Roel Haesendonck

Host Stress Drives Salmonella Recrudescence

Host stress is well known to result in flare-ups of many bacterial, viral and parasitic infections. The mechanism by which host stress is exploited to increase pathogen loads, is poorly understood. Here we show that Salmonella enterica subspecies enterica serovar Typhimurium employs a dedicated mechanism, driven by the scsA gene, to respond to the host stress hormone cortisol. Through this mechanism, cortisol increases Salmonella proliferation inside macrophages, resulting in increased intestinal infection loads in DBA/2J mice. ScsA directs overall Salmonella virulence gene expression under conditions that mimic the intramacrophagic environment of Salmonella, and stimulates the host cytoskeletal alterations that are required for increased Salmonella proliferation inside cortisol exposed macrophages. We thus provide evidence that in a stressed host, the complex interplay between a pathogen and its host endocrine and innate immune system increases intestinal pathogen loads to facilitate pathogen dispersal.

High Seroprevalence of Respiratory Pathogens in Hobby Poultry

SUMMARY Seroprevalence studies on respiratory pathogens have been done extensively in commercial laying hens, broilers, and, to a lesser extent, backyard poultry. In Europe, seroprevalence studies in backyard and fancy breed poultry flocks are scarce and limited to a few pathogens, such as Mycoplasma gallisepticum (MG); others, such as Ornithobacterium rhinotracheale (ORT), are missing. A commercial ELISA for detection of antibodies against six selected pathogens was performed on 460 serum samples from chickens across Flanders. Anti-ORT antibodies were, by far, the most prevalent, with a prevalence of 95.4%. Infectious bronchitis virus, Mycoplasma synoviae, and avian metapneumovirus antibodies were found in 75.6%, 76.3%, and 63.5% of the animals, respectively. Antibodies against MG and infectious laryngotracheitis virus were found in 36.7% and 30% of the animals, respectively. These data demonstrate the high seroprevalence of respiratory pathogens among hobby poultry; therefore, it is possible that this group could act as a reservoir for commercially kept poultry. RESUMEN Nota de investigación- Alta seroprevalencia de patógenos respiratorios en avicultura recreativa. Se han realizado amplios estudios de seroprevalencia de patógenos respiratorios en gallinas de postura, en pollo de engorde comerciales y en menor medida, en aves de traspatio. En Europa, los estudios de seroprevalencia en parvadas de aves de traspatio y en aves de razas finas son escasos y limitados a unos pocos patógenos, como Mycoplasma gallisepticum y no existen disponibles reportes dirigidos a otros patógenos como Ornithobacterium rhinotracheale. Se llevó a cabo un estudio serológico con un estuche comercial de ELISA para la detección de anticuerpos contra seis patógenos seleccionados en 460 muestras de suero de pollos en toda el área de Flandes. Los anticuerpos contra Ornithobacterium rhinotracheale fueron los más frecuentes, con una prevalencia del 95.4%. Los anticuerpos contra el virus de la bronquitis infecciosa, Mycoplasma synoviae, y metapneumovirus aviar se encontraron en 75.6%, 76.3% y 63.5% de los animales, respectivamente. Se encontraron anticuerpos contra el virus de la laringotraqueitis infecciosa y contra Mycoplasma gallisepticum en 36.7% y 30% de los animales, respectivamente. Estos datos demuestran la alta seroprevalencia de patógenos respiratorios en la avicultura recreativa; por lo tanto, es posible que este grupo podría actuar como un reservorio para las aves mantenidas bajo condiciones comerciales.

Feral pigeons: A reservoir of zoonotic Salmonella Enteritidis strains?

Salmonella enterica infections in pigeons are generally associated with pigeon-adapted strains of serovar Typhimurium that are of little public health concern. Here, we isolated Salmonella Enteritidis phage type 4 (PT4), an important human pathogen, from a population of feral pigeons in Brussels, which was further characterized by Pulsed-Field Gel Electrophoresis. All pigeon isolates belonged to the same pulsotype, which has been present in Belgian pigeons at least since 2001 and is associated with poultry and disease in humans. A high prevalence of 33% of Salmonella Enteritidis in Brussels combined with dense pigeon populations suggest that feral pigeons may constitute a significant, but unrevealed reservoir for contracting salmonellosis in the urban environment.

