Chlamydia in cases of cattle pneumonia in Scotland

Indication of spatially random occurrence of Chlamydia-like organisms in Bufo bufo tadpoles from ponds located in the Geneva metropolitan area

Occurrence of bacteria belonging to the order Chlamydiales was investigated for the first time in common toad (Bufo bufo) tadpole populations collected from 41 ponds in the Geneva metropolitan area, Switzerland. A Chlamydiales-specific real-time PCR was used to detect and amplify the Chlamydiales 16S ribosomal RNA–encoding gene from the tails of 375 tadpoles. We found the studied amphibian populations to host Chlamydia-like organisms (CLOs) attributable to the genera Similichlamydia, Neochlamydia, Protochlamydia and Parachlamydia (all belonging to the family Parachlamydiaceae), Simkania (family Simkaniaceae) and Estrella (family Criblamydiaceae); additionally, DNA from the genus Thermoanaerobacter (family Thermoanaerobacteriaceae) was detected. Global autocorrelation analysis did not reveal a spatial structure in the observed CLOs occurrence rates, and association tests involving land cover characteristics did not evidence any clear effect on CLOs occurrence rates in B. bufo. Although preliminary, these results suggest a random and ubiquitous distribution of CLOs in the environment, which would support the biogeographical expectation ‘everything is everywhere’ for the concerned microorganisms.

A Review on Chlamydial Diseases in Animals: Still a Challenge for Pathologists?

Chlamydiae have a worldwide distribution causing a wide range of diseases in human hosts, livestock, and companion animals as well as in wildlife and exotic species. Moreover, they can persist in their hosts as asymptomatic infections for extended periods of time. The introduction of molecular techniques has revolutionized the Chlamydia field by expanding the host range of known chlamydial species but also by discovering new species and even new families of bacteria in the broader order Chlamydiales. The wide range of hosts, diseases, and tissues affected by chlamydiae complicate the diagnosis such that standard diagnostic approaches for these bacteria are rare. Bacteria of the Chlamydiales order are small and their inclusions are difficult to detect by standard microscopy. With the exception of avian and ovine chlamydiosis, macroscopic and/or histologic changes might not be pathognomic or indicative for a chlamydial infection or even not present at all. Moreover, detection of chlamydial DNA in specimens in the absence of other methods or related pathological lesions questions the significance of such findings. The pathogenic potential of the majority of recently identified Chlamydia-related bacteria remains largely unknown and awaits investigation through experimental or natural infection models including histomorphological characterization of associated lesions. This review aims to summarize the historical background and the most important developments in the field of animal chlamydial research in the past 5 years with a special focus on pathology. It will summarize the current nomenclature, present critical thoughts about diagnostics, and give an update on chlamydial infections in domesticated animals such as livestock, companion animals and birds, as well as free-ranging and captive wild animals such as reptiles, fish, and marsupials.

Culture-independent genomics of a novel chlamydial pathogen of fish provides new insight into host-specific adaptations utilized by these intracellular bacteria

Several Chlamydiales families are associated with epitheliocystis, a common condition of the fish gill epithelium. These families share common ancestors with the Chlamydiaceae and environmental Chlamydiae. Due to the lack of culture systems, little is known about the biology of these chlamydial fish pathogens. We investigated epitheliocystis in cultured Orange-spotted grouper (Epinephelus coioides) from North Queensland, Australia. Basophilic inclusions were present in the gills of 22/31 fish and the presence of the chlamydial pathogen in the cysts was confirmed by in situ hybridization. Giant grouper (Epinephelus lanceolatus) cultured in the same systems were epitheliocystis free. 16S rRNA gene sequencing revealed a novel member of the Candidatus Parilichlamydiaceae: Ca. Similichlamydia epinephelii. Using metagenomic approaches, we obtained an estimated 68% of the chlamydial genome, revealing that this novel chlamydial pathogen shares a number of key pathogenic hallmarks with the Chlamydiaceae, including an intact Type III Secretion system and several chlamydial virulence factors. This provides additional evidence that these pathogenic mechanisms were acquired early in the evolution of this unique bacterial phylum. The identification and genomic characterization of Ca. S. epinephelii provides new opportunities to study the biology of distantly-related chlamydial pathogens while shining a new light on the evolution of pathogenicity of the Chlamydiaceae.

