Evaluation of five immunoassays for detection of Chlamydia psittaci in cloacal and conjunctival specimens from turkeys

Prevalence of New and Established Avian Chlamydial Species in Humans and Their Psittacine Pet Birds in Belgium

The presence and zoonotic transfer of four different avian Chlamydia spp. was assessed in an epidemiological study in a psittacine bird population and its owners. Fecal swabs from 84 pet birds and pharyngeal swabs from 22 bird owners were collected from 21 locations in Flanders. Samples were examined using established and novel PCR platforms combined with culture on PCR-positive samples. Chlamydiaceae DNA was detected in 33 of 84 (39.3%) birds. The predominant part of the avian infections could be attributed to C. psittaci (22 of 84; 26.2%), followed by C. avium (11 of 84; 13.1%). C. gallinacea and C. abortus were not detected in birds or humans. C. psittaci was the only species detected in pet bird owners (4 of 22; 18.2%), stressing its zoonotic importance. This study showed that C. psittaci and the more recently discovered novel avian species C. avium are undoubtedly present in the Flemish psittacine bird population. Our results justify additional research in a larger psittacine bird population and its owners, focusing on C. psittaci and C. avium. In the meantime, increased awareness among pet bird owners and the implementation of preventive measures in the pet bird industry is advised to limit the circulation of established and novel emerging avian chlamydial species.

Prevalence of Chlamydia in Pigs in China from 1985 to 2020: A Systematic Review and Meta-Analysis

Chlamydia is a small gram-negative (G-) microorganism that can be dangerous to human and animals. In this study, we conducted a systematic review and meta-analysis of Chlamydia infection in swine in China. From PubMed, ScienceDirect, Chinese Web of knowledge (CNKI), VIP Chinese journal database, and Wanfang database, we collected a total of 72 publications reported in 1985-2020. The prevalence of Chlamydia was 22.48% in China. In the sampling year subgroup, the prevalence after 2011 was the highest (26.14%). In southern China, the prevalence was 30.97%. By contrast, the prevalence in northern China was only 10.79%. Also the difference was significant (p < 0.05). In the provincial level, Hubei had the highest rate of 36.23%. Boars had a higher prevalence (29.47%). The prevalence of Chlamydia detection in pigs with reproductive disorders (21.86%) was higher than that without reproductive disorders. Among the three age groups, finishing pigs (21.43%) had the highest prevalence. The prevalence in large-scale farmed pigs (28.58%) was the highest in the subgroup of feeding methods. The prevalence in farms was 24.29%, which was the highest in the survey areas. The prevalence in spring was the highest with 40.51%. Other methods had the highest prevalence (39.61%) than enzyme-linked immunosorbent assay (ELISA) and indirect hemagglutination assay. The prevalence of Chlamydia psittaci 18.41% was lower than the prevalence of Chlamydia abortus (41.35%). We also analyzed the impact of different climate factor subgroups (rainfall, temperature, and humidity) on the probability of pigs suffering from the disease. The results showed that Chlamydia was widespread in pigs in China. We suggest that we should strengthen the detection of Chlamydia in the semen of breeding pigs and pigs with reproductive disorders, and reasonably control the environment of large-scale pig farms, so as to reduce further infection of Chlamydia in pigs.

Managing a cluster outbreak of psittacosis in Belgium linked to a pet shop visit in The Netherlands

In July 2013, a Belgian couple were admitted to hospital because of pneumonia. Medical history revealed contact with birds. Eleven days earlier, they had purchased a lovebird in a pet shop in The Netherlands. The bird became ill, with respiratory symptoms. The couple's daughter who accompanied them to the pet shop, reported similar symptoms, but was travelling abroad. On the suspicion of psittacosis, pharyngeal swabs from the couple were taken and sent to the Belgian reference laboratory for psittacosis. Culture and nested polymerase chain reaction (PCR) tests were positive for the presence of Chlamydia psittaci, and ompA genotyping indicated genotype A in both patients. The patients were treated with doxycycline and the daughter started quinolone therapy; all three recovered promptly. Psittacosis is a notifiable disease in Belgium and therefore local healthcare authorities were informed. They contacted their Dutch colleagues, who visited the pet shop. Seven pooled faecal samples were taken and analysed using PCR by the Dutch national reference laboratory for notifiable animal diseases for the presence of Chlamydia psittaci. Four (57%) samples tested positive, genotyping revealed genotype A. Enquiring about exposure to pet birds is essential when patients present with pneumonia. Reporting to health authorities, even across borders, is warranted to prevent further spread.

