Molecular and serological dynamics of Chlamydia pecorum infection in a longitudinal study of prime lamb production

© 2018 Bommana et al. Background. Chlamydia pecorum is a globally significant livestock pathogen causing pathology and production losses. The on-farm infection and serological dynamics and the relevance of existing diagnostic tools for diagnosing C. pecorum in livestock remains poorly characterized. In this study, we characterized the antigen and antibody dynamics of this pathogen in a longitudinal study of prime lamb production, utilizing the infection focused C. pecorum-specific 16S rRNA qPCR assay and serology based chlamydial Complement fixation Test (CFT). Methods. The study consisted of 76 Border Leicester mixed sex lambs (39 females and 37 males) that were sampled bimonthly from 2-10 months of age in a commercial farm operating in Central NSW, Australia. Blood/plasma was analysed for CFT antibodies, and swabs from conjunctival, rectal and vaginal sites were analysed for C. pecorum shedding using qPCR. We assessed the temporal and overall dynamics of C. pecorum in lambs, including detailed description and comparison of qPCR and CFT, the timing of first detection by either diagnostic method, the lag between infection and antibody response; and the distribution of qPCR load and CFT antibody titre over time. Results. Over the study period, C. pecorum was highly prevalent (71.0% by qPCR, 92.1% by CFT, 96.0% by both), with 21.1% (16/76) lambs shedding ≥1;000 qPCR copies/ml (denoted as high shedders). C. pecorum shedding (as evidence of infection) were first observed at two months of age (14.4%) with a significant peak of infection occurring at six months of age (34.2%), whereas seroconversions peaked at eight months of age (81.5%). 52.6% of C. pecorum qPCR and CFT positive lambs became qPCR negative by 10 months of age, indicating clearance of chlamydial infection. Although CFT is utilised for on-farm detection of active infection, we confirm that it lagged behind qPCR detection (average lag 1.7 ± 2.1 months) and that the proportion of qPCR positives simultaneously identified by CFT was low with 2/11 (18.1%), 0/13, 17/25 (68.0%), 5/7 (71.4%) and 1/10 (10.0%) concurrent seroconversions occurring at two, four, six, eight and 10 months of age, respectively. Discussion. This work reveals rapid rates of C. pecorum infection and widespread exposure during lamb production. The comparison of molecular and serological diagnostic agreement longitudinally, supports the use of qPCR as an important ancillary tool for the detection of active infections in conjunction with chlamydial CFT for routine veterinary diagnostics. Development of rapid Point-of-Care (POC) tools for diagnosing active infection would be valuable for producers and veterinarians

Four-Port Microstripline Antenna Integrated With a Distributed Amplifier

In this paper, we propose a 4-port edge-fed rectangular microstripline antenna that is integrated with a 4-FET dual-fed distributed amplifier. The 4-port antenna is directly connected to the FETs and has the additional roles of power combining, harmonic suppression and FET biasing. This approach eliminates transmission lines and other elements that would otherwise be needed to realize the amplifier and connect it to an antenna, thereby saving circuit area and minimizing losses

Understanding the health and production impacts of endemic Chlamydia pecorum infections in lambs

Lamydia pecorum is a globally recognised livestock pathogen that is capable of causing severe and economically significant diseases such as arthritis in sheep and cattle. Relatively little information is available on the clinical progression of disease and the long-term effects of asymptomatic and symptomatic chlamydiosis in sheep. Recent studies in calves indicate that endemic C. pecorum infections may reduce growth rates. To investigate the clinical health parameters and production impacts of endemic C. pecorum infection in an Australian commercial lamb flock, we performed bimonthly sampling and clinical health assessments on 105 Border Leicester lambs from two to ten months of age. Chlamydial status was investigated via serology and species-specific quantitative PCR. Throughout the study period, conjunctivitis remained a persistent clinical feature while signs of arthritis (e.g. palpable synovial joint effusions) resolved in a subset of lambs while persisting in others. Clinical disease and C. pecorum infection were highest at six months of age (weaning). As previously reported, peak seroconversion tends to occur two months after the onset of clinical symptoms (6 months of age), with lambs clearing chlamydial infection by 10 months of age, despite ongoing disease still being present at this time. Notably, the presence of chlamydial infection did not affect lamb mass or growth rates throughout the study. At necropsy, C. pecorum was not detected within the joints of lambs with chronic arthritis. Molecular analysis of the strains in this flock suggest that the infecting strains circulating in this flock are clonal C. pecorum pathotypes, denoted ST 23, commonly associated with conjunctivitis and polyarthritis in Australian sheep. This study provides a platform for further research in the epidemiology and disease transmission dynamics of C. pecorum infections in sheep

