JPC SYSTEMIC PATHOLOGY

REPRODUCTIVE SYSTEM

December 2024

R-B03

 

SLIDE A: SIGNALMENT: 4-year old male bison 

 

HISTORY: This bison had strong positive titers for Brucella abortus, and at slaughter, inspectors noted a testicle twice normal size

 

HISTOPATHOLOGIC DESCRIPTION: Testis: Effacing 80% of the normal architecture and compressing, separating, surrounding, and replacing seminiferous tubules are multifocal to coalescing regions of necrotic debris admixed with degenerate neutrophils, intra and extracellular 1x2 um coccobacilli, and foci of mineral that are further surrounded by epithelioid macrophages, multinucleate giant cells, fewer lymphocytes, and reactive fibroblasts (coalescing granulomas). These areas are further surrounded by abundant collagen (fibrosis) forming thick bands that dissect between granulomas. The inflammatory infiltrate and fibrosis extends into the adjacent tunica albuginea. There is diffuse germ cell atrophy with lack of spermatids in the remaining seminiferous tubules. 

 

MORPHOLOGIC DIAGNOSIS: Testis: Granulomas, multiple, with numerous coccobacilli, germ cell atrophy and aspermia, Bison (Bison bison), bovine.

 

SLIDE B: SIGNALMENT (JPC #1713947): Bovine fetus

 

HISTORY: This fetus was aborted

 

HISTOPATHOLOGIC DESCRIPTION: Lung: Multifocally and randomly affecting 50% of the lung, filling alveolar spaces and adjacent small bronchiole lumina are nodular aggregates of numerous macrophages and degenerate neutrophils, few multinucleated giant cells, lymphocytes, plasma cells, abundant fibrin, edema, and scant hemorrhage. There is multifocal alveolar septal necrosis, with replacement by a similar population of inflammatory cells, necrotic debris, and fibrin. The pleura, interlobular septa, and associated lymphatics are expanded by moderate edema, fibrin, and hemorrhage and small aggregates of macrophages, lymphocytes, and plasma cells.

 

Liver: Multifocally infiltrating portal areas and randomly scattered throughout the parenchyma are low to moderate numbers of lymphocytes and plasma cells with fewer neutrophils and macrophages. There is multifocal extramedullary hematopoiesis.

 

MORPHOLOGIC DIAGNOSIS: 1. Lung: Bronchopneumonia, pyogranulomatous, multifocal to coalescing, moderate, with interlobular edema and pleuritis, breed unspecified, bovine.

2. Liver: Hepatitis, periportal and random, lymphoplasmacytic, multifocal, mild.

 

SLIDE C: SIGNALMENT (JPC #2020923): Goat

 

HISTORY: This goat had aborted

 

HISTOPATHOLOGIC DESCRIPTION: Uterus and placenta (placentome): Multifocally and extensively filling caruncular crypts and effacing chorionic villi are large areas of lytic necrosis characterized by loss of architecture and replacement by eosinophilic cellular and karyorrhectic debris admixed with numerous degenerate neutrophils, macrophages, and colonies 1x2 µm basophilic coccobacilli. Bacteria are also present within macrophages, cytotrophoblasts, and syncytiotrophoblasts. Multifocally less affected chorionic villi contain necrotic multinucleated syncytiotrophoblasts (shrunken with hypereosinophilic cytoplasm and pyknotic nuclei) and/or are multifocally denuded. Diffusely, the lamina propria of the caruncle/uterus and intercotyledonary area of the placenta is edematous and expanded by mucin and low numbers of neutrophils and macrophages. Caruncular vessel walls are infiltrated by similar inflammatory cells, necrotic debris, and fibrin (necrotizing vasculitis) and vessel lumina often contain fibrin thrombi.

 

MORPHOLOGIC DIAGNOSIS: Uterus with placenta (placentome): Placentitis, necrotizing, acute, focally extensive, severe, with necrotizing vasculitis, fibrin thrombi, and numerous intratrophoblastic, intrahistiocytic, and extracellular colonies of coccobacilli, breed unspecified, caprine.

 

ETIOLOGIC DIAGNOSIS: Testicular, hepatic, pulmonary, and placental brucellosis

 

CAUSE: Brucella abortus

 

CONDITION: Brucellosis

 

SYNONYMS: Undulant fever, Bang's disease

 

GENERAL DISCUSSION: 

• Bovine brucellosis is a worldwide, zoonotic disease caused by Brucella abortus of many domestic and wild animals that causes systemic and chronic infections with recurrent bacteremia which often manifests as late term abortions, fetal bronchopneumonia, orchitis, epididymitis, and osteomyelitis
• Brucella sp. are small, 0.4-1.5 um long, gram-negative, facultatively intracellular, bacilli to coccobacilli
• Smooth strains of Brucella spp. express O side chain on LPS, rough strains (B. ovis and B. canis) do not
• Major sources of infection: Aborted fetus, placenta, uterine discharge 