Emerging Chlamydia psittaci infections in chickens and examination of transmission to humans

Chlamydia psittaci and atypical Chlamydiaceae infections are (re)-emerging in chickens. We therefore examined the prevalence of C. psittaci, atypical Chlamydiaceae and their zoonotic transmission on 19 Belgian chicken farms. Atypical Chlamydiaceae were not detected in chickens but 18 out of 19 farms were positive for C. psittaci by culture and PCR. C. psittaci ompA genotypes A and D were discovered. None of the examined humans (n = 31) was infected with atypical Chlamydiaceae, but 29 (93.5%) of them were positive for C. psittaci by culture and PCR. Genotypes A, D and a mixed infection with genotypes C and D were found. Humans (n = 2) working at the C. psittaci-negative farm never had respiratory complaints, while 25 out of 29 positive farmers (86.2%) reported yearly medical complaints potentially related to psittacosis. Four of them currently experienced respiratory disease and one of them was being treated with antibiotics. Four farmers (12.5%) mentioned that they had pneumonia after starting to keep chickens. Occupational physicians should be aware of emerging Chlamydiaceae infections in chickens.

Emerging Chlamydia psittaci infections in the chicken industry and pathology of Chlamydia psittaci genotype B and D strains in specific pathogen free chickens

Sera of 30 Belgian and 10 Northern French chicken farms were tested by a Chlamydia (C.) psittaci major outer membrane protein (MOMP) based ELISA. Ninety-six percent, 93% and 90% of the Belgian broilers, broiler breeders and layers were seropositive. Ninety-one percent of the French broilers were seropositive. In addition, tissues of 5 Belgian and 5 French broiler farms were examined at slaughter. All French farms were culture positive while C. psittaci was cultured from the lungs of 80% of examined Belgian farms. C. psittaci infections are apparently emerging in chickens raised in Belgium and Northern France. We could proof Hill-Evans postulates for chicken-derived C. psittaci genotype B and D strains. Chicken-processing plant employees should be considered a risk group for human psittacosis. There is a need for higher awareness and for efficient risk assessment and management of C. psittaci infections in chickens as chlamydiosis in broilers seems to be underdiagnosed and infections with highly virulent strains do occur.

Comparison of antigen detection and quantitative PCR in the detection of chlamydial infection in koalas (Phascolarctos cinereus)

The gold standard method for detecting chlamydial infection in domestic and wild animals is PCR, but the technique is not suited to testing animals in the field when a rapid diagnosis is frequently required. The objective of this study was to compare the results of a commercially available enzyme immunoassay test for Chlamydia against a quantitative Chlamydia pecorum-specific PCR performed on swabs collected from the conjunctival sac, nasal cavity and urogenital sinuses of naturally infected koalas (Phascolarctos cinereus). The level of agreement for positive results between the two assays was low (43.2%). The immunoassay detection cut-off was determined as approximately 400 C. pecorum copies, indicating that the test was sufficiently sensitive to be used for the rapid diagnosis of active chlamydial infections.

Zoonotic transmission of Chlamydia psittaci in a chicken and turkey hatchery

Chlamydia psittaci is an obligately intracellular Gram-negative bacterium causing respiratory disease (chlamydiosis) or asymptomatic carriage in birds. C. psittaci is a zoonotic agent causing psittacosis or parrot fever in humans. Vertical and/or horizontal transmission via eggs might have serious repercussions on the C. psittaci infection status of poultry flocks and thus on zoonotic risk for all workers along the poultry supply chain. We therefore studied the presence of C. psittaci in a hatchery. In addition, we examined all (n = 4) employees of the hatchery to evaluate the zoonotic risk. We could not detect C. psittaci on either eggshells or eggshell membranes. However, C. psittaci isolates of different outer-membrane protein A (ompA) genotypes were cultured from the air of both turkey (genotypes A and C) and chicken (genotype D) hatching chambers. Zoonotic transmission occurred in all employees and a mixed infection with up to three different genotypes (A, D and C), also found in air samples, was discovered. Diagnostic monitoring and reporting of C. psittaci infections in poultry workers should be promoted. Additionally, an efficient veterinary vaccine and information campaigns on zoonotic risk and preventive measures against C. psittaci transmission would be beneficial to public health.

