Laboratory methods for case finding in human psittacosis outbreaks: a systematic review

Abstract

BackgroundPsittacosis outbreak investigations require rapid identification of cases in order to trace possible sources and perform public health risk assessments. In recent outbreaks in the Netherlands, such investigations were hampered by the non-specificity of laboratory testing methods to identify human Chlamydia psittaci infections.MethodA systematic search of PubMed and Scopus databases of literature published between 01 January, 1986 and 03 July, 2017 was done to find best practices of laboratory-testing methods used in psittacosis outbreaks of two or more human cases. Reference lists of included articles were hand searched to identify additional articles.ResultsThirty-seven eligible articles were identified, describing 44 human psittacosis outbreaks in 12 countries. Laboratory tests performed were PCR (with various targets), serologic tests (complement binding reactions, ELISA’s, immunofluorescence tests and immuno-peroxidase tests) and culture, in various combinations. The literature provided no ‘gold standard’ laboratory testing strategy to identify recent human C. psittaci infections. In most psittacosis outbreaks, for a considerable number of cases (or tested individuals in an exposed cohort), C. psittaci infection could not be confirmed, nor excluded as causative pathogen. None of the testing strategies was found to be suitable for (nearly) full case finding.ConclusionPCR enables rapid identification of human psittacosis patients and helps source finding by genotyping but has the disadvantage that sensitivity is high only in the acute phase. In outbreak situations, there is often a time delay and therefore, there is a need for new serologic testing methods next to PCR, with good specificity and sensitivity. Moreover, serum is easier to collect than the preferred diagnostic materials for PCR. A serologic test that can reliably confirm infection status without the necessity of convalescent serum sampling would enhance case finding, source tracing, identification of risk factors and assessment of burden of disease in various settings.Electronic supplementary materialThe online version of this article (10.1186/s12879-018-3317-0) contains supplementary material, which is available to authorized users.

Animal sources for zoonotic transmission of psittacosis: a systematic review

“…We maintained the number of cases as stated in the original article, because some articles did not mention a case definition, and other articles differed too much in sampling methods and type of test to distinguish between case definitions. This broad range of tests and criteria for case confirmations is in line with the main findings of a review by Nieuwenhuizen et al on laboratory methods for case finding in human psittacosis outbreaks [14]. They concluded that there is no standard or uniformity in tests used to confirm human cases.…”

“…In 1985, an outbreak of psittacosis affected employees at a duck processing plant in the United Kingdom [6]. Nowadays psittacosis cases are usually limited to local outbreaks, small clusters or isolated cases [7][8][9][10][11][12][13][14][15][16][17]. Community-acquired pneumonia (CAP) is the most important presentation of human psittacosis, but microbiological testing for psittacosis in a pneumonia patient is often not incorporated in routine diagnostics.…”

The application of metagenomic next-generation sequencing in diagnosing Chlamydia psittaci pneumonia: a report of five cases

“…Serological tests are only appropriate for retrospective diagnosis because sera from the both acute and convalescent phase of the illness are required [9]. PCR-based testing is the most specific and fastest method but only sensitive in the acute phases of the infection [2]. The current case series indicated that mNGS could be used to diagnose Chlamydia psittaci infection.…”

“…Chlamydia psittaci is an obligatory intra-cellular Gramnegative bacterium that typically infects birds, but could occasionally cause psittacosis in humans when contaminated aerosols from infected birds are inhaled. Chlamydia psittaci pneumonia in humans is underestimated due to low awareness of the disease and atypical clinical presentation in majority of the cases [1][2][3]. The low sensitivity and complex procedure of Chlamydia psittaci culture causes it hardly routinely performed in most diagnostic laboratories.…”

“…The low sensitivity and complex procedure of Chlamydia psittaci culture causes it hardly routinely performed in most diagnostic laboratories. Other laboratory testing included serological assay and polymerase chain reaction (PCR) based methods, but both have questionable sensitivity and specificity [2]. Untargeted metagenomic nextgeneration sequencing (mNGS) has been increasingly used in the diagnosis of infectious diseases, particularly when conventional diagnostic approaches have limitations [4].…”