Chlamydiosis in commercial ducks

A recombinase polymerase amplification-based assay for rapid detection of Chlamydia psittaci

Chlamydia psittaci is a zoonotic agent of systemic wasting disease in birds and atypical pneumonia in mammalians including humans, constituting a public health risk. A rapid diagnostic assay would be beneficial in screening C. psittaci in the field. In this study, we developed a probe-based recombinase polymerase amplification (RPA) assay for the rapid detection of C. psittaci. The specific primer pairs and probe targeting the conserved region of the outer membrane protein A gene were designed and applied to the real-time real-time RPA assay. The test can be performed at 39°C for 20 min using a portable device, with sensitivities approaching 100 copies of DNA molecules per reaction, with no cross-reaction with other pathogens. The clinical performance of the RPA assay was evaluated in an outbreak of C. psittaci and has high accuracy levels in field applications. The epidemic C. psittaci strains were classed into 2 genotypes: A and C. Collectively, this study offers a promising approach in screening for C. psittaci both in a laboratory setting and in field settings, and RPA can be used as an effective clinical test to monitor outbreaks in domestic fowl populations.

A parrot-type Chlamydia psittaci strain is in association with egg production drop in laying ducks

Chlamydophila psittaci (C. psittaci) is an avian pathogen associated with systemic wasting disease in birds, as well as a public health risk. Although duck-related cases of psittacosis have been reported, the pathogenicity and shedding status of C. psittaci in ducks are unclear. In this study, we reported that C. psittaci (genotype A) is responsible for a disease outbreak characterized by poor laying performance and severe lesions in multiple organs of ducks. Oral administration of antibiotic, doxycycline, was found to effectively control the C. psittaci infection in laying ducks. Collectively, our new findings provide evidence that C. psittaci was the major pathogen responsible for the outbreak of this disease in ducks. In order to reduce economic losses incurred by this disease, effective control measures must be taken to prevent infection in laying duck farms.

Chlamydia psittaci in ducks: a hidden health risk for poultry workers

Chlamydia psittaci is a zoonotic pathogen associated primarily with avian chlamydiosis also referred as psittacosis. Human psittacosis can lead to severe cases of respiratory disease. The mule duck is one of the main bird hybrids associated with human cases of psittacosis in France. In order to better understand the epidemiology of avian chlamydiosis, monitoring studies were performed in both breeder flocks and mule duck flocks. Surveys conducted in one professional duck bredding organization revealed little shedding in breeder flocks, whereas heavy but asymptomatic C. psittaci shedding was observed in most of the mule duck flocks, mostly when birds were reared in open range conditions on farms. Human cases of psittacosis linked to duck breeder flocks and their progeny led to detection of heavy shedders in all the suspected flocks despite no birds showing clinical signs. Offspring of one of the infected female flocks was analyzed and also proved to be infected by C. psittaci. Field studies suggest that C. psittaci infections in duck farms involve horizontal and probably vertical transmission but that the environment also plays an important role in maintaining infection on farms. In the light of the widespread occurrence of C. psittaci on duck farms, it has become urgent to clearly identify sources of contamination in order to take appropriate field management measures to minimize worker exposure.

Zoonotic Chlamydophila psittaci infections from a clinical perspective

Human psittacosis is a zoonotic infectious disease which is caused by the obligate intracellular bacterium Chlamydophila psittaci. Transmission of the disease usually originates from close contact with infected birds, most frequently in the context of the poultry industry, and from contact with Psittaciformes (cockatoos, parrots, parakeets and lories). Due to a low awareness of the disease and a variable clinical presentation psittacosis is often not recognised as such by general practitioners. This review therefore gives an overview of the epidemiology, symptoms, diagnosis and possible treatments for psittacosis in humans. The current case definition for epidemiological surveillance, as issued by the CDC, is discussed, as well as the possible emergence of Cp. psittaci antibiotic-resistant strains. There is an urgent need for information and for awareness campaigns directed at professional health care workers and the general public. In addition, a broader use of new diagnostic methods in medical laboratories and the development of prophylactics are called for.