Detection of bacterial and viral organisms from the conjunctiva of cats with conjunctivitis and upper respiratory tract disease

A variety of pathogens are involved in conjunctivitis in cats. In this study, the prevalence of feline herpesvirus (FHV), Chlamydophila felis, mycoplasmas, and aerobic bacteria on the conjunctival surface of cats with conjunctivitis and upper respiratory tract disease was investigated by polymerase chain reaction (PCR), immunofluorescent assay (IFA), and aerobic bacterial culture of ocular swabs. Forty-one cats were included of which 37 were found to be infected with an ocular organism. Single and multiple infections were present in 15 and 22 cats, respectively. FHV, mycoplasmas, and C felis were detected by PCR in 11 (27%), 20 (49%), and 23 (56%) cats, respectively. IFA detected 10 cats as positive for C felis. Mycoplasma felis, Mycoplasma canadense, Mycoplasma cynos, Mycoplasma gateae, Mycoplasma lipophilum, and Mycoplasma hyopharyngis were identified by genetic sequencing. The most common aerobic bacteria cultured included Staphylococcus species, Streptococcus species and Micrococcus species. The prevalence of mycoplasmas in cats with conjunctivitis was higher than previously reported, and four of the Mycoplasma species have not been described in cats so far.

Chlamydophila psittaci zoonotic risk assessment in a chicken and turkey slaughterhouse

Chlamydophila psittaci causes respiratory disease in poultry and can be transmitted to humans. We conducted a C. psittaci zoonotic risk assessment study of a chicken and turkey slaughterhouse. Eighty-five percent of the slaughtered chicken flocks tested positive by PCR and culture. Genotype D was discovered. Fifty-seven percent of the slaughtered turkey flocks tested positive by PCR and culture. Genotype D was present. For the chicken slaughterhouse employees, 7.5% and 6% tested positive for C. psittaci by PCR and culture, respectively. In the turkey slaughterhouse, 87% and 61% of the employees tested positive by PCR and culture, respectively. All genotyped human samples contained genotype D. Using stationary bioaerosol monitoring by means of an MAS-100 ecosampler and ChlamyTrap collection medium, chlamydial DNA, and viable organisms were detected in both the chicken and turkey slaughterhouses. Positive air samples were most frequently found in the animal reception area and evisceration room. Zoonotic transmissions were very common, especially from processed turkeys. Accurate diagnostic monitoring and reporting of C. psittaci infections should be promoted in poultry workers.

Biology and intracellular pathogenesis of high or low virulent Chlamydophila psittaci strains in chicken macrophages

Within a few days post infection of SPF turkeys, highly pathogenic Chlamydophila (Cp.) psittaci genotype A and D strains can be found in blood monocytes/macrophages, while this effect is less pronounced for infection with a milder genotype B strain. To elucidate on the observed difference, we studied the developmental cycle of avian Cp. psittaci strains of varying virulence in a matched avian monocyte/macrophage cell line (HD11) by electron microscopy and immunofluorescence and determined the gene transcription of 26 Type III secretion related genes and six control genes upon infection of HD11 cells. The genotype A (84/55) and D (92/1293) strains (1) clearly induced actin recruitment to the site of entry, (2) initiated host cell degeneration at earlier time points, and (3) survived and proliferated better when compared to the milder CP3 strain. Strain 84/2334, genetically intermediate between Cp. psittaci and Cp. abortus, did not induce actin recruitment. Limited mRNA transcripts for the cell division genes ftsW and ftsK were in agreement with the observed low replication of Cp. psittaci in these host cells. The results also indicated that genes coding for the structural components of the Type III secretion system were transcribed earlier compared to an infection in epithelial cells. Based on the presented results, we postulate that upon infection of blood monocytes/macrophages, Cp. psittaci deliberately limits its replication and immediately arms itself to infect other cells elsewhere in the host, whilst using the monocytes/macrophages as a quick transport vehicle.

Protection of budgerigars (Melopsittacus undulatus) against Chlamydophila psittaci challenge by DNA vaccination

Plasmid DNA (pcDNA1::MOMP A) expressing the major outer membrane protein (MOMP) of Chlamydophila psittaci genotype A strain 89/1051 has been tested for its ability to induce protective immunity against Cp. psittaci challenge in budgerigars. Eight pairs of male and female budgerigars were housed in eight separate bird cages placed in two negative pressure isolators, four cages per group. All budgerigars were immunised twice intramuscularly with 100 microasmid DNA. Both groups received a primary DNA inoculation at day 0 followed by a booster inoculation 3 weeks later. Group 1 received pcDNA1::MOMP A, while group 2 received the placebo vaccine pcDNA1. Budgerigars were challenged by aerosol 2 weeks following the booster vaccination. The challenge consisted of 10(8) TCID(50) of the homologous Cp. psittaci genotype A strain. Cloacal and pharyngeal swabs of all budgerigars, taken prior to the experimental infection were negative in both PCR and culture. However, all budgerigars showed low pre-existing serum antibody titres. This indicates that animals were previously infected. Nevertheless, DNA immunisation could significantly reduce clinical signs, macroscopic lesions, pharyngeal and cloacal excretion as well as chlamydial replication, even in the presence of pre-existing serum antibodies, as compared to the placebo-vaccinated controls.