 

PATHOGENESIS:

• Route of infection: Ingestion, conjunctival, vaginal, cutaneous, coital
• Localization restricted to: Spleen, mammary glands, mammary lymph nodes, pregnant uterus of females; lymphoid tissue, testis and accessory glands of males; can localize in synovium
  • Affinity for pregnant endometrium and fetal placenta
• Transmission by contact, often ingestion, with infected tissues, secretions or excretions (milk, fetal tissues, placenta, etc.) > phagocytosis by macrophages, endocytosis/transcytosis or penetration of mucosa and M cells > regional lymph node, Peyer’s patches > lymphadenitis, replication within mononuclear phagocytic cells (macrophages are the preferred cell for Brucella); > bacteremia > dissemination to mammary gland (especially colostrum), reproductive organs, placenta, fetus, other lymph nodes > Invade or are phagocytosed by trophoblasts > massive intracellular replication of Brucella in trophoblast cells > fetal infection; 
  • Replication in the rough endoplasmic reticulum of trophoblasts
  • When Brucella abortus is ingested with feed contamination the initial lesion is a persistent nasopharyngeal lymphadenitis
  • Placental trophoblasts produce erythritol and steroid hormones, which is theorized to contribute to tropism for the pregnant uterus/placenta due to an unknown effect
• Doesn’t produce toxins, rather cell lysis is due to inflammation and inflammatory mediators and enzymes
• Smooth strains (more virulent): Cellular entry through interaction with lipid rafts in the plasma membrane via the Brucella LPS O-polysaccharide (O side chain); capable of intracellular replication due to prevention of phago-lysosomal fusion and inhibition of macrophage apoptosis
• Rough strains: LPS deficient, don’t interact with lipid rafts; defective at intracellular replication
• Evasion of immune response:
  • Evade killing upon phagocytosis by blocking phagosome-lysosome fusion through rapid acidification of the phagosome
    • LPS (a PAMP), a type IV secretion system and other virulence factors (such as cyclic ß-1,2-glucan and heat shock proteins) involved
  • Able to grow and replicate in macrophages and dendritic cells
• Latent infections can occur but mechanism is unknown

 

TYPICAL CLINICAL FINDINGS:

• Young cattle relatively resistant until puberty
• Retained placentas, metritis, infertility, late term abortions or birth of non-viable calf
• Scrotal swelling 
• Mastitis 
• Synovitis/arthritis
• Enlarged lymph nodes

 

TYPICAL GROSS FINDINGS: 

• Placenta: Extensive non-uniform necrosis of cotyledons with brown exudate; intercotyledonary / periplacentomal areas thickened by edema and viscous exudate between the endometrium and chorion with leathery surface appearance; necrosis and inflammation of intervillous portions (placental arcades); inflamed and expanded maternal septa leading to placental interlocking and increased risk of retained placenta
  • Placentitis is not evenly distributed and often leads to acute diffuse endometritis
• Uterus: Slowly developing lesions; exudate between endometrium and chorion; in sows, miliary uterine brucellosis may develop characterized by numerous, small granulomas within the mucosa
• Testicle/epididymis/accessory sex glands: Chronic epididymitis/orchitis, sperm granulomas, periorchitis, vesicular adenitis (seminal vesiculitis), prostatitis
• Fetus: Fibrinous bronchopneumonia (most important fetal lesion especially in those aborted in the last half of pregnancy), pleuritis, and pericarditis, with fluid in body cavities; splenitis; lymphadenitis, nephritis, pericholangitis
• Hygromas in cervids with B. abortus

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Testis: 

• Necrotizing orchitis/epididymitis; necrotizing vasculitis
• Fibrinopurulent serositis of visceral and parietal tunics 
• Necrotic tubular epithelium with numerous organisms; predisposition to sperm granulomas
• In rams with B.ovis infection, the epididymal tail is most commonly affected and there is epithelial hyperplasia, degeneration, and the formation of intraepithelial lumina; unlike bulls, ram infections with Brucella spp usually do not have an associated orchitis

• Orchitis: Three main categories

1. Interstitial: Typically not recognized macroscopically; lymphocytic infiltration of intertubular stroma (can be a normal aging finding) with fibrosis
2. Intratubular: Inflammation focused on the seminiferous tubules; may be due to ascending infection; solitary or multiple yellow-white nodules up to 1 cm; retention of tubular outline but loss of tubular epithelium with replacement by macrophages, multinucleate giant cells that surround neutrophils, and cellular debris +/- sertoli cell hyperplasia and mineralization
3. Necrotizing: Characteristic of Brucella spp.; coagulative necrosis bordered by fibrosis and inflammatory cells  +/- abscessation and fistulation  

