Genetic diversity of Listeria monocytogenes strains in ruminant abortion and rhombencephalitis cases in comparison with the natural environment.

BACKGROUND: Listeria monocytogenes is the causative agent of listeriosis, a serious disease affecting both animals and humans. Here, multilocus sequence typing (MLST) was used to characterize the genetic diversity of Listeria monocytogenes strains isolated from the natural environment and animal clinical cases in Europe. The prevalence of clonal complexes (CCs) obtained was compared according to (i) the origin of isolation - clinical cases vs. natural environment - and (ii) the clinical form of animal listeriosis - rhombencephalitis vs. abortion. To this aim, two datasets were constructed. The clinical dataset consisted of 350 animal clinical isolates originating from France and Slovenia and supplemented with isolates from Switzerland and Great Britain. The natural environment dataset consisted of 253 isolates from the natural environment originating from Slovenia and supplemented with isolates from nine other European countries. RESULTS: For the clinical cases, CC1, CC4-CC217 and CC412 were the most prevalent in rhombencephalitis and CC1, CC37 and CC4-CC217 in abortion. The hypervirulent CC1 and CC4-CC217 prevailed in both datasets. These results indicated that livestock is constantly exposed to hypervirulent CCs. CC1 was significantly associated with a clinical origin, whereas CC9, CC29 and CC14 were associated with the natural environment. CC1 was predominant among rhombencephalitis cases both in cattle and small ruminants, and its prevalence did not differ significantly between these two groups. A novel association of CC37 and CC6 with abortion cases was revealed. CONCLUSIONS: Here, we show that CC1 and CC4-CC217 are prevalent in isolates of environmental and animal clinical origin, suggesting that ruminants are frequently exposed to hypervirulent CCs. The presence of CC4 in two mastitis cases calls for further attention due to direct threat to the consumer. We showed several associations between CCs and the origin of isolation or clinical form of listeriosis, e.g. CC37 and CC6 with abortion. This study improves our understanding of the population structure of L. monocytogenes isolates from the natural environment and animal clinical cases. Moreover, it provides a basis for future studies aiming to determine the underlying mechanisms of phenotypic traits of interest.

Listeria monocytogenes sequence type 1 is predominant in ruminant rhombencephalitis.

Listeria (L.) monocytogenes is an opportunistic pathogen causing life-threatening infections in diverse mammalian species including humans and ruminants. As little is known on the link between strains and clinicopathological phenotypes, we studied potential strain-associated virulence and organ tropism in L. monocytogenes isolates from well-defined ruminant cases of clinical infections and the farm environment. The phylogeny of isolates and their virulence-associated genes were analyzed by multilocus sequence typing (MLST) and sequence analysis of virulence-associated genes. Additionally, a panel of representative isolates was subjected to in vitro infection assays. Our data suggest the environmental exposure of ruminants to a broad range of strains and yet the strong association of sequence type (ST) 1 from clonal complex (CC) 1 with rhombencephalitis, suggesting increased neurotropism of ST1 in ruminants, which is possibly related to its hypervirulence. This study emphasizes the importance of considering clonal background of L. monocytogenes isolates in surveillance, epidemiological investigation and disease control.

First report and histological features of Chlamydia pecorum encephalitis in calves in New Zealand.

CASE HISTORY: Between September and October 2013, 40 of 150 crossbred Friesian dairy calves on a farm in the Manawatu region of New Zealand developed neurological signs when between 1 and 3 months of age. Calves were grazed in multiple mobs and calves from each mob were affected. A variable response was observed to initial treatment with thiamine, fluoroquinolone antibiotics and non-steroidal anti-inflammatory drugs. CLINICAL AND PATHOLOGICAL FINDINGS: Affected calves exhibited a range of neurological signs that included generalised depression, hind limb ataxia with a stiff gait, and knuckling of the fetlocks. In advanced cases, calves became recumbent with opisthotonous. Over a 4-week period, 13 calves died or were subject to euthanasia and a thorough necropsy was performed on three of these calves. Necropsy findings included fibrinous peritonitis, pleuritis and pericarditis, with no gross abnormalities visible in the brain or joints. Histology of the brain was possible in seven of the affected calves, with lesions ranging from lymphocytic and histiocytic vasculitis and meningoencephalitis, to extensive thrombosis and neutrophilic inflammation. Immunohistochemistry using an anti-chlamydial lipopolysaccharide antibody revealed positive immuno-staining in all seven cases, with no brain samples exhibiting immunostaining for Histophilus somni. DNA was extracted from a sample of fresh brain from one case and chlamydial DNA sequences were amplified by PCR and found to be identical to Chlamydia pecorum. PCR was also performed on formalin-fixed brain tissue from three of the other cases, but no chlamydial DNA was amplified. DIAGNOSIS: Chlamydia pecorum meningoencephalomyelitis (sporadic bovine encephalomyelitis). CLINICAL RELEVANCE: This is the first time that C. pecorum has been confirmed as a cause of clinical disease in New Zealand. Practitioners should be aware of this disease as a differential in calves with neurological signs, and submit samples of formalin-fixed brain as well as fresh brain to enable confirmation of suspected cases using PCR analysis. Furthermore, these cases illustrate that the histological lesions in the brains of calves with C. pecorum are more variable than previously reported, and pathologists should be aware that histological features may overlap with those traditionally ascribed to other organisms, such as H. somni.

Unusual Necrotizing Encephalitis in Raccoons and Skunks Concurrently Infected With Canine Distemper Virus and Sarcocystis sp.

Canine distemper virus commonly infects free-ranging, terrestrial mesopredators throughout the United States. Due to the immunosuppressive effects of the virus, concurrent opportunistic infections are also common. Among these, secondary systemic protozoal infections have been described in a number of species. We report an unusual presentation of necrotizing encephalitis associated withSarcocystissp in four raccoons and one skunk concurrently infected with canine distemper virus. Lesions were characterized by variably sized necrotizing cavitations composed of abundant mineral admixed with inflammatory cells and protozoa.Sarcocystissp was confirmed via immunohistochemistry using a monoclonal antibody toSarcocystis neurona The pathologic changes are similar to lesions in human AIDS patients infected withToxoplasma gondii.

Outbreak of encephalitic listeriosis in red-legged partridges (Alectoris rufa).

An outbreak of neurological disease was investigated in red-legged partridges between 8 and 28 days of age. Clinical signs included torticollis, head tilt and incoordination and over an initial eight day period approximately 30-40 fatalities occurred per day. No significant gross post mortem findings were detected. Histopathological examination of the brain and bacterial cultures followed by partial sequencing confirmed a diagnosis of encephalitis due to Listeria monocytogenes. Further isolates were obtained from follow-up carcasses, environmental samples and pooled tissue samples of newly imported day-old chicks prior to placement on farm. These isolates had the same antibiotic resistance pattern as the isolate of the initial post mortem submission and belonged to the same fluorescent amplified fragment length polymorphism (fAFLP) subtype. This suggested that the isolates were very closely related or identical and that the pathogen had entered the farm with the imported day-old chicks, resulting in disease manifestation in partridges between 8 and 28 days of age. Reports of outbreaks of encephalitic listeriosis in avian species are rare and this is to the best of our knowledge the first reported outbreak in red-legged partridges.