Evaluation of bioaerosol sampling techniques for the detection of Chlamydophila psittaci in contaminated air

Chlamydophila (C.) psittaci, a category B bioterrorism agent, causes respiratory disease in birds and psittacosis or parrot fever in man. The disease spreads aerogenically and no vaccines are available for either birds or man. Highly sensitive C. psittaci bioaerosol monitoring methods are unavailable. We evaluated: (1) dry filtration for collecting C. psittaci from contaminated air using different samplers and membrane filters, (2) impingement into different liquid collection media by use of the AGI-30 impinger and the BioSampler and (3) impaction into newly designed C. psittaci media utilizing the MAS-100 aerosol impactor. For personal bioaerosol sampling, we recommend the use of a gelatin filter in combination with the IOM inhalable dust sampler at an airflow rate of 2L/min. This allowed the detection of 10 organisms of C. psittaci by both PCR and culture. For stationary bioaerosol monitoring, sampling 1000L of air in 10min with the MAS-100 impactor and ChlamyTrap 1 impaction medium was most efficient and made it possible to detect 1 and 10 C. psittaci organisms by PCR and culture, respectively. ChlamyTrap 1 in combination with the MAS-100 impactor might also be applicable for bioaerosol monitoring of viruses.

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.

Evaluation of the prophylactic use of ovotransferrin against chlamydiosis in SPF turkeys

Chlamydophila (C.) psittaci infections are highly prevalent in turkeys and the economical and public health importance of these infections has been recognized since 1950. As there are no vaccines, antibiotic treatment (tetracylines, enrofloxacine) is often needed to allow marketing of poultry. In this study, we explored the use of ovotransferrin (ovoTF), a natural anti-microbial protein, in preventing an experimental C. psittaci infection in specific pathogen free (SPF) turkeys. Turkeys were treated with aerosolized ovoTF prior to the infection. Groups 1 and 2 received a single dose of 10 and 5 mg ovoTF per turkey, respectively. Group 3 received a daily dose of 5mg ovoTF per turkey during 12 days. Group 4 served as untreated, infected control group. Turkeys were aerosol infected using 10(6) TCID(50) of the virulent C. psittaci serovar/genotype D strain 92/1293. Birds were monitored (clinical signs, bacterial excretion) during 12 subsequent days before being necropsied. At necropsy, pathology and C. psittaci replication in various tissues was examined. A single dose of 10mg ovoTF and a repeated daily dose of 5mg ovoTF could not prevent the birds from becoming infected with C. psittaci, but they significantly reduced the outcome of the infection. A single dose of 5mg ovoTF had no influence on the outcome of the infection as compared to the non-treated infected controls. Our results demonstrate the anti-chlamydial effect of ovoTF in vivo and present a base for further research on practical applications of ovoTF on turkey farms.

Use of a nested PCR-enzyme immunoassay with an internal control to detect Chlamydophila psittaci in turkeys

Background

Laboratory diagnosis of Chlamydophila psittaci, an important turkey respiratory pathogen, is difficult. To facilitate the diagnosis, a nested PCR-enzyme immunoassay (PCR-EIA) was developed to detect the Cp. psittaci outer membrane protein A (ompA) gene in pharyngeal swabs.

Methods

The fluorescein-biotin labelled PCR products were immobilized on streptavidin-coated microtiter plates and detected with anti-fluorescein peroxidase conjugate and a colorimetric substrate. An internal inhibition control was included to rule out the presence of inhibitors of DNA amplification. The diagnostic value of the ompA nested PCR-EIA in comparison to cell culture and a 16S-rRNA based nested PCR was assessed in pharyngeal turkey swabs from 10 different farms experiencing respiratory disease.

Results

The sensitivity of the nested PCR-EIA was established at 0.1 infection forming units (IFU). Specificity was 100%. The ompA nested PCR-EIA was more sensitive than the 16S-rRNA based nested PCR and isolation, revealing 105 out of 200 (52.5%) positives against 13 and 74 for the latter two tests, respectively. Twenty-nine (23.8%) out of 122 ompA PCR-EIA negatives showed the presence of inhibitors of DNA amplification, although 27 of them became positive after diluting (1/10) the specimens in PCR buffer or after phenol-chloroform extraction and subsequent ethanol precipitation.

Conclusion

The present study stresses the need for an internal control to confirm PCR true-negatives and demonstrates the high prevalence of chlamydiosis in Belgian turkeys and its potential zoonotic risk. The ompA nested PCR-EIA described here is a rapid, highly sensitive and specific diagnostic assay and will help to facilitate the diagnosis of Cp. psittaci infections in both poultry and man.