Effect of Parachlamydia acanthamoebae on pulmonary function parameters in a bovine respiratory model

The aim of this study was to evaluate pulmonary dysfunction induced by experimental infection with Parachlamydia acanthamoebae in calves. Intrabronchial inoculation with P. acanthamoebae was performed in 31 calves aged 2-3 months old at two different challenge doses of 10(8) and 10(10) inclusion-forming units (IFU) per animal. Control animals received heat inactivated bacteria. The effects on pulmonary gas exchange were determined by arterial blood gas analysis and haemoximetry during the 7 days post inoculation (DPI). For pulmonary function testing (PFT), impulse oscillometry, capnography, and measurement of O2 uptake were undertaken in spontaneously breathing animals 7 and 3 days before inoculation and were repeated until 10 DPI. In the early phase after challenge (1-3 DPI), mild hypoxaemia occurred, which was accompanied by a significant reduction in both tidal and alveolar volumes (each related to bodyweight, BW). In parallel, expiratory flow rate and specific ventilation (i.e. minute ventilation related to O2 uptake) were significantly increased. Minute and alveolar ventilations (each related to metabolic BW) increased significantly due to higher respiratory rates, lasting until 4 and 5 DPI, respectively. Oxygen uptake was slightly reduced during the first 2 days after challenge, but increased significantly during the recovery phase, from 4 to 8 DPI. No deterioration in respiratory mechanics or acid-base balance was observed. Respiratory infection with 10(10) IFU P. acanthamoebae per calf induced mild respiratory dysfunction, mainly characterised by hypoxaemia. The study's findings do not indicate severe pathophysiological consequences of P. acanthamoebae infection on pulmonary function in the bovine host.

Chlamydia pecorum infections in sheep and cattle: A common and under-recognised infectious disease with significant impact on animal health

There is a growing recognition that infections of livestock by the obligate intracellular bacterium, Chlamydia pecorum, are more widespread than was previously thought. A range of diseases have been associated with this pathogen, with the most important manifestations including infectious arthritis, infertility, enteritis, reduced growth rates, mastitis, and pneumonia. C. pecorum infections have also been associated with sub-clinical disease, highlighting our lack of knowledge about its true economic impact on livestock producers. Diagnosis of C. pecorum infection is based on clinical findings, serology and histopathology, which are not necessarily implemented in subclinical or early stages of infection, thus potentially contributing to under-diagnosis and under-reporting of infections associated with this bacterium. Recent molecular epidemiology studies have revealed that C. pecorum is genetically diverse and that there may be an association between certain strains and disease in sheep and cattle. Antimicrobial treatment of affected animals has questionable efficacy, justifying development of chlamydia vaccines for livestock. This review summarises current knowledge of the prevalence and impact of C. pecorum infections in sheep and cattle and provides an update on attempts to improve detection, management and treatment of infections by this important obligate intracellular pathogen.

A bovine model of a respiratory Parachlamydia acanthamoebae infection

The aim of this study was to evaluate the pathogenicity of Parachlamydia (P.) acanthamoebae as a potential agent of lower respiratory tract disease in a bovine model of induced lung infection. Intrabronchial inoculation with P. acanthamoebae was performed in healthy calves aged 2-3 months using two challenge doses: 10(8) and 10(10) bacteria per animal. Controls received 10(8) heat-inactivated bacteria. Challenge with 10(8) viable Parachlamydia resulted in a mild degree of general indisposition, whereas 10(10) bacteria induced a more severe respiratory illness becoming apparent 1-2 days post inoculation (dpi), affecting 9/9 (100%) animals and lasting for 6 days. The extent of macroscopic pulmonary lesions was as high as 6.6 (6.0)% [median (range)] of lung tissue at 2-4 dpi and correlated with parachlamydial genomic copy numbers detected by PCR, and with bacterial load estimated by immunohistochemistry in lung tissue. Clinical outcome, acute phase reactants, pathological findings and bacterial load exhibited an initial dose-dependent effect on severity. Animals fully recovered from clinical signs of respiratory disease within 5 days. The bovine lung was shown to be moderately susceptible to P. acanthamoebae, exhibiting a transient pneumonic inflammation after intrabronchial challenge. Further studies are warranted to determine the precise pathophysiologic pathways of host-pathogen interaction.

