Seroprevalence of Paramyxoviruses in Synanthropic and Semi–Free-Range Birds

Experimental pigeon paramyxovirus-1 infection in chicken: evaluation of infectivity, clinical and pathological manifestations and diagnostic methods

Several pigeon paramyxovirus-1 (PPMV-1) outbreaks in feral pigeons were described recently in Switzerland. The potential of PPMV-1 to induce the notifiable Newcastle disease in chickens is discussed controversially. Therefore, in order to study epidemiologically relevant parameters such as the kinetics of PPMV-1 replication and shedding as well as seroconversion after infection, chickens were infected experimentally with a Swiss PPMV-1 isolate. This generated also defined sample material for the comparison of diagnostic tests. The infectivity of the Swiss PPMV-1 isolate for chickens was demonstrated successfully by virus shedding after experimental inoculation. Our data suggest that long-lasting shedding for up to 60 days can occur in chickens infected with PPMV-1. The isolate used here was of low pathogenicity for chickens. Different quantitative reverse transcription PCR assays were evaluated with a set of Swiss PPMV-1 isolates, and various samples from experimentally infected chickens were analysed with respect to their suitability for viral RNA detection. At 14 days post-infection, virus genome was detected mainly in spleen, caecal tonsils, heart, cloacal swabs, liver, proventriculus, duodenum and kidney tissue samples. Overall, the level of virus replication was low. Not all assays used routinely in diagnostics were capable of detecting viral genome from the isolates tested. Possible explanations are the genetic divergence of PPMV-1 and the low level of viral RNA in the samples. In contrast, two methods that are not used routinely proved more suitable for virus-genome detection. Importantly, the collection of material from various different organs is recommended, in addition to the kidney and brain analysed routinely. In conclusion, this study shows that there is a need to reconsider the type of samples and the protocols used for the detection of PPMV-1 RNA in chickens.

Use of wildlife rehabilitation centres in pathogen surveillance: A case study in white storks (Ciconia ciconia)

More than 70% of new human pathogens are zoonotic and many originate from the wildlife reservoir. Wildlife rehabilitation centres (WRC) are an easily accessible source for sample and data collection for preventive surveillance, but data collected this way may be biased. We use white storks (Ciconia ciconia) as a model to compare pathogen prevalence obtained in the field and WRC. We address factors that may affect disease prevalence data like origin, the age group and the "diseased" state of WRC admissions. In this study we compared prevalence of Escherichia coli and Salmonella spp. in the digestive tract; antibodies against West Nile virus, avian influenza and Newcastle disease virus, and antimicrobial resistance patterns of E. coli between nestling and adult wild storks established in different habitats (n=90) and storks admitted to two different WRC (n=30) in the same region. When age groups and colonies of origin were disregarded, the mean enterobacteria (E. coli, Salmonella) and viral antibody prevalence of the wild population (n=90) were similar to prevalence observed in the individuals admitted to WRC (n=30). However, in fledgling juvenile storks admitted to WRC, the prevalence of Salmonella spp. (13.3%), E. coli showing resistance to cefotaxime (37.9%) and against two antimicrobials at once (41.4%) were more similar to the prevalence in stork nestlings from landfill-associated colonies (7.9%, 37.1% and 48.6%, respectively for prevalence of Salmonella spp. and E. coli displaying, cefotaxime resistance and resistance against two antimicrobials), and significantly higher than in colonies located in natural habitats (0%; 10.5% and 15.8%, respectively). Thus, pathogen surveillance in individuals from an abundant species admitted to WRC is useful to monitor overall mean prevalence, but for certain pathogens may not be sufficient to detect differences between local populations. In addition, the ecology of the tested species and the specific temporal, spatial and age group distribution of WRC admissions have to be taken into account.