Chlamydial infections in duck farms associated with human cases of psittacosis in France

Five severe cases of psittacosis in individuals associated with duck farms were notified in France between January and March 2006. Diagnostic examination included serology and/or molecular detection by PCR from respiratory samples. As a consequence, we investigated all duck flocks (n=11) that were housed in the three farms where human infections occurred. While serology by complement fixation test was negative for all samples, cloacal and/or tracheal chlamydial excretion was detected by PCR in all three units. Notably, one duck flock was tested strongly positive in 2 of the 3 affected farms, and Chlamydophila (C.) psittaci strains were isolated from cloacal and/or tracheal swab samples from both farms. Human samples and duck isolates exhibited the same PCR-RFLP restriction pattern, which appeared to be an intermediate between genotypes A and B. Analysis of ompA gene sequences and comparison to those of the type strains showed that the isolates could not be strictly assigned to any of the generally accepted genotypes of C. psittaci. Further analysis by MLVA of the PCR-positive human samples revealed two distinct patterns, which were related to previously isolated C. psittaci duck strains.

Chlamydophila psittaci infections in birds: a review with emphasis on zoonotic consequences

The first part of the present review gives an overview on the history of infectious agents of the order Chlamydiales and the general infection biology of Chlamydophila (C.) psittaci, the causative agent of psittacosis. In the second part, the classification of C. psittaci strains, as well as issues of epidemiology of avian chlamydiosis., disease transmission routes, clinical disease, public health significance, present legislation and recommendations for prevention and control are reviewed.

Construction and immunogenicity of recombinant adenovirus expressing the major outer membrane protein (MOMP) of Chlamydophila psittaci in chicks

Avian chlamydiosis is caused by Chlamydophila psittaci. The major outer membrane protein (MOMP) encoded by the outer membrane protein 1 (omp1) gene is an excellent candidate for genetic engineering of a vaccine against avian chlamydiosis. In this study, the MOMP gene was amplified by PCR and cloned into the transfer vector pShuttle-CMV. The recombinant plasmid was obtained by recombination between the plasmid pShuttle-CMV-MOMP and skeleton vector pAdEasy-1 in Escherichia coli strain BJ5183. The titer of recombinant adenovirus containing the MOMP gene (rAd-MOMP) of C. psittaci was 3.4x10(10)TCID(50)/ml in human embryonic kidney 293 (HEK293) monolayer cells. The expression of the MOMP in HEK293 cells infected with rAd-MOMP was confirmed by an indirect immunofluorescence assay. Specific pathogen free (SPF) chicks were inoculated with 10(6), 10(8), and 10(10)TCID(50) of rAd-MOMP/chick. Inoculated chicks generated antibodies against MOMP of C. psittaci, which were detected by an indirect hemagglutination test (IHA). The vaccinated chicks were challenged with a virulent Chinese field isolate. Nine out of 10 chicks in the vaccinated group were protected, while birds in the wild-type adenovirus control group and the PBS control group all showed clinical signs after challenge. The results indicate that the recombinant adenovirus containing the MOMP gene of C. psittaci might be a candidate vaccine against avian chlamydiosis.

Methods of detection of Chlamydia psittaci in domesticated and wild birds

OBJECTIVE

To study the occurrence of Chlamydia psittaci in domesticated and wild birds and compare the sensitivity of molecular detection with cell culture isolation.

DESIGN

Study of cell culture isolation and PCR detection of C psittaci in avian samples.

PROCEDURE

Samples were obtained from 485 birds. Domesticated birds were selected at random from pet shops, private aviaries and zoos, while wild birds were captured locally, sampled, and immediately released. Swabs were collected from choanal slit, conjunctiva and cloaca of each bird and pooled. Samples were divided into equal portions for use in PCR dot-blot and cell culture detection. PCR and dot-blot detection was based on the ompB gene.

RESULTS

Prevalence of infection varied markedly between flocks of captive birds. It was highest where there were frequent changes in the flock members or where there were many birds confined in small areas. C psittaci was not detected in wild birds or water birds. The sensitivity of cell culture compared to PCR dot-blot detection was 68%. All samples positive by cell culture were also positive by PCR.

CONCLUSIONS

PCR-dot blot detection of C psittaci in birds appears to be more sensitive than cell culture isolation in this study. C psittaci infection of birds may occur in clinically normal captive birds.

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.

Chlamydiosis in workers at a duck farm and processing plant

An outbreak of chlamydiosis was investigated in workers at a duck farm and processing plant during winter 1989. Chlamydia psittaci was isolated from ducks, but there was little evidence of clinical chlamydiosis in the ducks. Serological tests showed that 76% of workers had been exposed to infection, 12% recently, 16% had not been exposed and 8% had inconclusive test results. There was a strong association (P < 0.05) between years of employment and exposure to infection. Infection appeared to be contracted during the first year of employment. Measures were implemented to reduce shed contamination and control rodents and wild birds. At the same time, ducks were medicated, the processing plant was modified, work practices were altered and workers were advised about chlamydiosis to reduce the risk of human infection.