History
Twin ovine fetuses were submitted without fetal membranes for investigation of the cause of abortion. The male fetuses were near term with crown to rump lengths of 48 and 51 cm and body weights of 2.5 kg (5.5 lb) and 3.7 kg (8.1 lb). The dam was in a group with 6 other ewes; all ewes traveled off-site for artificial insemination. Vaccination status of the dam was unknown. All ewes in the group were clinically normal at the time of submission of the fetuses. Another ewe from the group had aborted about 1 month previously, but that fetus was not submitted for diagnostic testing.
Gross Findings
The lungs of both fetuses were atelectatic. The liver of 1 fetus had coalescing pale tan necrotic foci visible through the hepatic capsule and on cut section (Figure 1). The foci were 5 mm to 6 cm in diameter. The liver of the other fetus was grossly normal. Other gross lesions were not observed.
Photographs of the pleural and peritoneal cavities of I of 2 aborted male ovine fetuses that were submitted without fetal membranes for investigation of the cause of abortion. A—The lung tissue is atelectatic. The liver has coalescing tan foci of necrosis visible through the hepatic capsule. Bar = 3 cm. B—On section, the necrotic foci extend into the hepatic parenchyma. Bar = 1 cm.
Citation: Journal of the American Veterinary Medical Association 257, 2; 10.2460/javma.257.2.157
Formulate differential diagnoses from the history, clinical findings, and Figure 1—then turn the page→
Histopathologic Findings and Bacterial Culture Results
In the fetal liver with gross lesions, hepatic necrosis was mostly lytic and multifocal to coalescing (Figure 2). Fibrin, macrophages, lymphocytes, and fewer degenerated neutrophils were present in the necrotic foci. Fibrin thrombi were evident in small vessels. Neutrophils were present in the lumens of a few bile ducts. The fetus without gross hepatic lesions had suppurative bronchopneumonia, with meconium and desquamated squamous epithelial cells in the alveolar spaces and bronchioles (not shown).
Photomicrographs of a section of liver from the ovine fetus in Figure 1. A—Multifocal to coalescing areas of lytic necrosis are extensive throughout the liver. H&E stain; bar = 100 μm. B—Neutrophils and mononuclear leukocytes are numerous in a necrotic focus. H&E stain; bar = 30 μm. Inset—Higher-magnification view. Notice the short bacterial rods in hepatocytes. Grocott methenamine silver; bar = 15 μm.
Citation: Journal of the American Veterinary Medical Association 257, 2; 10.2460/javma.257.2.157
Samples of abomasal contents, lungs, liver, and spleen from both fetuses were combined and submitted for bacterial culture, which yielded Campylobacter jejuni. The speciation of the Campylobacter isolates was confirmed by comparison of protein spectra obtained via matrix-assisted laser desorption ionization-time-of-flight mass spectrometry against known species spectral references.a Bluetongue virus, bovine viral diarrhea virus, and border disease virus were not isolated from fetal tissues. Results of real-time PCR assays to detect Brucella sp, Chlamydia abortus, Chlamydia psittaci, Coxiella burnetii, Leptospira spp, Neospora caninum, or Toxoplasma gondii were negative.
Morphologic Diagnosis and Case Summary
Morphologic diagnosis and case summary: multifocal necrotizing hepatitis in 1 of 2 fetuses aborted as a result of C jejuni infection in a ewe.
