Conference 7 - 2016 Case: 3 20161019

Signalment:

Age unspecified female Columbia X Rambouillet ewe (Ovis aries).A flock of 7500 ewes were grouped in mobs of 1500. Over the course of the 2016 lambing season, 1200 ewes, ranging in age from 2 8 years aborted. Abortions continued even after feeding tetracycline pellets. At the end of the lambing season, older aborted ewes were culled and younger recovered ewes were mixed with ewe lambs as a vaccination strategy.

Gross Description:

Three fetuses and placentas were markedly autolyzed and had no significant gross lesions. A fourth placenta was in good to fair post-mortem condition. That placenta had inter-cotyledonary edema and multifocal tan-grey discoloration of cotyledons.

Histopathologic Description:

Both cotyledonary and intercotyledonary areas were characterized by necrosis of tropho-blastic and intercoteledonary epithelium, with hypereosinophilic shrunken cytoplasm and karyorrhectic or karyolytic nuclei. Foci of necrosis were expanded by necrotic cellular debris and large numbers of degenerate neutrophils within the immediate underlying chorioallantoic connective tissue. Several areas of necrosis are associated with many clustered bacilli. Adjacent tropho-blasts often contain small intracytoplasmic bacilli. Rare trophoblasts contain, intra-cytoplasmic, 2 μm diameter, basophilic material. Scattered throughout the chorioallantois, many blood vessels are surrounded by neutrophils and a few vessels are partially occluded by large aggregates of fibrin and neutrophils. Rare small vessels are lined by necrotic endothelial cells with separation of the wall by neutrophils and fibrin (fibrinoid necrosis). Diffusely the chorioallantoic connective tissue is expanded by edema and all vessels are markedly congested.

Similar lesions were seen in placentas from the other fetuses submitted. No significant lesions were identified in any of the fetal tissues.

Morphologic Diagnosis:

Placentitis, necrosuppurative, cotyledonary and intercotyledonary, diffuse, severe, with necrotizing vasculitis and bacteria.

Lab Results:

Numerous Campylobacter jejuni were isolated from one of four placentas. Other tests performed with negative results included FA for Leptospira interogans, ELISA for Chlamydophila sp. and PCR for pestivirus. Selenium level in one of three livers was marginal. Immunohistochemistry for Coxiella burnetii on fixed placenta was negative. In two previous submissions from the same farm, C. jejuni was isolated from fetal tissue pools, stomach contents or placentas from four additional aborted fetuses.

Condition:

Necrosupporative placentitis/Campylobacter jejuni

Contributor Comment:

Campylobacter jejuni is one of three species in the genus causing reproductive and enteric disease in a variety of animal species and in humans.⁸ C. fetus subsp. venerealis primarily causes infertility and abortion in cattle, whereas C. fetus subsp fetus and C. jejuni are important causes of abortion in small ruminants and occasionally cattle. C. jejuni is an important cause of food-borne illness in people and has become an increasingly important cause of late term abortions in small ruminants.⁴ Abortions have also been documented in humans and in dogs.⁶ In sheep, infection by either C. fetus fetus or C. jejuni causes late term abortion, still birth or weak lambs. Transmission is by the oral route. Placentas are not retained and often have gross lesions of intercoteledonary edema and cotyledonary necrosis. Aborted fetuses may have characteristic gross lesions of necrotizing hepatitis and histologic lesions of suppurative bronchopneumonia (neither present in this case). Occasionally ewes become ill and die due to endometritis.⁸

Campylobacter is reportedly the most common cause of abortion in sheep and C. jejuni is now the most common species to cause abortion in sheep flocks.⁴ Recently, a single clone of C. jejuni (SA) has been shown experimentally to cause abortion in sheep⁹ and it is genetically similar to clones causing gastroenteritis in people.⁵ In addition, most isolates of C. jejuni from sheep abortions in the United State (including the one in this case) are highly resistant to tetra-cyclines, the only approved drug for treating infection in sheep.⁴ In contrast, isolates from the United Kingdom are susceptible to tetracyclines⁹, suggesting common treatment of sheep abortions with teracyclines in this country may have led to the emergence of the resistant clone. Drug resistance and links to human enteric disease indicate that owners, veterinarians, and laboratory personnel should be cautioned about zoonotic potential when handling suspect fetal tissues.