The limitations of commercial serological assays for detection of chlamydial infections in Australian livestock

Chlamydia pecorumand Chlamydia abortus are related ruminant pathogens endemic to different global regions. Potential co-infections combined with the lack of species-specific serological assays challenge accurate diagnosis. Serological screening revealed low C. abortus seropositivity with the peptide-based ELISA (1/84; 1.2%) in Australian sheep yet moderate seropositivity in a Swiss flock with history of C. abortus-associated abortions (17/63; 26.9%). By whole cell antigen complement fixation tests (CFT) and ELISA, chlamydial seropositivity was significantly higher in all groups, suggesting cross-reactivity between these two chlamydial species and non-specificity of the tests. However, only C. pecorum DNA could be detected by qPCR in Chlamydia seropositive Australian animals screened, suggesting chlamydial seropositivity was due to cross-reactivity with endemic C. pecorum infections. These results suggest ascribing Chlamydia seropositivity to chlamydial species in livestock using whole-cell antigen CFT or ELISA should be treated with caution; and that peptide-based ELISA and qPCR provide greater chlamydial species-specificity

Safety and immunogenicity of a prototype anti-Chlamydia pecorum recombinant protein vaccine in lambs and pregnant ewes

© 2017 Elsevier Ltd Arthritis and kerato-conjunctivitis caused by Chlamydia pecorum in lambs are difficult to diagnose and treat. We tested the ability of a prototype C. pecorum vaccine (SC-vaccine), comprised of C. pecorum major outer membrane protein (MOMP-G) and polymorphic membrane protein G (PmpG), to trigger a Chlamydia-specific humoral and cell-mediated immune response in lambs and pregnant ewes. Vaccinations with the SC-vaccine (one and two injections) were very well tolerated by all ewes and lambs. Although the overall immune responses of ewes to SC-vaccination was poor, their lambs showed stronger antigen-specific immune response than lambs from control vaccine ewes. SC-vaccination in lambs triggered production of systemic anti-MOMP-G and anti-PmpG IgG antibodies and secretory IgA in the ocular mucosa. Double vaccination caused statistically significant increases in the height and duration of the humoral response. Antigen-specific IFN-γ was produced in the peripheral blood mononuclear cells of vaccinated lambs

Radiofrequency ablation of drug refractory ventricular tachycardia related to cocaine use: A feasibility, safety, and efficacy study

RF Ablation of VT in Chronic Cocaine Users Background Cocaine use is a known but rare cause of cardiac arrhythmias. Ventricular arrhythmias related to cocaine may not respond to antiarrhythmic drugs and may need treatment with radiofrequency ablation. Objectives We describe the clinical and electrophysiological characteristics of cocaine-related ventricular tachycardia (VT) from a multicenter registry. Methods Subjects presenting with VT related to cocaine use and being considered for radiofrequency ablation have been included in the study. Patients who were refractory to maximal medical therapy underwent radiofrequency ablation of the VT. Clinical, procedural variables, efficacy, and safety outcomes were assessed. Results A total of 14 subjects met study criteria (age 44 ± 13, range 18- to 68-year-old with 79% male, 71% Caucasian). MRI showed evidence of scar only in 43% of patients (6/14). The mechanism of VT was focal in 50% (n = 7) and scar related reentry in 50% (n = 7) based on 3D mapping. The mean VT cycle length was 429 ± 96 milliseconds. The site of origin was epicardial in 16% (3/18) of VTs. Most clinical VTs were hemodynamically stable (75%). Mean ejection fraction at the time of admission was 44 ± 14%. Duration of procedure was 289 ± 50 minutes. One subject developed pericardial tamponade requiring drainage. At 18 ± 11 months follow-up, freedom from arrhythmia was seen in 86% (1 case lost to follow-up and 2 died). Conclusion Radiofrequency ablation is not only feasible but also safe and effective in patients who have drug refractory VT related to chronic cocaine use. © 2014 Wiley Periodicals, Inc