Psittacosis (infection with Chlamydia psittaci) can have diverse presentations in humans, ranging from asymptomatic infection to severe systemic disease. Awareness of psittacosis and its presentations are low among clinicians and the general public. Therefore, underdiagnosis and thereby underestimation of the incidence and public health importance of psittacosis is very likely. We used the methodology developed for the Burden of communicable diseases in Europe toolkit of the European Centre for Disease Prevention and Control, to construct a model to estimate disease burden in disability-adjusted life years (DALYs) attributable to psittacosis. Using this model, we estimated the disease burden caused by psittacosis in the Netherlands to have been 222 DALY per year (95% CI 172–280) over the period 2012–2014. This is comparable with the amount of DALYs estimated to be due to rubella or shigellosis in the same period in the Netherlands. Our results highlight the public health importance of psittacosis and identify evidence gaps pertaining to the clinical presentations and prognosis of this disease.

Psittacosis is a zoonotic infectious disease caused by the transmission of the bacterium Chlamydia psittaci from birds to humans. Infections in humans mainly present as community-acquired pneumonia (CAP). However, most cases of CAP are treated without diagnostic testing, and the importance of C. psittaci infection as a cause of CAP is therefore unclear. In this meta-analysis of published CAP-aetiological studies, we estimate the proportion of CAP caused by C. psittaci infection. The databases MEDLINE and Embase were systematically searched for relevant studies published from 1986 onwards. Only studies that consisted of 100 patients or more were included. In total, 57 studies were selected for the meta-analysis. C. psittaci was the causative pathogen in 1·03% (95% CI 0·79–1·30) of all CAP cases from the included studies combined, with a range between studies from 0 to 6·7%. For burden of disease estimates, it is a reasonable assumption that 1% of incident cases of CAP are caused by psittacosis.

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.

Chlamydia (C.) psittaci, formerly known as Chlamydophila psittaci infections cause important economical losses to the poultry industry and are a danger to public health. The economic and zoonotic impact of C. psittaci infections in the Western poultry industry is well documented. Less is known on its occurrence in Asia. In the following review we address C. psittaci infections in Chinese poultry in view of China supplying 40.8% of global egg production and 14.2, 69.3 and 91.1% of global chicken, duck and goose meat, respectively. The current paper compiles English and Chinese scientific literature on C. psittaci infections in Chinese poultry. The paper is focusing on seroprevalence, culture, direct antigen detection, molecular characterisation, observed symptoms, Chinese traditional medicine and psittacosis case reports. A review on the epidemiology of chlamydiosis in Chinese poultry clearly illustrates the widespread presence of virulent C. psittaci strains in chickens, ducks and geese across China. In Western countries, C. psittaci infections in poultry are principally treated with antibiotics. In China, however, herbal medicine is often used in conjunction with antibiotic treatment or as prophylaxis. The applied production and marketing systems facilitate zoonotic transfer. Chinese occupationally acquired psittacosis cases include reports on infections contracted from ducks, pigeons, chickens and peacocks.

Ornithosis outbreaks in poultry processing plants are well-described, but evidence for preventive measures is currently lacking. This study describes a case-control study into an outbreak of ornithosis at a poultry processing plant in the East of England, identified following three employees being admitted to hospital. Workers at the affected plant were recruited via their employer, with exposures assessed using a self-completed questionnaire. Cases were ascertained using serological methods or direct antigen detection in sputum. 63/225 (28%) staff participated, with 10% of participants showing evidence of recent infection. Exposure to the killing/defeathering and automated evisceration areas, and contact with viscera or blood were the main risk factors for infection. Personal protective equipment (goggles and FFP3 masks) reduced the effect of exposure to risk areas and to self-contamination with potentially infectious material. Our study provides some evidence of effectiveness for respiratory protective equipment in poultry processing plants where there is a known and current risk of ornithosis. Further studies are required to confirm this tentative finding, but in the meantime respiratory protective equipment is recommended as a precautionary measure in plants where outbreaks of ornithosis occur.

In December 2008, three hospitalized cases of suspected psittacosis infection were notified by respiratory disease clinicians from a local hospital to the Regional Epidemiology Unit of Pays de la Loire, France. They all had attended a bird fair. A retrospective cohort study was conducted among exhibitors and organizers to identify potential risk factors in relation to this fair. Environmental and veterinary investigations were implemented to trace potential sources of infection. We identified two confirmed, two probable and 44 possible cases among participants. The attack rate in exhibitors and organizers was 38% (33/86). The median incubation period was 11 days (range 6–22 days). Individuals located in two particular sectors of the showroom were found to be at double the risk of developing psittacosis (relative rate 2·1, 95% confidence interval 1·03–4·18) than those in other sectors. Pooled faecal samples of birds belonging to a possible case exhibitor tested positive for Chlamydiaceae by PCR. Ventilation conditions in the showroom were inadequate. This investigation allowed the formulation of recommendations to prevent psittacosis in bird exhibitions which are held weekly in France.