Other important differential diagnoses for placentitis in sheep and goats include Brucella ovis, Brucella mellitensis, Toxoplasma gondii, Chlamydophila abortus and Coxiella burnetii.⁸ The most common manifestation of ovine brucellosis in the US is epididymitis in rams; abortion with placentitis is less common. Toxoplasma gondii should have characteristic gross and histologic lesions, with the presence of organisms within the placental lesions, but can also be ruled out by PCR. The three main differentials, in this case, are C. jejuni, C. abortus and C. burnetii due to the presence of intracellular bacteria on H&E. The bacteria were not positive with the Gimenez stain, making diagnosis of the two latter organisms less likely. C. abortus was eliminated by Ag ELISA on the placenta and C. burnetii by immunohistochemistry. Because of the high likelihood of encountering zoonotic agents associated with small ruminant abortions, examination of all sheep and goat abortuses, especially if accompanied by fetal membranes, should be performed in a biosafety cabinet.

JPC Diagnosis:

Placenta, cotyledonary and intercodyledonary: Placentitis, necrosuppurative, diffuse, severe with necrotizing vasculitis.

Conference Comment:

The contributor provides a concise summary of abortion in small ruminants caused by a Campylobacter spp as well as other important differential diagnoses for abortion in these animals. Despite some minor slide variability, conference participants unanimously noted the outstanding preservation and high quality of the section of placenta in this case.

Prior to discussing the case, the conference moderator spent some time reviewing placentation in ruminants. The different components of the placenta were discussed and participants identified individual layers and their orientation within the tissue section. All ruminants have cotyledonary villous epitheliochorial nondeciduate placentation. The placenta is comprised of the maternal endometrium and the fetus derived fused chorioallantoic membranes (CAM). Because ruminant placentas are nondeciduate, the maternal endometrium and fetal CAM are in contact but they do not fuse. In addition, in cotyledonary placentation, there are multiple areas where the CAM villi insert into pockets or crypts in the area of the endometrium known as the placentome, which is a combination of the fetal cotyledon and maternal caruncle. Specific to small ruminants, the caruncles have lost their epithelium, leaving five tissue layers which separate maternal and fetal blood: endothelium, connective tissue, epithelium of the CAM, and endothelium and connective tissue of the endometrium.¹

Conference participants noted that, in this case, there are multifocal brown globular pigment present in the maternal side of the placenta in the subchorial area where hematoma and hemophagocytosis are often most prominent and a normal finding. Additionally, thrombosis within the chorionic plate , present in some slides in this case, is also a normal finding in the post-partum placenta. However, if there is similar brown staining material on the CAM, it could be indicative of meconium deposition, which is a result of pre-parturient fetal stress. Meconium staining was not seen by conference participants in this case.

Transmission of Campylobacter spp. often occurs via fecal-oral route most commonly through contamination of water supplies.⁸ The organism is a common commensal bacterium in the intestinal tract of cattle, sheep, and swine as well as dogs, cats, and rodents. When taken in orally in susceptible animals, there is a transient bacteremia. The bacteria are then localized to the gut and bile. In pregnant ewes, the bacteria localize to the uterus via the Surface (S)-layer protein, which is thought to allow the bacteria to colonize and translocate from the uterus to the placenta and subsequent abortion in about 25% of cases.⁸

Characteristic findings of campylo-bacteriosis are edematous intercotyledonary areas and friable yellow cotyledons with necrotizing and suppurative placentitis and vasculitis most severe in chorionic villi. There will often be large dense Gram-negative bacterial emboli within chorionic capillaries, although that was not a prominent feature in this case.⁸ However, numerous Campylobacter spiral organisms are present throughout the tissue and easily visualized on the Warthin-Starry silver stain. Many conference participants noted intra-cellular bacilli within trophoblasts on the H&E. In the fetus, there will typically be yellow hepatic foci with targetoid depressed red centers (necrotizing hepatitis) and fibrinous peritonitis.⁸

References:

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3. Hazlett MJ, McDowall R, DeLay J, et al. A prospective study of sheep and goat abortion using real-time polymerase chain reaction and cut point estimation shows Coxiella burnetii and Chlamydophila abortus infection concurrently with other major pathogens. J Vet Diagn Invest. 2013; 25(3):359-368.
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8. Schlafer DH and Foster RA. Diseases of the gravid uterus, placenta and fetus In: Maxie MG, ed. Jubb Kennedy and Palmer's Pathology of Domestic Animals. Vol 3. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016:407-408.
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