Detection of Chlamydophila abortus in sheep and goat flocks in southern Italy by PCR using four different primer sets

An epidemiological survey was performed to detect the presence of Chlamydophila (C.) abortus and other members of the order Chlamydiales in ovine and caprine flocks with a history of abortion in southern Italy. Four pairs of primers were compared to evaluate their ability to detect Chlamydiales using purified DNA preparations and tissue samples from aborted foetuses with suspected chlamydial infections. As expected, amplification of DNA of the reference strain C. abortus using primer pairs U23F/23Sigr, 16SF2/23R, CTU/CTL and CpsiA/CpsiB produced fragments of about 600 bp, 585 bp, 1000 bp and 300 bp, respectively. The detection limits of the four PCR tests performed on serial DNA dilutions of the C. abortus reference strain were of 10 pg, 0.1 pg, 0.1 pg and 1 fg of DNA, respectively. The most sensitive amplification of DNA extracted from the organ tissues was obtained with primer pairs CpsiA/CpsiB, which detected Chlamydophila spp. DNA in all infected tissue samples. Only C. abortus was identified during the survey. The presence of this agent was confirmed in 3 out of 27 ovine and caprine flocks included in the survey suggesting that abortion due to C. abortus is uncommon in southern Italy.

Influence of maternal antibodies on Chlamydophila psittaci-specific immune responses in turkeys elicited by naked DNA

Plasmid DNA (pcDNA1::MOMP D) expressing the major outer membrane protein (MOMP) of an avian Chlamydophila psittaci serovar D strain was tested for its ability to induce protective immunity against C. psittaci challenge in the presence of maternal antibodies. A combined parenteral (intramuscular injection) and mucosal route (DNA drops administered to the nares) of DNA inoculation was used. Following pcDNA1::MOMP vaccination, both T helper and B cell memory were primed. However, high maternal antibodies titres affected the induction of vaccine-specific antibody responses as assessed by MOMP-specific antibody levels in enzyme-linked immunosorbent assay (ELISA). Cell-mediated immunity was unaltered as demonstrated by the significantly heightened proliferative responses of peripheral blood lymphocytes (PBL) following vaccination. DNA vaccination could significantly reduce clinical symptoms, pharyngeal and cloacal excretion as well as Chlamydophila replication, even in the presence of maternal antibodies.

Detection of Chlamydia suis from clinical specimens: comparison of PCR, antigen ELISA, and culture

Cell culture is still widely regarded as the gold standard in chlamydial diagnosis despite its well-known limitations in terms of sensitivity. On the other hand, the polymerase chain reaction (PCR) has emerged as a promising alternative because of rapidity and high sensitivity. However, validation of methodologies is required before the issue of standardization can be addressed. In the present study, 109 clinical samples (organ tissue, nasal, and faecal swabs) from pigs experimentally infected with Chlamydia suis were examined by cell culture, nested PCR in the ompA gene region, and two different antigen enzyme-linked immunosorbent assays (ELISAs) in order to compare the diagnostic performance of these methods. Culture and PCR produced the highest proportion of concordant results (kappa coefficient 0.712). Among 99 samples, 34 were positive in both assays, 51 were negative in both assays, 12 culture-negatives were positive in PCR, and only 2 culture-positives were negative in PCR. Thus, the sensitivity and specificity of PCR vs. culture as standard were 94.4% and 81.0%, respectively, whereas the corresponding values for culture vs. PCR as standard were 73.9% and 96.2%, respectively. Both ELISA tests performed considerably weaker. The data underline the potential of PCR as a powerful detection method for chlamydiae.

Protection of turkeys against Chlamydophila psittaci challenge by parenteral and mucosal inoculations and the effect of turkey interferon-gamma on genetic immunization

Plasmid DNA (pcDNA1::MOMP A) expressing the major outer membrane protein of an avian Chlamydophila psittaci serovar A strain was tested for its ability to induce protective immunity against challenge with the same C. psittaci serovar. A combined parenteral (intramuscular injection) and mucosal route (DNA drops administered to the nares) of DNA inoculation was compared to three other, different routes of administration (intramuscular inoculation, DNA drops administered to the nares and aerosol immunization). In addition, the effect of turkey interferon gamma (tIFN-gamma) on intramuscular immunization was evaluated by co-expressing pCIneo::tIFN-gamma. A significant level of protection was observed in turkeys immunized via the combined parenteral/mucosal route, the intramuscular route or by aerosol. Severe clinical signs and lesions were observed in the non-vaccinated control groups, in 80% of turkeys inoculated with a mixture of pcDNA1::MOMP A and pCIneo::tIFN-gamma, and in 60% of turkeys vaccinated with DNA drops administered to the nares. The use of MOMP-based DNA vaccination as a means of preventing severe clinical signs and lesions in a turkey model of C. psittaci infection was demonstrated, as was down-regulation of the immune response by co-expression of tIFN-gamma.

