinea pigs: Acute- miliary cream-colored nodules in intestinal wall, enteritis, mucosal ulceration (esp. terminal ileum and cecum); subacute to chronic- miliary to caseous lesions in mesenteric lymph nodes, spleen, liver, and lung
• Rabbits: Acute to chronic granulomatous infections with focal caseous necrosis of liver, spleen, cecum, lymph nodes, and reproductive tract
• Birds: Common in passerines, ramphastids, turacos, and doves in Europe, but rare within the United States (including poultry and pet birds); toucans highly susceptible; acute septicemia with necrosis and miliary abscesses within the liver, spleen, and lungs, followed by chronic caseous nodules resembling avian tuberculosis
• NHP: Reported in ring-tailed lemurs, slow loris, bushbabies, common marmosets, talapoins, tamarins, squirrel monkeys, patas monkeys, African green monkeys, mangabeys, and macaques; present with triad of lesions at necropsy: multifocal hepatic and splenic necrosis or abscesses, mesenteric lymphadenopathy, and ulcerative enterocolitis
  1. Ring-Tailed lemur: First reported case of osteomyelitis due to Yersinia in a NHP; also caused enteritis, mesenteric lymphadenitis, and abscessation (Walker, J Comp Pathol. 2018)
• Other animals: Similar disease processes reported in meerkats, bats, and lions

 

REFERENCES:

1. Boulianne M. Avian Disease Manual. 8th ed. Jacksonville, FL: American Association of Avian Pathologists, Inc; 2019:114-115.
2. Church ME, Terio KA, Keel MK.  Procyonidae, Viverridae, Hyenidae, Herpestidae, Eupleridae, and Prionodontidae. In: Terio KA, McAloose D, St Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:314.
3. Crespo R, Franca MS, Fenton H, et al.  Galliformes and Columbiformes. In: Terio KA, McAloose D, St Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:760.
4. Delaney MA, Treuting PM, Rothenburger JL.  Rodentia. In: Terio KA, McAloose D, St Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:508-509.
5. Farina LL, Lankton JS.  Chioptera. In: Terio KA, McAloose D, St Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:619-620.
6. Matz-Rensing K, Lowenstine LJ.  New World and Old World Monkeys. In: Terio KA, McAloose D, St Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:358.
7. Percy DH, Barthold SW.   Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: Blackwell Publishing; 2016:186, 230-231, 288.
8. Reavill DR, Dorrestein G.  Psittacines, Coliiformes, Musophagiformes, Cuculiformes. In: Terio KA, McAloose D, St Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:791.
9. Schlafer DH, Foster RA.  Female Genital System. In: Maxie MG, ed. Jubb, Kennedy, and Palmer's Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016:413-414.
10. Schmidt RE, Reavill DR, Phalen DN. Pathology of Pet and Aviary Birds. 2nd ed. Ames, IA: John Wiley and Sons, Inc; 2015:103, 184-185.
11. Simmons J, Gibson S. Bacterial and Mycotic Diseases of Nonhuman Primates. In: Abee CR, Mansfield K, Tardif S, eds. Nonhuman Primates in Biomedical Research. Vol 2. 2^nd Ed. San Diego, CA: Academic Press;2012:138-141. 
12. Spagnoli ST, Gelberg HB.  Alimentary System and the Peritoneum, Omentum, Mesentary, and Peritoneal Cavity.  In: Zachary FJ, ed. Pathologic Basis of Veterinary Disease.  7th ed. St. Louis, MO: Elsevier; 2022:453.
13. Trupkiewicz J, Garner MM, Juan-Salles C.  Passeriformes, Caprimulgiformes, Coraciiformes, Piciformes, Bucerotiformes, and Apodiformes. In: Terio KA, McAloose D, St Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:811.
14. Valli VEO, Kiupel M, Bienzle D.  Hematopoietic System. In: Maxie MG, ed. Jubb, Kennedy, and Palmer's Pathology of Domestic Animals.  Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016:209-210.
15. Uzal FA, Plattner BL, Hostetter JM.  Alimentary system.  In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals.  Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:176-177.
16. Walker D, Gibbons J, Harris JD, et al. Systemic Yersinia pseudotuberculosis as a Cause of Osteomyelitis in a Captive Ring-tailed Lemur (Lemur catta). J Comp Pathol. 2018;164:27-31.
17. Womble M, Cabot ML, Harrison T, et al. Outbreak in African lions of Yersinia pseudotuberculosis infection, with aberrant bacterial morphology. J Vet Diagn Invest. 2022;34(2):334-338. 

 

 

 

 

 

 

 

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