• Placenta: 

• Necrotizing placentitis with periarteritis and arteritis, edema, and macrophages and neutrophils
• Numerous coccoid bacteria in the chorionic epithelium (trophoblasts); most severely affected trophoblasts are at base of villi and crypts of caruncle; sloughing of chorionic epithelium 
• Most severely affected area of placenta is the intervillus portion (placental arcades)

• Fetus: 

• Fibrinous bronchopneumonia (P-B14) with predominantly mononuclear cells and variable numbers of neutrophils; pulmonary septal edema, necrotizing arteritis
• Focal necrosis and granulomatous inflammation in lymph nodes, liver (hepatocellular necrosis and pyogranulomatous portal hepatitis), spleen, kidney, meninges, and fibrinous pericarditis

• Uterus: Mild (early) to severe (late) lymphoplasmacytic and histiocytic to pyogranulomatous/granulomatous metritis with caruncular necrosis; numerous bacteria in epithelial cells 

• Non-specific acute, diffuse endometritis with placentitis occurring first

• Seminal vesicle: Fibrinopurulent to necrotizing inflammation often with dystrophic calcification, and rarely granulomas
• Mammary gland: Focal lymphoplasmacytic and histiocytic interstitial inflammation, neutrophil exudation in alveoli and occasional lymphoid follicles 

• Chronic infection leading to thickened interlobular septa and atrophy of alveoli; often no grossly detectable lesions

• Carpus: Nonsuppurative synovitis  
• Lymphoid tissue: Pyogranulomatous lymphadenitis; lymphoid hyperplasia with medullary hemorrhage (no fibrosis or necrosis)

 

ADDITIONAL DIAGNOSTIC TESTS: 

• Serology: Serum agglutination, complement fixation, ELISA
• PCR
• Milk ring test
• Culture maternal caruncle, placenta, stomach contents, lung
• Direct placental smear stained with Stamp’s or Kosters’ stain

 

DIFFERENTIAL DIAGNOSIS: 

Abortion:

Bovine:

• Mycotic placentitis (Absidia sp., Mucor sp., Aspergillus sp., Rhizopus sp.): Necrotic cotyledons and intercotyledonary areas; dry, leathery placenta; ringworm-like dermal lesions on fetus; lower rate of abortion 
• Trichomonas fetus: Early term abortion; infertility, or pyometra and fetal maceration common
• Campylobacter fetus: Late term abortion; lower abortion rate; infertility; placental edema and petechia
• Neospora caninum: Abortions at 3-8 months of gestation and mummification; nonsuppurative necrotizing encephalitis and myocarditis with protozoal cysts and zoites
• Leptospirosis (L. pomona and L. hardjo): Late term abortions; brown gelatinous edema between amnion and allantois; yellow-brown cotyledons
• Infectious bovine rhinotracheitis (bovine herpesvirus-1): Late term abortions; hepatic necrosis with intranuclear viral inclusions in fetus 
• Trueperella sp.: Abortion, suppurative placentitis, and fetal lung lesions; will see colonies of bacteria with the fetal pneumonia
• Bovine viral diarrhea virus (Bovine pestivirus): Early term abortions or weak calves with cerebellar hypoplasia; detection of virus in fetal tissues to diagnose
• Listeria monocytogenes: Late gestation abortion; vasculitis in chorioallantoic stroma; foci of necrosis in liver and other organs
• Epizootic bovine abortion (Foothill abortion, R-B01) caused by Pajaroellobacter abortibovis: Seasonal, tick-borne disease in the Rocky Mountain foothills; late term abortions; fetus with edema, hemorrhages in multiple tissues; lymphohistiocytic inflammation in many viscera, marked hepatic RE cell hyperplasia, granulomatous thymitis, lymphadenitis, pneumonia, and encephalitis
• Ureaplasma diversum: Necrotizing placentitis, amnionitis, with fibrosis, mineralization, heavy mononuclear cell infiltrate, foci of necrosis and hemorrhage, mild vasculitis; fetal conjunctivitis and nonsuppurative pneumonia
• Other bacterial causes: Salmonella spp., Staphylococcus spp., Streptococcus spp., Histophilus somni, and Mycoplasma spp.