Evaluation of a latex agglutination kit (Virogen Rotatest) for detection of bovine rotavirus in fecal samples

The performance of the Virogen Rotatest latex agglutination test (LAT) was evaluated for detection of bovine rotavirus antigen. Sixty-three fecal samples from diarrheic calves were collected from November 1999 to May 2000 and screened by LAT, the Rotazyme II enzyme-linked immunosorbent assay (ELISA), and virus isolation (VI) followed by an anti-rotavirus fluorescent-antibody (FA) test to detect the presence of group A rotavirus antigen. Of the 63 samples screened by VI-FA, 33 (58%) tested positive for rotavirus antigen. When the results from the LAT were compared to those from VI-FA, the "gold standard" for detection of bovine rotavirus in fecal samples, the sensitivity and specificity were found to be 87.8 and 73.3%, respectively. Latex agglutination compared with ELISA (the reference method) showed 100% sensitivity and 96.3% specificity, and when ELISA was compared with VI, the sensitivity was 84.8% and the specificity was 73.3%. Latex agglutination is easy to perform in a short time and does not require expensive equipment or skilled personnel, and the reagents have long shelf lives. These factors make the LAT suitable and highly efficient for use in a clinical laboratory as a rapid screening test for bovine rotavirus.

Dynamics of the development of Chlamydophila psittaci inclusions in epithelial and fibroblast host cells

The development of Chlamydophila psittaci (formerly Chlamydia psittaci, avian strains) inclusions in fibroblast L-929 and epithelial BGM cell lines was studied along the bacterial growth cycle using a BGM cell-adapted strain in the presence or absence of cycloheximide and cycloheximide + polyethylene glycol. Evolution of the inclusions was determined in terms of their number and size at 24, 30, 36, 48 and 54 h after infection. Significant differences in the chlamydial growth were found between both host cells, throughout the study. Higher numbers of inclusions (P < 0.05) were observed in L cells while larger inclusions (P < 0.01) were found in BGM cells. In both fibroblast and epithelial cells, inclusions showed a significant (P < 0.001) increase in size at the later times studied. Free extracellular chlamydial particles were noticed at 48 and 54 h post-infection (p.i.) in infected L cells, and at 54 h p.i. in BGM cells. Addition of cycloheximide or cycloheximide + polyethylene glycol had no significant effect on the number of inclusions or their size. The results suggest that host cell characteristics and innate compatibility between Chlamydophila strain and host cell are more important than host cell adaptation for the development of the microorganism.

Optimal development of Chlamydophila psittaci in L929 fibroblast and BGM epithelial cells requires the participation of microfilaments and microtubule-motor proteins

The cytoskeleton is involved in several cellular activities, including internalization and transport of foreign particles. Although particular functions to each cytoskeleton component have been described, interactions between those components seem to occur. The involvement of the different host cell cytoskeletal components in uptake and development of Chlamydophila psittaci is incompletely understood. In this study, the participation of the microfilament network along with the kinesin and dynein microtubule motor proteins in the internalization and further development of Chlamydophila psittaci were investigated in L929 fibroblast and BGM epithelial cells. Cytochalasin D disruption of actin filaments, and blockage of the motor proteins through the introduction of monoclonal antibodies into the host cells were carried out, either single or combined, at different moments around bacterial inoculation, and Chlamydophila infectivity determined 24 h post- inoculation by direct immunofluorescence. Our results show that, although Chlamydophila Ipsittaci can make use of both microfilament-dependent and independent entry pathways in both cell types, Chlamydophila internalization and development in the fibroblast cells mainly concerned processes mediated by microfilaments while in the epithelial cells mechanisms that require microtubule motor proteins were the ones predominantly involved. Evidence that mutual participation of the actin and tubulin networks in both host cells are required for optimal growth of Chlamydophila psittaci is also presented.

Development, characterization, and diagnostic applications of monoclonal antibodies against bovine rotavirus

Hybridomas secreting monoclonal antibodies (MAbs) against the Nebraska calf diarrhea strain of bovine rotavirus (BRV) were characterized. Indirect fluorescent-antibody assay, immunodot assay, and immunoprecipitation were used to select hybridomas that produced anti-BRV MAbs. Seven of the MAbs were shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot assay to be reactive with the BRV outer capsid protein, VP7, which has a molecular mass of 37.5 kDa. None of the seven MAbs were reactive with canine rotavirus, bovine coronavirus, or uninfected Madin-Darby bovine kidney cells. Two clones, 8B4 (immunoglobulin G2a [IgG2a]) and 2B11 (IgG1), were found suitable for use in an antigen capture enzyme-linked immunosorbent assay for detecting BRV in bovine fecal samples. Both were subtype A specific (G6 subtype) but did not react with all isolates of BRV group A.

