Identification of the 1B vaccine strain of Chlamydia abortus in aborted placentas during the investigation of toxaemic and systemic disease in sheep.

CASE HISTORY: One hundred and forty Cheviot and 100 Suffolk cross Mule primiparous 1-2-year-old ewes, from a flock of about 700 ewes, were vaccinated with an attenuated live 1B strain Chlamydia abortus vaccine about 4 weeks before ram introduction (September 2011). Between 08 March and 01 April 2012, 50 2-year-old ewes aborted and 29 of these died, despite antimicrobial and anti-inflammatory treatment and supportive care. PATHOLOGICAL FINDINGS: Seven fetuses and three placentae from five 2-year-old ewes were submitted for pathological investigation. The aborted fetuses showed stages of autolysis ranging from being moderately fresh to putrefaction. Unusual, large multifocal regions of thickened membranes, with a dull red granular surface and moderate amounts of grey-white surface exudate were seen on each of the placentae. Intracellular, magenta-staining, acid fast inclusions were identified in Ziehl Neelsen-stained placental smears. Immunohistochemistry for Chlamydia-specific lipopolysaccharide showed extensive positive labelling of the placental epithelia. LABORATORY FINDINGS: Molecular analyses of the aborted placentae demonstrated the presence of the 1B vaccine-type strain of C. abortus and absence of any wild-type field strain. The vaccine strain bacterial load of the placental tissue samples was consistent with there being an association between vaccination and abortion. DIAGNOSIS: Initial laboratory investigations resulted in a diagnosis of chlamydial abortion. Further investigations led to the identification of the 1B vaccine strain of C. abortus in material from all three of the submitted aborted placentae. CLINICAL RELEVANCE: Timely knowledge and understanding of any potential problems caused by vaccination against C. abortus are prerequisites for sustainable control of chlamydial abortion. This report describes the investigation of an atypical abortion storm in sheep, and describes the identification of the 1B vaccine strain of C. abortus in products of abortion. The significance of this novel putative association between the vaccine strain of C. abortus and severe clinical disease is unknown. Aspects of the approach that is described are relevant to the investigation of all outbreaks of ovine abortion, irrespective of the diagnosis. Awareness of the changing role of C. abortus as a major global cause of abortion ought to reinforce the importance of monitoring of adequate biosecurity in those countries which are currently free from chlamydial abortion.

Cerebral segmental polyarteritis of unknown aetiology in sheep.

Vasculitis affecting the meningeal elastic arteries was identified in six sheep of various breeds during routine diagnostic investigation. The lesions consisted of multifocal intimal proliferation, thickening of the tunica media, multifocal infiltration of the media by inflammatory cells and more extensive perivascular accumulation of lymphocytes and plasma cells within the tunica adventitia. Fibrinoid necrosis affected an intergyral artery in one sheep. Immunohistochemistry failed to demonstrate pestivirus antigen associated with the lesions and no alternative aetiology was defined. Possible causes of meningeal segmental polyarteritis in sheep are discussed.

Acute and chronic gas bubble lesions in cetaceans stranded in the United Kingdom.

The first evidence suggestive of in vivo gas bubble formation in cetacea, including eight animals stranded in the UK, has recently been reported. This article presents the pathologic findings from these eight UK-stranded cetaceans and two additional UK-stranded cetacean cases in detail. Hepatic gas-filled cavitary lesions (0.2-6.0 cm diameter) involving approximately 5-90% of the liver volume were found in four (two juvenile, two adult) Risso's dolphins (Grampus griseus), three (two adult, one juvenile) common dolphins (Delphinus delphis), an adult Blainville's beaked whale (Mesoplodon densirostris), and an adult harbour porpoise (Phocoena phocoena). Histopathologic examination of the seven dolphin cases with gross liver cavities revealed variable degrees of pericavitary fibrosis, microscopic, intrahepatic, spherical, nonstaining cavities (typically 50-750 microm in diameter) consistent with gas emboli within distended portal vessels and sinusoids and associated with hepatic tissue compression, hemorrhages, fibrin/organizing thrombi, and foci of acute hepato-cellular necrosis. Two common dolphins also had multiple and bilateral gross renal cavities (2.0-9.0 mm diameter) that, microscopically, were consistent with acute (n = 2) and chronic (n = 1) arterial gas emboli-induced renal infarcts. Microscopic, bubblelike cavities were also found in mesenteric lymph node (n = 4), adrenal (n = 2), spleen (n = 2), pulmonary associated lymph node (n = 1), posterior cervical lymph node (n = 1), and thyroid (n = 1). No bacterial organisms were isolated from five of six cavitated livers and one of one cavitated kidneys. The etiology and pathogenesis of these lesions are not known, although a decompression-related mechanism involving embolism of intestinal gas or de novo gas bubble (emboli) development derived from tissues supersaturated with nitrogen is suspected.

Chronic meningoencephalitis associated with Brucella sp. infection in live-stranded striped dolphins (Stenella coeruleoalba).

A chronic, non-suppurative meningoencephalitis was found in three young striped dolphins (Stenella coeruleoalba) during routine neuropathological examination of marine mammals live-stranded on the Scottish coast. In all three dolphins the lesions were associated with the isolation of a Brucella sp. from the brain and with the immunohistochemical detection of brucella antigen. Moreover, antibodies to Brucella spp. were detected in the two dolphins that were subjected to serological examination. Immunohistochemical and serological examinations for morbillivirus antigen and antibodies, respectively, were negative in all cases. Although brucella infection of marine mammals has been extensively documented in recent years, its association with lesions and disease is less well recognized. The present report provides the first description of an association between Brucella sp. infection and neuropathological changes in a cetacean species.