JPC SYSTEMIC PATHOLOGY
REPRODUCTIVE SYSTEM
January 2022
R-B07

Signalment (JPC #1758839):  African pygmy goat

HISTORY:  Multiple near-term abortions occurred in a research herd of African pygmy goats.  Placentas were covered with tan, mucoid exudates, cotyledons were hemorrhagic, and necrotic villi were noted.  Cultures of fetal stomach contents were negative for bacterial growth.

Slide A:  HISTOPATHOLOGIC DESCRIPTION:  Placenta (chorioallantois), cotyledon and intercotyledonary area:  Diffusely affecting the cotyledon, there is effacement of the chorioallantoic villar architecture with degeneration, necrosis, and loss (ulceration) of the chorionic epithelium with replacement by abundant necrotic debris (lytic necrosis), hemorrhage, fibrin, edema, and scattered sloughed cytotrophoblasts and syncytiotrophoblasts, admixed with numerous degenerate neutrophils and fewer macrophages, lymphocytes, and plasma cells. Multifocally the intervillous space is expanded by abundant necrotic debris, degenerate neutrophils, fibrin, hemorrhage, and edema. Multifocally, there are numerous 1 um, pleomorphic, coccoid to rod-shaped bacteria expanding the cytoplasm of trophoblasts and less commonly macrophages. Near the base of the cotyledon are multifocal areas of basophilic finely granular to fragmented material (mineral). The chorioallantoic stroma is multifocally expanded by clear space (edema), ectatic lymphatics, and moderate numbers of lymphocytes, plasma cells, and fewer macrophages. The chorionic epithelium of the intercotyledonary chorioallantois is diffusely thickened and ulcerated with epithelial replacement by degenerate neutrophils, fibrin, hemorrhage, edema, and necrotic debris.

Slide B: Giemsa:  Intratrophoblastic coccobacilli stain blue to purple.

MORPHOLOGIC DIAGNOSIS:  Placenta (chorioallantois), cotyledon and intercotyledonary area:  Placentitis, necrotizing and suppurative, subacute, diffuse, severe, with numerous intratrophoblastic and intrahistiocytic coccobacilli, African pygmy goat, caprine.

ETIOLOGIC DIAGNOSIS:  Coxiella placentitis

CAUSE:  Coxiella burnetii

CONDITION:  Q Fever (“Query fever”) in man

GENERAL DISCUSSION:

• Gram negative, obligate intracellular, intracytoplasmic protobacteria of the order Legionellales (formerly Rickettsiales); worldwide distribution; causes late gestational abortion in ruminants
  • Phylogenetically related to Legionella, Francisella, and Rickettsia
• Ruminants (dairy cows, goats, sheep) are the most common reservoir; other hosts include cats, wild ruminants, pigs, rodents, humans, birds, Pacific harbor seals, and arthropods
  • Infection persists indefinitely in sheep and cattle. Coxiella may be present in large numbers in the placenta of infected subclinical animals
  • Sheep and goats often co-infected with Chlamydia and Toxoplasma
• Identified in most tick species (theorized burnetti evolved from a tick endosymbiont) and experimentally transmitted by Rhipicephalus spp, Ornithodoros spp, and Ixodes spp.
• Usually transmitted by inhalation of environmentally resistant organisms (can travel up to 10 miles via wind), ingestion, direct contact with body fluids and vectors
• Large numbers of organisms are present in infected placenta and fetal membranes; organisms also present in wool, feces, and milk
• Sporulates; resistant to heat (pasteurization temperature targeted to kill this organism), drying, and to physical and chemical agents; survives for long periods
• Zoonotic, OIE reportable

PATHOGENESIS:

• Two life cycle stages:
  • Large cell form is metabolically active intracellular vegetative stage
  • Small-cell extracellular variant is metabolically inactive, environmentally resistant stage
• burnetii infects cells of the macrophage lineage and trophoblasts (which have a phagocytic function and undergo apoptosis as a normal part of placental growth/separation); survives in autolysosome-like compartments
  • Inhibits apoptosis in host cells potentially via inhibition of the release of cytochrome C, preventing activation of executioner caspases
  • Downregulates macrophage responses to lymphokines and induction of suppressor factors
  • Causes defective phagosome maturation and impairs antimicrobial activities
• Abortions usually follow initial exposure; abortions are less common in endemically infected herds/flock
• Transmitted to the fetus either hematogenously, affecting mainly the liver, or transplacentally via contaminated amniotic fluid, causing pneumonia and enteritis

TYPICAL CLINICAL FINDINGS:

• Inapparent infection in most animals
• Abortions in last trimester, usually following initial exposure
• Weak and stillborn neonates

TYPICAL GROSS FINDINGS:

• Thickened, leathery placenta, with coalescing areas of mineralization
• Copious, off-white exudate covers intercotyledonary areas
• Cotyledons may have white outer ring with central scattered white flecks
• Aborted fetus may be well preserved or autolyzed

TYPICAL LIGHT MICROSCOPIC FINDINGS:

• Acute, diffuse, suppurative placentitis with extensive necrosis of cotyledonary villi and intercotyledonary epithelium (i.e. both cotyledonary and intercotyledonary areas affected)
  • Suppurative inflammation most severe in intercotyledonary areas and cotyledon periphery
  • Mononuclear (especially plasma cells) inflammation in the chorioallantoic interstitium
• Vasculitis is not usually a feature (vs. Chlamydia infection)
• Hypertrophic trophoblasts distended with microcolonies of Coxiella organisms
  • Cells containing organisms frequently have a characteristic foamy appearance with multiple unstained vacuoles within finely granular blue cytoplasm (vs. Chlamydia inclusions which stain poorly and appear more homogenous), and the nucleus is peripherialized/crescent shaped
• Fetal lesions are usually mild and include a granulomatous hepatitis and nonsuppurative pneumonia with occasional focal peribronchiolar lymphoid accumulations

ADDITIONAL DIAGNOSTIC TESTS:

• Smears of placental exudate contain large numbers of organisms
  • Organisms stain well with modified Ziehl-Neelsen, Stamp, Gimenez, or Macchiavello stains
• Culture (BSL-3 lab required because of zoonotic potential)
• Placental immunohistochemistry: Antigen present in cytoplasmic vacuoles of trophoblasts, especially along the base of the chorionic villi and in neutrophils, degenerate cells, and extracellularly in the intervillous spaces
• Fluorescent antibody staining of tissue or smears of placental exudate
• Serologic titers from dam; complement‑fixation; indirect fluorescent antibody; ELISA
• PCR assays

DIFFERENTIAL DIAGNOSIS:

Abortions in small ruminants:

• Necrotizing placentitis associated with intra-trophoblastic organisms:
  • Brucella ovis: Caramel colored, sticky exudate on the placenta, thick leathery placenta, and vasculitis
  • Chlamydia abortus (R-B08): Vasculitis common; coccoid organisms form intracytoplasmic “inclusions” that stain poorly and appear homogenous
  • Toxoplasma gondii: Affects primarily cotyledons
• Campylobacter fetus: Placental lesions are more severe over the placentomes; vasculitis; characteristic targetoid lesions on fetal liver (hepatic necrosis)
• Listeria monocytogenes: Severe placental lesions; necrotic tips of villi covered by purulent exudate in which many bacteria are present
• Sarcocystis cruzi: Abortion in cattle, goats, sheep; acute necrotizing endometritis; zoite-containing cysts; multiple foci of necrosis in fetal soft tissues

COMPARATIVE PATHOLOGY:

1. burnetti in other species:

• Cattle: Abortion and placental lesions similar to sheep and goats, however severe lesions are rare (bovids usually subclinical)
  • Intralesional burnetii has been found within macrophages of infertile cows with endometritis in the absence of other pathogens, suggesting C. burnetti may be the cause (De Biase et al., Vet Pathol. 2018)
• Non-domestic ruminants (waterbuck, sable antelope, dama gazelle, Cuvier’s gazelle, greater kudu, bongo, and giraffe): Coxiella-associated placentitis, abortion, and stillbirth have been reported
• Mice: burnetii infection documented in C.B-17-scid/beige mice xenotransplanted with fetal bovine tissue, developed multifocal necrotizing hepatitis with intracytoplasmic organisms within Kupffer cells
• Humans: Variety of nonspecific signs; chronic infection may result in endocarditis
• Birds:
  • burnetii: Non-clinical infection
  • Other Coxiella (Avian Coxiellosis): more pathogenic; non-specific clinical signs, emaciation, splenomegaly, hepatomegaly, granulomatous encephalitis and myocarditis, and Coxiella-like organisms within macrophages of the spleen, liver, bone marrow, kidneys, and adrenal glands

REFERENCES:

1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits. 4th ed. Ames, IA: John Wiley and Sons; 2016:61-62.
2. Botta C, Pellegrini G, Hassig M, et al. Bovine fetal placenta during pregnancy and the postpartum period. Vet Pathol. 2019; 56(2):248-258.
3. De Biase, Costagliola A, Del Piero F, et al. Coxiella burnetii in infertile dairy cattle with chronic endometritis. Vet Pathol. 2018; 55(4):539-542.
4. Delaney MA, Hartigh AD, Carpentier SJ, et al. Avoidance of the NLRP3 inflammasome by the stealth pathogen, Coxiella burnetii. Vet Pathol. 2021; 58(4):624-642.
5. Flanders AJ, Speer B, Reavill DR, et al. Development and validation of 2 probe-hybridization quantitative PCR assays for rapid detection of a pathogenic Coxiella species in captive psittacines. J Vet Diagn Invest. 2020; 32(3):423-428.
6. Foster RA. Female reproductive system and mammae. In: McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:1183.
7. Jones MEB, Gasper DJ, Mitchell E. Bovidae, Antilocapridae, Giraffidae, Tragulidae, Hippopotamidae. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Academic Press; 2018:136-137
8. Macias-Rioseco M, Riet-Correa F, Miller MM, et al. Bovine abortion caused by Coxiella burnetii: report of a cluster of cases in Uruguay and review of the literature. J Vet Diagn Invest. 2019; 31-(4):634-639.
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; 2016:416-417.

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