Ovine / Caprine:

• Brucella ovis: Placentitis with periarteritis and arteritis; coital transmission 
• Brucella melitensis: Resembles bovine brucellosis; abortion may be only sign, especially late in pregnancy
• Chlamydia abortus: Necrosis of cotyledons; infects trophoblasts and endometrial epithelium, vasculitis
• Coxiella burnetii (Q fever): Intercotyledonary necrotizing placentitis and characteristic intratrophoblastic organisms giving a “foamy” appearance.
• Toxoplasma gondii: Necrosis in cotyledon with normal intercotyledonary areas; protozoa within trophoblasts
• Campylobacter jejuni (predominant cause of ovine abortions in US), C. fetus var. venerealis: Metritis in ewes; enlarged, pale yellow to tan cotyledons covered with a brown exudate; targetoid hepatic necrosis in fetus
• Rift Valley Fever (Bunyavirus-Phlebovirus): Foci of hepatic necrosis in fetus; fetal hydranencephaly; prolonged gestation

Swine: Causes of abortion, stillbirth, and/or mummification

• Viral: 
  • Porcine reproductive and respiratory syndrome virus (Arterivirus)
  • Porcine Circovirus 2
  • Parvovirus
  • Pseudorabies virus
  • Enterovirus (Teschovirus)
  • Classical swine fever (Pestivirus)
  • Bovine pestivirus
  • Border disease virus (Pestivirus)
  • Japanese encephalitis virus (Flavivirus)
  • Cytomegalovirus (Betaherpesvirus)
• Bacterial:
  • Brucella suis (more common): Abortion between the second and third month of pregnancy; placentitis
  • Leptospirosis (more common): Mummification of fetuses
  • Chlamydia sp.
• Non-infectious: Carbon monoxide, Zearalenone

 

Orchitis:

Bovine: 

Caprine / Ovine: 

Feline: 

Swine:

• Experimental infection with porcine rubulavirus (Paramyxoviridae), the cause of “blue eye”, may cause orchitis and epididymitis
• Burkholderia pseudomallei, Trueperella pyogenes, Streptococcus zooepidemicus, and Streptococcus equisimilis

Equine:

Canine:

 

Epididymitis:

Bovine:

Ovine/Caprine:

Swine: 

Canine:

• Brucella canis, E. coli, Burkholderia pseudomallei, Mycoplasma canis, Blastomyces dermatitidis, Rhodotorula glutinis
• Canine distemper virus; intracytoplasmic and intranuclear inclusions in epithelial cells

Equine:

Feline:

 

COMPARATIVE PATHOLOGY:

Other Brucella spp. of veterinary importance:

• Brucella melitensis: Principal cause of brucellosis in sheep, goats, and camelids; similar to bovine brucellosis although less protracted in sheep and spontaneous recovery common; late term abortion may be only sign; inflammation is localized to the mammary gland and pregnant uterus
• Brucella ovis: Sheep: least virulent of the Brucella sp.; abortion, stillbirth, epididymitis, ampullitis, suppurative orchitis with subsequent ductal epithelial hyperplasia; coital transmission; fetus show minimal histologic evidence of systemic infection; sperm granulomas are characteristic
• Brucella suis: Pigs (also B. melitensis, rarely B. abortus); transmission mainly coital; testicular abscessation, predilection for bone and joints; focal granulomatous lesions with coagulative necrosis; granulomatous and necrotizing orchitis, abortions in 1^st trimester (unlike ruminants), weak or stillbirths, suppurative endometritis, granulomas with multiple hyperplastic lymphoid nodules, fibrinopurulent osteomyelitis and diskospondylitis
• Brucella canis: Dog: Abortion usually after 50d gestation, epididymitis with subsequent testicular degeneration and atrophy, prostatitis, scrotal dermatitis, endophthalmitis; fetal endocarditis, pneumonia and hepatitis; rtPCR and IHC on formalin-fixed paraffin embedded (FFPE) tissue is promising to detect this organism that is classically difficult to diagnose (Camargo-Castañeda, J Vet Diagn Invest. 2021)
• Brucella abortus and B. suis are commonly associated with bursitis in horses (poll evil and fistulous withers)
• Marine mammals: B. ceti and B. pinnipedialis: placentitis, abortions, orchitis, and blubber abscesses, hepatic/splenic/lymph node necrosis, osteoarthritis, mastitis, endometritis, pneumonia; endocarditis and nonsuppurative meningoencephalitis (neurobrucellosis) in young striped dolphins, Atlantic white-sided dolphins, short-beaked common dolphins, long-finned pilot whales, and a recent report in Sowerby’s beaked whales (Davison, J Comp Pathol. 2021) 
• Cats resistant to natural infection by Brucella sp.
• Guinea pigs susceptible and used as model of brucellosis; natural infection rare
• B. intermedia: Rabbits; rare; important reservoir of B. suis (also B. melitensis and B. abortus
• B. ceti: (also B. pinnipedalis) Cetaceans, zoonotic; often overcome infection and become shedders and carriers; affects reproductive (endometritis, placentitis, abortion, epididymitis, orchitis), CNS (meningoencephalomyelitis, acquired hydrocephalus, predilection for cerebellum, brainstem, spinal cord, and medulla) and musculoskeletal (discospondylitis, osteoarthritis, DJD) systems
• B. pinnipedialis: Pinnipeds, may be vectorborne (lungworm); often subclinical; necrosuppurative placentitis

 

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