A pmp genes-based PCR as a valuable tool for the diagnosis of avian chlamydiosis

Prevalence and Genotyping of Chlamydia psittaci from Domestic Waterfowl, Companion Birds, and Wild Birds in Taiwan

Chlamydia psittaci, the causative agent of avian chlamydiosis, an important zoonotic disease, infects a wide range of birds. Infected birds, whether symptomatic or asymptomatic, intermittently shed the agent through respiratory and intestinal routes. Therefore, it is essential to investigate the epizootiology of C. psittaci in poultry, pet birds, and wild birds. In this study, cloacal or fecal swabs collected from domestic waterfowl, psittacine birds, Columbidae, and wild birds were used to determine the prevalence of C. psittaci in Taiwan between 2014 and 2017. The C. psittaci infection rate was as high as 34.2% among domestic waterfowl farms. The waterfowl isolates clustered into two groups based on ompA phylogeny: one group (G1-like) clustered with the Polish G1 strains; the other group (waterfowl-TW) clustered near, but independently from, the classical ABE genotype cluster. Separately, 3.1% of parrot samples tested positive for C. psittaci belonging to genotype A. C. psittaci isolates of genotype B were detected in 10.1% of racing pigeons and other Columbidae. Wild bird samples from a wildlife refuge had a 2.2% prevalence rate; among these, two atypical C. psittaci genotypes were detected in samples from a Malayan night heron (Gorsachius melanolophus) and a Taiwan barbet (Megalaima nuchalis). Taken together, our results revealed that the risk of C. psittaci transmission from domestic waterfowl and Columbidae birds to humans could be underestimated, given the high prevalence rates in these birds. Furthermore, the free-range rearing system of waterfowl in Taiwan may promote C. psittaci transmission between poultry and wild birds. Pet birds and racing pigeons, which are in close contact with people, are also possible sources for cross-species transmission. Further studies are necessary to elucidate the virulence, biological and genetic characteristics, and modes of transmission of Taiwanese C. psittaci isolates to facilitate the prevention and control of C. psittaci infection.

Evolution, phylogeny, and molecular epidemiology of Chlamydia

The Chlamydiaceae are a family of obligate intracellular bacteria characterized by a unique biphasic developmental cycle. It encompasses the single genus Chlamydia, which involves nine species that affect a wide range of vertebral hosts, causing infections with serious impact on human health (mainly due to Chlamydia trachomatis infections) and on farming and veterinary industries. It is believed that Chlamydiales originated ∼700mya, whereas C. trachomatis likely split from the other Chlamydiaceae during the last 6mya. This corresponds to the emergence of modern human lineages, with the first descriptions of chlamydial infections as ancient as four millennia. Chlamydiaceae have undergone a massive genome reduction, on behalf of the deletional bias "use it or lose it", stabilizing at 1-1.2Mb and keeping a striking genome synteny. Their phylogeny reveals species segregation according to biological properties, with huge differences in terms of host range, tissue tropism, and disease outcomes. Genome differences rely on the occurrence of mutations in the >700 orthologous genes, as well as on events of recombination, gene loss, inversion, and paralogous expansion, affecting both a hypervariable region named the plasticity zone, and genes essentially encoding polymorphic and transmembrane head membrane proteins, type III secretion effectors and some metabolic pathways. Procedures for molecular typing are still not consensual but have allowed the knowledge of molecular epidemiology patterns for some species as well as the identification of outbreaks and emergence of successful clones for C. trachomatis. This manuscript intends to provide a comprehensive review on the evolution, phylogeny, and molecular epidemiology of Chlamydia.

Chlamydophila species in dairy farms: polymerase chain reaction prevalence, disease association, and risk factors identified in a cross-sectional study in western Germany

The prevalence of Chlamydophila spp. was determined in a cross-sectional study carried out in 2007 using 100 randomly selected dairy herds in the western part of Germany. Ten dairy cows per herd were sampled in herds with fewer than 100 cows; in bigger herds, 10% of the cows were sampled. For the detection of Chlamydophila spp., vaginal swabs from early lactating dairy cows were analyzed using an established highly sensitive genus-specific real-time PCR. In consideration of the discontinuous shedding of the pathogen, a herd was classified as positive if at least 1 animal per herd tested positive for Chlamydophila spp. By use of these methods and definitions, 61% of the dairy herds and 13.5% of the cows were detected as PCR-positive for Chlamydophila spp., which is indicative for ongoing infections. To compare herd health and herd performance between herds testing positive or negative and to identify risk factors for the presence of Chlamydophila spp., a questionnaire was designed to evaluate farm characteristics and management practices. In addition, the performance recordings of the state dairy recording organization were used for these purposes. Milk yield, number of lactations, and calving to first-service interval were lower in herds testing positive for Chlamydophila spp. compared with negative herds. For all these variables, there was no interaction between Chlamydophila status and lactation number. Replacement of animals from outside sources, use of breeding bulls, lack of separate calving pens, and low scores for cleanliness of beddings, walkways, and cows were identified as the main risk factors for Chlamydophila spp.

Recent developments in the laboratory diagnosis of chlamydial infections

There are two main approaches to diagnosing infections by Chlamydia and Chlamydophila spp. in mammals and birds. The first involves the direct detection of the agent in tissue or swab samples, while the second involves the serological screening of blood samples for the presence of anti-chlamydial antibodies. Ultimately, the test that is used is dependent on the types of samples that are submitted to the diagnostic laboratory for analysis. The present paper gives an overview on methodologies and technologies used currently in diagnosis of chlamydial infections with emphasis on recently developed tests. The performance characteristics of individual methods, such as the detection of antigen in smears and in pathological samples, the isolation of the pathogen, various antibody detection tests and DNA-based methods utilising conventional and real-time PCR, as well as DNA microarray technology are assessed, and specific advantages and drawbacks are discussed. Further, a combination of a specific real-time PCR assay and a microarray test for chlamydiae is proposed as an alternative reference standard to isolation by cell culture.