Turkeys are protected from infection with Chlamydia psittaci by plasmid DNA vaccination against the major outer membrane protein

Plasmid DNA expressing the major outer membrane protein (MOMP) of an avian Chlamydia psittaci serovar A strain has been tested for its ability to raise an immune response and induce protection against challenge with the same serovar. A combined parenteral (intramuscular injection) and mucosal route (DNA drops administered to the nares) of DNA inoculation was compared with gene gun-based immunization. The gene gun delivery of pcDNA1/MOMP as well as the intramuscular-intranasal DNA delivery primed both T-helper and B cell memory, although rMOMP-expressing cells did not induce high antibody responses. Evidence for the priming of the memory was provided by the fact that the pcDNA1/MOMP inoculations raised antibodies belonging to the IgG and not IgM isotype. However, in response to challenge only five out of 15 vaccinated turkeys showed four-fold increases in serum IgG after challenge. By contrast, evidence for the priming of T cell memory in response to challenge was found in all vaccinated turkeys, as shown by the significantly heightened proliferative responses of peripheral blood lymphocytes following vaccination. Both immunization methods produced similar serological and lymphocyte proliferative responses. Notwithstanding the immunization method, a significant level of protection was observed in all pcDNA1/MOMP-immunized turkeys. The efficacy of MOMP-based DNA vaccination as a means of preventing severe clinical signs, lesions and chlamydia excretion in a turkey model of C. psittaci infection was demonstrated.

Development of an antigen spot test for detection of coronavirus in bovine fecal samples

We have developed a rapid and sensitive microimmunodot blot assay, the antigen spot test (AST), for the detection of bovine coronavirus (BCV) antigen from neonatal calf fecal samples. The AST procedure can be completed in 3.5 h, whereas the previously reported immunodot blot assays require 10 to 12 h. Ninety-six samples can be tested per membrane, and 10 membranes (960 samples) may be processed by a single technologist in 1 working day. The effects of detergents, oxidizing chemicals, chaotropic agents, and enzyme substrates in improving the sensitivity and signal-to-noise ratio of the AST were studied. Finally, the sensitivity and specificity of AST for the detection of BCV antigen were compared to those of a sandwich enzyme-linked immunosorbant assay (ELISA) and a hemagglutination assay (HA). Of 347 field samples tested by all three methods, 94.2% were positive by AST, 91.4% were positive by ELISA, and 86.7% were positive by HA. The sensitivity of the AST was determined to be 100% compared to the results of the ELISA reference method. The specificity of the AST was 67%, which reflects a lower limit of detection of 10(4) viral particles per ml in a 10% fecal suspension.

Oxidative activity of turkey monocytes, following the inoculation with Chlamydia psittaci

Chemiluminescence (CL) was used to investigate the competence of turkey monocytes to mount a respiratory burst response upon interaction with Chlamydia psittaci. The oxidative activity of purified turkey monocytes, following inoculation with the avian C. psittaci serovar D strain 92/1293, was studied using luminol- and lucigenin-enhanced CL. Purified turkey monocytes were inoculated with C. psittaci at multiplicity of infection (MOI) of approximately 100, 10 and 1. In the presence of luminol, no detectable CL or only a weak CL response was obtained, and if present it increased with increasing MOI. Either sham inoculated monocytes, or monocyte-free control assays supplemented with C. psittaci, gave no detectable luminol-enhanced CL responses. In the lucigenin-enhanced assays, monocytes inoculated with C. psittaci demonstrated an immediate CL peak, the height of which was proportional to the MOI used. Following inoculations at a MOI 1, a faint second peak was observed, when applying high concentrations of lucigenin. Sham inoculated monocytes gave no detectable lucigenin-enhanced CL responses. However, in the presence of lucigenin, the addition of C psittaci to monocyte-free controls also resulted in an immediate CL peak, though no second peak was detected. This immediate lucigenin-dependent CL peak induced by C. psittaci was similar to the one observed in the presence of monocytes, and was not inhibited by superoxide dismutase. We demonstrated that this avian C. psittaci strain induces only a very weak respiratory burst response in turkey monocytes. In contrast, C. psittaci itself elicited an intense non-superoxide mediated lucigenin-dependent CL, indicating that in chlamydial research the detection of superoxide, using lucigenin, should be confirmed with a specific superoxide inhibitor.

