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Vaccination is the best approach for controlling the spread of chlamydial infections, in animal and human populations. This review summarises the progress that has been made towards the development of effective vaccines over the last 50 years, and discusses current vaccine strategies. The ultimate goal of vaccine research is to develop efficacious vaccines that induce sterile, long-lasting, heterotypic protective immune responses. To date, the greatest success has been in developing whole organism based killed of live attenuated vaccines against the animal pathogens Chlamydophila abortus and Chlamydophila felis. However, similar approaches have proved unsuccessful in combating human chlamydial infections. More recently, emphasis has been placed on the development of subunit of multi-component vaccines, as cheaper, safer and more stable alternatives. Central to this is a need to identify candidate vaccine antigens, which is being aided by the sequencing of representative genomes of all of the chlamydial species. In addition, it is necessary to identify suitable adjuvants and develop methods for antigen delivery that are capable of eliciting mucosal and systemic cellular and humoral immune responses. DNA vaccination in particular holds much promise, particularly in terms of safety and stability, although it has so far been less effective in humans and large animals than in mice. Thus, much research still needs to be done to improve the delivery of plasmid DNA, as well as the expression and presentation of antigens to ensure that effective immune responses are induced. [ABSTRACT FROM AUTHOR]

Comments on a study on the role of Chlamydophila spp. in bovine upper respiratory tract disease. Species that have reported to infect cattle; Link between a high seroprevalence of anti-chlamydial antibodies and diseases in cattle; Implication of the research findings.

Highlights • Wave of abortions in a vaccinated sheep flock. • Detection of C. abortus by real time PCR in vaginal swabs from aborted ewes and in tissues collected from dead fetuses. • Identification of the vaccine strain using the PCR-HRM typing tool. • WGS of one isolate identified the 10 SNP vaccine specific markers. Abstract Chlamydia abortus is responsible for enzootic abortion (known as ovine enzootic abortion (OEA) and enzootic abortion of ewes (EAE)) in both sheep and goats and has major economic implications for the farming industry worldwide. A virulence-attenuated mutant strain of C. abortus (strain 1B) is currently commercially available as a live attenuated vaccine for immunization of sheep and goats in several European countries. Following an abortion storm in a French flock of 200 ewes that occurred two years after vaccination of 36 replacement ewes with the commercial 1B vaccine strain, the vaginal swabs of 3 vaccinated and 7 unvaccinated aborted ewes and 12 of the 13 dead fetuses were found to be positive for C. abortus by real-time PCR. Genotyping of the samples, using vaccine-specific SNP markers, identified all as positive for the vaccine-type strain. The recent vaccination of this flock with the attenuated commercial vaccine strain, the large number of abortion cases observed in ewes irrespective of vaccination status, the high C. abortus load detected in vaginal swabs or abortion tissues and the identification of specific vaccine-type markers in these samples strongly suggest that the 1B strain has been transmitted from vaccinated to naïve animals, thus mimicking a natural wild-type infection. [ABSTRACT FROM AUTHOR]

Porcine proliferative enteropathy (PPE) caused by the bacterium Lawsonia intracellularis causes considerable economic loss to the pig industry. The objective of this study was to evaluate the seroprevalence of L. intracellularis exposure in different age groups of pigs (growers to finishers) within English farms and to identify potential risk factors. Samples were obtained in a cross-sectional study of 147 farms between 2008 and 2009. Twelve samples (six growers and six finishers) from each farm were tested for L. intracellularis by antibody ELISA. At animal level there was a significant positive linear trend between seroprevalence and age in weeks (r² = 2.65, P < 0.001), with seroprevalence lowest (24.73%) at 11 weeks and highest (93.33%) at 24 weeks. At farm level, seroprevalence was significantly lower in growers than finishers (56.80% vs. 94.26%, P < 0.001). Farms reporting minor Salmonella problems and those that brought boars onto the farm had higher odds of testing positive in growers (OR 5.69 and 4.31, respectively. On the other hand, farms where producers considered temperature as an important stress factor (OR = 0.3) and which had more than two sites on which pigs are kept (OR = 0.16) were less likely to test positive in growers. The current study confirmed the high prevalence of L. intracellularis in English pig farms. The potential risk factors and further information of the disease impact on the farm productivity will aid the development of appropriate control strategies through better understanding of the disease. [ABSTRACT FROM AUTHOR]

Abstract: Chlamydophila (C.) abortus is a major cause of infectious abortion in sheep in many countries. Twenty-one pregnant sheep were experimentally infected intranasally with C. abortus at 70 days of gestation (dg). Thereafter, a number of animals were killed at weekly intervals and a post-mortem examination was carried out. Evidence of chlamydial infection in the placenta was determined by isolation of the bacterium by tissue culture and detection of C. abortus DNA by real-time polymerase chain reaction (real-time PCR). In addition, histopathological changes in the placenta were assessed, as was the detection of chlamydial antigen by immunohistochemistry (IHC). Evidence of placental infection was observed as early as 2 weeks after inoculation, and while only relatively low numbers of bacteria were isolated by culture and/or detected by real-time PCR prior to 113–114dg, at 119–121dg, it was more numerous. This study, using the four criteria for assessment of infection, showed that while C. abortus gained access to the placenta as early as 85dg, characteristic histopathological changes were not apparent until 119/121dg. While the chronology of when the bacterium arrived in the placenta and subsequent lesion development is remarkable for its consistency this paper provides more reliable data on the former which in turn now allows study of the factors that permit its access to this tissue and govern its multiplication and the ensuing triggering of damage. [Copyright &y& Elsevier]