House Sparrows Do Not Constitute a Significant Salmonella Typhimurium Reservoir across Urban Gradients in Flanders, Belgium

In recent decades major declines in urban house sparrow (Passer domesticus) populations have been observed in north-western European cities, whereas suburban and rural house sparrow populations have remained relatively stable or are recovering from previous declines. Differential exposure to avian pathogens known to cause epidemics in house sparrows may in part explain this spatial pattern of declines. Here we investigate the potential effect of urbanization on the development of a bacterial pathogen reservoir in free-ranging house sparrows. This was achieved by comparing the prevalence of Salmonella enterica subspecies enterica serotype Typhimurium in 364 apparently healthy house sparrows captured in urban, suburban and rural regions across Flanders, Belgium between September 2013 and March 2014. In addition 12 dead birds, received from bird rescue centers, were necropsied. The apparent absence of Salmonella Typhimurium in fecal samples of healthy birds, and the identification of only one house sparrow seropositive for Salmonella spp., suggests that during the winter of 2013–2014 these birds did not represent any considerable Salmonella Typhimurium reservoir in Belgium and thus may be considered naïve hosts, susceptible to clinical infection. This susceptibility is demonstrated by the isolation of two different Salmonella Typhimurium strains from two of the deceased house sparrows: one DT99, typically associated with disease in pigeons, and one DT195, previously associated with a passerine decline. The apparent absence (prevalence: <1.3%) of a reservoir in healthy house sparrows and the association of infection with clinical disease suggests that the impact of Salmonella Typhimurium on house sparrows is largely driven by the risk of exogenous exposure to pathogenic Salmonella Typhimurium strains. However, no inference could be made on a causal relationship between Salmonella infection and the observed house sparrow population declines.

Marek's disease virus associated ocular lymphoma in Roulroul partridges (Rollulus rouloul)

Two 1-year old Roulroul partridges (Rollulus rouloul), one male and one female, were presented because of eye problems and anorexia. Twenty of the 30 Roulroul partridges in the owners collection had already died. The affected birds stopped eating, became thinner, and eventually died. Antibiotic treatment, which started because of the suspicion of a septicaemic process, was unsuccessful. At clinical examination of the two partridges it was found that in both birds, one eye ball was filled with a whitish yellow amorphous material and the other eye ball of the female showed a distinct corneal opacity. Both presented birds were euthanized. Necropsy revealed no significant abnormalities in addition to the eye lesions. Histology and immunohistochemistry of the females eye revealed an infiltrate of T-lymphocytes corresponding to ocular lymphoma. Herpesvirus genus-specific PCR, followed by Sanger sequencing confirmed the presumptive diagnosis of Mareks disease in both birds. To our knowledge, this is the first confirmed case of infection with Gallid Herpesvirus 2 (Mareks disease virus) in partridges and the first case in this specific species.

Salmonella Typhimurium DT193 and DT99 are present in great and blue tits in Flanders, Belgium

Endemic infections with the common avian pathogen Salmonella enterica subspecies enterica serovar Typhimurium (Salmonella Typhimurium) may incur a significant cost on the host population. In this study, we determined the potential of endemic Salmonella infections to reduce the reproductive success of blue (Cyanistes caeruleus) and great (Parus major) tits by correlating eggshell infection with reproductive parameters. The fifth egg of each clutch was collected from nest boxes in 19 deciduous forest fragments. Out of the 101 sampled eggs, 7 Salmonella Typhimurium isolates were recovered. The low bacterial prevalence was reflected by a similarly low serological prevalence in the fledglings. In this study with a relatively small sample size, presence of Salmonella did not affect reproductive parameters (egg volume, clutch size, number of nestlings and number of fledglings), nor the health status of the fledglings. However, in order to clarify the impact on health and reproduction a larger number of samples have to be analyzed. Phage typing showed that the isolates belonged to the definitive phage types (DT) 193 and 99, and multi-locus variable number tandem repeat analysis (MLVA) demonstrated a high similarity among the tit isolates, but distinction to human isolates. These findings suggest the presence of passerine-adapted Salmonella strains in free-ranging tit populations with host pathogen co-existence.

The Impact of Deoxynivalenol on Pigeon Health: Occurrence in Feed, Toxicokinetics and Interaction with Salmonellosis.