Comments
For the ewe of the present report, the abortion of the twin fetuses was attributed to infection with C jejuni on the basis of the gross and histopathologic findings, pure culture of the organism from fetal tissues, and microbial speciation determined by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry as well as negative results of virus isolation and PCR assays for other infective organisms. Campylobacter jejuni is a gram-negative, microaerophilic, motile, curved bacillus. As an emerging zoonosis, campylobacteriosis is a major economic burden and has serious health implications in both human and veterinary medicine.1 In the United States, C jejuni is one of the most common foodborne pathogens, and infection with this organism causes self-limiting but potentially life-threatening gastroenteritis. In the United States between 2000 and 2008, 9% of the 9.4 million human cases of food poisoning (which included 55,961 instances of hospitalization) were associated with C jejuni infection.2 Raw or undercooked poultry is the most commonly implicated source of C jejuni infection among humans.3 Recent outbreaks of campylobacteriosis in the United States have been associated with raw milk consumption, a muddy foot race, consumption of undercooked chicken livers, and exposure to dogs or puppies from pet stores.4
A 2015 study examined disability-adjusted life years to measure the disease burden in terms of disability and death of humans with C jejuni infections in the United States. Based on the 2006 US census population of 293 million, foodborne pathogens caused 112,000 disability-adjusted life years annually with 22,500 attributed to C jejuni infection.5 Most human enteric infections are self-limiting, but sequelae include arthritis and Guillain-Barré syndrome. Guillain-Barré syndrome is an autoimmune, demyelinating neuropathy mediated through toll-like receptor 4 activation by bacterial lipo-oligosaccharides.6 Although the pathogenesis is incompletely understood, prior C jejuni infection is considered a major risk factor.6 Similarly, an association between growth of Campylobacter spp on culture of fecal samples and development of acute polyradiculoneuritis has been identified in dogs fed raw chicken.7 Bacteremia develops in approximately 0.15% of human enteric cases, typically secondary to immunosuppression.8 Campylobacteriosis-associated abortion in humans is extremely rare, but has been described in association with suppurative placentitis.9
In veterinary species, C jejuni infection is best known as a cause of late-term abortion in sheep, but it can also cause abortions in cattle, goats, and dogs and has been identified in poultry.10,11 Historically, Campylobacter fetus subsp fetus was considered the main species that causes ovine abortion.12 However, since the 1980s, C jejuni has replaced C fetus subsp fetus as the most common cause of ovine abortion in the United States.13 This shift in species prevalence is attributed to the selection of a highly virulent and tetracycline-resistant strain of C jejuni.13,14
Among pregnant ewes infected with C jejuni, abortions may occur at any stage of pregnancy; other outcomes include stillborn, unthrifty, or clinically normal lambs.15 Rarely, metritis leads to maternal death. The primary route of infection is oral, and the major sources include fecal material and fetal tissues.1,16 A multidrug efflux pump of C jejuni, CmeABC, is upregulated in the presence of bile, which is essential for intestinal colonization by the organism and contributes to the antimicrobial resistance of C jejuni.17 Uterine localization of infection is probably a chance outcome of short-term bacteremia in immunologically naïve sheep.12,16 Although C jejuni is considered a normal gastrointestinal and biliary commensal in sheep, factors such as pregnancy-associated immunosuppression and exposure of naïve sheep to new strains of the organism may predispose ewes to development of bacteremia.11 Campylobacter jejuni-associated neonatal losses are usually sporadic, but abortion rates in exposed sheep flocks can reach 50% with various lesions including placentitis and fetal edema, bronchopneumonia, and multifocal hepatic necrosis.18
The differential diagnoses for gross foci of hepatic necrosis in aborted or perinatal sheep include Flexispira rappini infection and necrobacillary hepatitis of umbilical origin (ie, focal hepatitis following omphalitis), the latter of which is caused by Fusobacterium necrophorum.11 Definitive diagnosis of abortion induced by C jejuni infection requires identification of the organism by PCR assay or culture from samples of fetal abomasal contents or fetal membranes, lungs, or liver.15 Because C jejuni can be a normal gastrointestinal and biliary commensal, positive test results must be interpreted in light of the dam's clinical history, fetal lesions, and tissues tested. Treatment of affected ewes generally includes administration of antimicrobials, such as cephalosporins or tetracyclines. Preventive measures (eg, efflux-pump inhibitor probiotic treatment17,19) are designed to reduce the bacterial burden on farms. It is important to note the public health risk of contact with sheep during or after abortion because many ovine abortifacient pathogens are zoonotic.
Footnotes
Bruker BiotyperIII, version 3.1.66, Bruker, Billerica, Mass.
References
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