Twenty years of research into Chlamydia-like organisms: a revolution in our understanding of the biology and pathogenicity of members of the phylum Chlamydiae

Chlamydiae are obligate intracellular bacteria that share a unique but remarkably conserved biphasic developmental cycle that relies on a eukaryotic host cell for survival. Although the phylum was originally thought to only contain one family, the Chlamydiaceae, a total of nine families are now recognized. These so-called Chlamydia-like organisms (CLOs) are also referred to as 'environmental chlamydiae', as many were initially isolated from environmental sources. However, these organisms are also emerging pathogens, as many, such as Parachlamydia sp., Simkania sp. and Waddlia sp., have been associated with human disease, and others, such as Piscichlamydia sp. and Parilichlamydia sp., have been documented in association with diseases in animals. Their strict intracellular nature and the requirement for cell culture have been a confounding factor in characterizing the biology and pathogenicity of CLOs. Nevertheless, the genomes of seven CLO species have now been sequenced, providing new information on their potential ability to adapt to a wide range of hosts. As new isolation and diagnostic methods advance, we are able to further explore the richness of this phylum with further research likely to help define the true pathogenic potential of the CLOs while also providing insight into the origins of the 'traditional' chlamydiae.

Molecular and pathological insights into Chlamydia pecorum-associated sporadic bovine encephalomyelitis (SBE) in Western Australia

Background

Despite its global recognition as a ruminant pathogen, cases of Chlamydia pecorum infection in Australian livestock are poorly documented. In this report, a C. pecorum specific Multi Locus Sequence Analysis scheme was used to characterise the C. pecorum strains implicated in two cases of sporadic bovine encephalomyelitis confirmed by necropsy, histopathology and immunohistochemistry. This report provides the first molecular evidence for the presence of mixed infections of C. pecorum strains in Australian cattle.

Case presentation

Affected animals were two markedly depressed, dehydrated and blind calves, 12 and 16 weeks old. The calves were euthanized and necropsied. In one calf, a severe fibrinous polyserositis was noted with excess joint fluid in all joints whereas in the other, no significant lesions were seen. No gross abnormalities were noted in the brain of either calf. Histopathological lesions seen in both calves included: multifocal, severe, subacute meningoencephalitis with vasculitis, fibrinocellular thrombosis and malacia; diffuse, mild, acute interstitial pneumonia; and diffuse, subacute epicarditis, severe in the calf with gross serositis. Immunohistochemical labelling of chlamydial antigen in brain, spleen and lung from the two affected calves and brain from two archived cases, localised the antigen to the cytoplasm of endothelium, mesothelium and macrophages. C. pecorum specific qPCR, showed dissemination of the pathogen to multiple organs. Phylogenetic comparisons with other C. pecorum bovine strains from Australia, Europe and the USA revealed the presence of two genetically distinct sequence types (ST). The predominant ST detected in the brain, heart, lung and liver of both calves was identical to the C. pecorum ST previously described in cases of SBE. A second ST detected in an ileal tissue sample from one of the calves, clustered with previously typed faecal bovine isolates.

Conclusion

This report provides the first data to suggest that identical C. pecorum STs may be associated with SBE in geographically separated countries and that these may be distinct from those found in the gastrointestinal tract. This report provides a platform for further investigations into SBE and for understanding the genetic relationships that exist between C. pecorum strains detected in association with other infectious diseases in livestock.