Seed-based pigeon diets could be expected to result in exposure of pigeons to mycotoxins such as deoxynivalenol (DON). Ingestion of low to moderate contamination levels of DON may impair intestinal health, immune function and/or pathogen fitness, resulting in altered host-pathogen interactions and thus different outcome of infections. Here we demonstrate that DON was one of the most frequently detected mycotoxins in seed-based racing pigeons feed, contaminating 5 out of 10 samples (range 177–1,466 μg/kg). Subsequently, a toxicokinetic analysis revealed a low absolute oral bioavailability (F) of DON in pigeons (30.4%), which is comparable to other avian species. Furthermore, semi-quantitative analysis using high-resolution mass spectrometry revealed that DON-3α-sulphate is the major metabolite of DON in pigeons after intravenous as well as oral administration. Following ingestion of DON contaminated feed, the intestinal epithelial cells are exposed to significant DON concentrations which eventually may affect intestinal translocation and colonization of bacteria. Feeding pigeons a DON contaminated diet resulted in an increased percentage of pigeons shedding Salmonella compared to birds fed control diet, 87 ± 17% versus 74 ± 13%, respectively. However, no impact of DON was observed on the Salmonella induced disease signs, organ lesions, faecal and organ Salmonella counts. The presented risk assessment indicates that pigeons are frequently exposed to mycotoxins such as DON, which can affect the outcome of a Salmonella infection. The increasing number of pigeons shedding Salmonella suggests that DON can promote the spread of the bacterium within pigeon populations.

Comparative population pharmacokinetics and absolute oral bioavailability of COX-2 selective inhibitors celecoxib, mavacoxib and meloxicam in cockatiels (Nymphicus hollandicus)

Selective COX-2 inhibitors are non-steroidal anti-inflammatory drugs which directly target cyclooxygenase-2 (COX-2), an enzyme mainly responsible for induction of inflammation, pyresis and pain. Although commonly used in avian medicine, limited pharmacokinetic (PK) data in domestic and companion birds are available. In this study, PK parameters and absolute oral bioavailability expressed as percentage (F%) of celecoxib (10 mg/kg BW), mavacoxib (4 mg/kg BW) and meloxicam (1 mg/kg BW) were determined following single oral (PO) and intravenous (IV) administration to cockatiels (Nymphicus hollandicus). The drugs were quantified in plasma by liquid chromatography-tandem mass spectrometry. Data were processed using the nonlinear mixed effects (NLME) approach. In contrast to celecoxib (T1/2el = 0.88 h) and meloxicam (T1/2el = 0.90 h), mavacoxib has a prolonged elimination half-life (T1/2el = 135 h) following oral administration of a commercial formulation (CF). High to complete oral absorption was observed following oral administration of celecoxib (F% = 56–110%) and mavacoxib (F% = 111–113%), CF and standard solutions, respectively. In contrast, the F% of meloxicam was low (F% = 11%). Based on the presented results, a less frequent dosing of mavacoxib is proposed compared to celecoxib and meloxicam. However, pharmacodynamic and safety studies are necessary to further investigate the use of these NSAIDs in cockatiels.

Effects of urbanization on host-pathogen interactions, using Yersinia in house sparrows as a model

Urbanization strongly affects biodiversity, altering natural communities and often leading to a reduced species richness. Yet, despite its increasingly recognized importance, how urbanization impacts on the health of individual animals, wildlife populations and on disease ecology remains poorly understood. To test whether, and how, urbanization-driven ecosystem alterations influence pathogen dynamics and avian health, we use house sparrows (Passer domesticus) and Yersinia spp. (pathogenic for passerines) as a case study. Sparrows are granivorous urban exploiters, whose western European populations have declined over the past decades, especially in highly urbanized areas. We sampled 329 house sparrows originating from 36 populations along an urbanization gradient across Flanders (Belgium), and used isolation combined with ‘matrix-assisted laser desorption ionization- time of flight mass spectrometry’ (MALDI-TOF MS) and PCR methods for detecting the presence of different Yersinia species. Yersinia spp. were recovered from 57.43% of the sampled house sparrows, of which 4.06%, 53.30% and 69.54% were identified as Y. pseudotuberculosis, Y. enterocolitica and other Yersinia species, respectively. Presence of Yersinia was related to the degree of urbanization, average daily temperatures and the community of granivorous birds present at sparrow capture locations. Body condition of suburban house sparrows was found to be higher compared to urban and rural house sparrows, but no relationships between sparrows’ body condition and presence of Yersinia spp. were found. We conclude that two determinants of pathogen infection dynamics, body condition and pathogen occurrence, vary along an urbanization gradient, potentially mediating the impact of urbanization on avian health.

Host Stress Drives Salmonella Recrudescence (vol 6, 20849, 2016)

Scientific Reports 6: Article number: 20849; 10.1038/srep20849 published online: February092016; updated: April152016. In the Supplementary Information file originally published with this Article, Figures S1-4, Tables S1, S2, S4 and S5 were omitted. This error has been corrected in the Supplementary Information that now accompanies the Article.