Administration of doxycycline hydrochloride via drinking water to turkeys under laboratory and field conditions

A series of experiments were carried out in order to determine doxycycline hydrochloride (DoxHCl) plasma levels in 6-wk-old turkeys medicated via drinking water containing DoxHCl at a concentration of 250 mg/L under laboratory and field conditions. Maximal plasma concentration (Cmax) values of 5.7 (+/-1.0) microgram/mL and 4.9 (+/-1.4) micrograms/mL obtained after DoxHCl administration during 2 and 7 d, respectively, were not significantly different. A significant difference was found between the area under the plasma concentration-time profile, calculated between 0 and 168 h (AUC(0-168)), Cmax, and the minimal plasma concentration (Cmin) values obtained after medication with a DoxHCl solution at a concentration of 250 mg/L (431.9 +/- 96.6 micrograms.h/mL, 4.9 +/- 1.4 micrograms/mL and 0.7 +/- 0.3 microgram/mL) and after medication with a DoxHCl solution at a concentration of 750 mg/L (1,176.5 +/- 201.8 micrograms.h/mL, 12.5 +/- 2.7 micrograms/mL and 2.9 +/- 0.4 micrograms/mL), respectively. The increase in body weight was also significantly higher for turkeys medicated with a DoxHCl solution at a concentration of 750 mg/L (83.7 g/d) than for the lower concentration (35.6 g/d). The DoxHCl solution uptake significantly decreased with the increase of DoxHCl concentration. A Cmax value of 1.7 +/- 0.6 micrograms/mL and a Cmin value of 0.5 +/- 0.1 microgram/mL were observed during the field experiment. Water consumption under laboratory conditions was followed for tap water (70 +/- 50 mL/kg.d) and for a DoxHCl solution at a concentration of 250 mg/L supplemented with 1 g anhydrous citric acid/L (119 +/- 6 mL/kg.d) and revealed to be not significantly different. The variability was significantly higher for tap water than for the DoxHCl solution. The stability of the DoxHCl solution containing 1 g citric acid/L over 24 h was 99% expressed as the percentage of the initial concentration.

The prevalence of Chlamydia psittaci infections in Belgian commercial turkey poults

The prevalence of Chlamydia psittaci infections in Belgian commercial turkey poults was examined and a follow-up study of one Belgian turkey flock was performed. Sera were examined for the presence of anti-chlamydia antibodies by immunoblotting. Cloacal and conjunctival swab smears and lung impression smears were examined for the presence of chlamydial antigen using the IMAGEN Chlamydia immunofluorescence test. Anti-chlamydia antibodies were found in 90 of 100 sera collected at slaughter from turkeys raised during the summer of 1992. The following winter, 73 of 100 sera reacted positively. On all twenty farms examined during 1992, turkeys were positive for anti-chlamydial antibodies. During 1993, chlamydial antigen was detected in swabs from 20 of 40 slaughterhouse turkeys tested. Antigen was found more often in the cloaca than in the conjunctiva. Chlamydial antigen was detected in samples from each of the 4 farms examined. The follow-up study on a turkey farm, sampling the birds at weekly intervals from one week old until 12 weeks of age, revealed that chlamydial antigen and anti-chlamydial antibodies were present during the whole period. During 1994, chlamydial antigen was detected in 45 of 60 lungs from slaughterhouse turkeys from all of 6 farms. During 1995, chlamydial antigen was detected in 41 of 54 lungs of 6 week old commercial turkey poults. The results of the present study indicate that Chlamydia psittaci infections are highly prevalent amongst Belgian commercial turkey poults with apparently little seasonal or year-to-year variation and that turkeys can contract the infection at an early age.

Chlamydia psittaci infections: a review with emphasis on avian chlamydiosis

In the first part of this article the general characteristics of Chlamydia psittaci namely the history, taxonomy, morphology, reproductive cycle, metabolism and genetics are reviewed. For the taxonomy in particular, a considerable amount of new information has become available in recent years, following the application of monoclonal antibodies and restriction enzymes. Using these techniques isolates of Chlamydia psittaci from birds have been subdivided in different serovars, a number of isolates have been classified in a new species (Chlamydia pecorum) and isolates from animals have been classified as Chlamydia trachomatis. In the second part of the article, the current knowledge on avian chlamydiosis is summarized. Emphasis is put on clinical signs, lesions, pathogenesis, epizootiology, immunity, diagnosis, prevention and treatment. Also the public health considerations are reviewed. It is concluded that the diagnosis of avian chlamydiosis is laborious and that there is still a need for more accurate, simple and rapid diagnostic tools, both for antigen and antibody detection in various species of birds.