A comprehensive review on avian chlamydiosis: a neglected zoonotic disease

Abstract

Avian chlamydiosis is one of the important neglected diseases with critical zoonotic potential. Chlamydia psittaci , the causative agent, affects most categories of birds, livestock, companion animals, and humans. It has many obscured characters and epidemiological dimensions, which makes it unique among other bacterial agents. Recent reports on transmission from equine to humans alarmed the public health authorities, and it necessitates the importance of routine screening of this infectious disease. High prevalence of spill-over infection in equines was associated with reproductive losses. Newer avian chlamydial species are being reported in the recent years. It is a potential biological warfare agent and the disease is an occupational hazard mainly to custom officers handling exotic birds. Prevalence of the disease in wild birds, pet birds, and poultry causes economic losses to the poultry industry and the pet bird trade. Interestingly, there are speculations on the ‘legal’ and ‘illegal’ bird trade that may be the global source of some of the most virulent strains of this pathogen. The mortality rate generally ranges from 5 to 40% in untreated cases, but it can sometimes be higher in co-infection. The intracellular lifestyle of this pathogen makes the diagnosis more complicated and there is also lack of accurate diagnostics. Resistance to antibiotics is reported only in some pathogens of the Chlamydiaceae family, but routine screening may assess the actual situation in all pathogens. Due to the diverse nature of the pathogen, the organism necessitates the One Health partnerships to have complete understanding. The present review focuses on the zoonotic aspects of avian chlamydiosis with its new insights into the pathogenesis, transmission, treatment, prevention, and control strategies. The review also briefs on the basic understandings and complex epidemiology of avian chlamydiosis, highlighting the need for research on emerging one health perspectives.

Metagenomic next‐generation sequencing for the diagnosis of Chlamydia psittaci pneumonia

“…The efficacy of macrolides was not being determined in this study because only one patient received azithromycin combined with doxycycline and moxifloxacin. Tetracyclines are recommended as the first‐line treatment for Chlamydia psittaci pneumonia 28 . Indeed, in this study, patients initially treated with doxycycline on admission responded quickly to treatment as indicated by decreased body temperature, improvement of cough, fatigue, poor appetite, shortness of breath and absorption of pulmonary lesions based on imaging results.…”

Chlamydia Species and Related Risk Factors in Poultry in North-Western Italy: Possible Bird-to-Human Transmission for C. gallinacea

“…C. psittaci, long considered to be the only pathogenic species in birds and aetiological agent of avian chlamydiosis and human psittacosis, is common in poultry farms worldwide [ 9 , 10 ]. The disease severity in birds varies according to host species, age, and immune status as well as to the virulence of the bacterial strain [ 10 , 11 ]. In most cases, C .…”

“…In most cases, C . psittaci outbreaks in poultry may be characterized by mild respiratory symptoms and latent infections with intermittent and recurrent shedding of the pathogen, often leading to chronic clinical forms [ 11 , 12 ]. Since high load of C. psittaci is shed via faeces and nasal discharges, aerosol dissemination and sometimes ingestion of contaminated material are the main routes of chlamydial transmission [ 13 ].…”

“…Other ways of transmission include sharing of contaminated water sources and bloodsucking ectoparasites’ bites; moreover, vertical transmission has been proven in poultry and some wild bird species [ 14 , 15 ]. Thus, birds act as carriers and important reservoirs of infection, posing a potential threat to both other animal species and humans [ 11 , 16 , 17 , 18 ].…”

“…Psittacosis, defined as the human disease caused by C. psittaci zoonotic infection, is an occupational disease, affecting mostly bird handlers, veterinarians, poultry workers, and slaughterhouse workers who are exposed to the highest risk of infection by manipulating or having contact with infected birds and fomites [ 10 ]. Symptoms in humans range from asymptomatic infection to severe and/or systemic disease affecting multiple organ systems with fever, headache, respiratory disease, and other manifestations (including endocarditis, myocarditis, hepatitis, arthritis, conjunctivitis, encephalitis) [ 11 , 19 , 20 ].…”