Search

Equine piroplasmosis (EP) is a tick-borne disease affecting horses, donkeys, mules and zebras, caused by the intracellular apicomplexan protozoa Babesia caballi and Theileria equi . The geographical distribution of EP is closely related to the distribution of its vector tick species belonging to the genera of Dermacentor, Rhipicephalus and Hyalomma . Since the discovery of Dermacentor reticulatus ticks in 2007 and the first reported autochthonous cases in the South of the Netherlands in 2012, no data on the (sero)prevalence of EP in horses in the Netherlands have been reported and it remains unclear whether B. caballi and T. equi have been able to establish themselves in the Netherlands. This study aims to give an update on the current status of EP in horses in the Netherlands using data from serological tests performed in the context of export and screening of 12,881 horses from 2015 through 2020. Horses were categorized as "Dutch," "Foreign," or "Unknown" based on microchip number. The overall seroprevalence of EP in Dutch horses was found to be 0.5% (95% exact CI [0.4-0.7]), compared to 1.9% (95% exact CI [1.3-2.6]) in horses in the category "Foreign" and 1.7% (95% exact CI [1.2-2.3]) in horses in the category "Unknown." In addition, the seroprevalence per country in the category "Foreign" ranged from 0% (0.95% exact CI [0-2.8]) for Ireland to 6.0% (0.95% exact CI [3.5-9.3]) for Spain. In light of the reports on the seroprevalence during the outbreak of autochthonous EP reported in 2012 and on seroprevalences of EP in other countries in Northwestern Europe, the seroprevalence of EP in horses exported from the Netherlands is very low. However, the higher seroprevalence of EP in horses from abroad warrants the need for the monitoring of EP, as tick vectors are present in the Netherlands and the import of horses from endemic areas increases the chances of EP becoming more prevalent in the Netherlands., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Graham, van Kalsbeek, van der Goot and Koene.)

Background: Broilers are among the most common and dense poultry production systems, where antimicrobials have been used extensively to promote animal health and performance. The continuous usage of antimicrobials has contributed to the appearance of resistant bacteria, such as extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec). Here, we studied the ESBL-Ec prevalence and successional dynamics of the caecal microbiota of developing broilers in a commercial flock during their production life cycle (0-35 days). Broilers were categorised as ESBL-Ec colonised (ESBL-Ec + ) or ESBL-Ec non-colonised (ESBL-Ec - ) by selective culturing. Using 16S rRNA gene sequencing, we i. compared the richness, evenness and composition of the caecal microbiota of both broilers' groups and ii. assessed the combined role of age and ESBL-Ec status on the broilers' caecal microbiota., Results: From day two, we observed an increasing linear trend in the proportions of ESBL-Ec throughout the broilers' production life cycle, X 2 (1, N = 12) = 28.4, p < 0.001. Over time, the caecal microbiota richness was consistently higher in ESBL-Ec - broilers, but significant differences between both broilers' groups were found exclusively on day three (Wilcoxon rank-sum test, p = 0.016). Bray-Curtis distance-based RDA (BC-dbRDA) showed no explanatory power of ESBL-Ec status, while age explained 14% of the compositional variation of the caecal microbiota, F (2, 66) = 6.47, p = 0.001., Conclusions: This study assessed the role of ESBL-Ec in the successional dynamics of the caecal microbiota in developing broilers and showed that the presence of ESBL-Ec is associated with mild but consistent reductions in alpha diversity and with transient bacterial compositional differences. We also reported the clonal spread of ESBL-Ec and pointed to the farm environment as a likely source for ESBLs., (© 2022. The Author(s).)

Chlamydia psittaci was considered the predominant chlamydial species in poultry until Chlamydia gallinacea was discovered in 2009. C. psittaci is a zoonotic obligate intracellular bacterium reported in more than 465 bird species including poultry. In poultry, infections can result in asymptomatic disease, but also in more severe systemic illness. The zoonotic potential of C. gallinacea has yet to be proven. Infections in poultry appear to be asymptomatic and in recent prevalence studies C. gallinacea was the main chlamydial species found in chickens. The high prevalence of C. gallinacea resulted in the question if an infection with C. gallinacea might protect against an infection with C. psittaci. To investigate possible cross protection, chickens were inoculated with C. gallinacea NL&#95;G47 and subsequently inoculated with either a different strain of C. gallinacea (NL&#95;F725) or C. psittaci. Chickens that had not been pre-inoculated with C. gallinacea NL&#95;G47 were used as a C. gallinacea or C. psittaci infection control. In the groups that were inoculated with C. psittaci, no difference in pharyngeal or cloacal shedding, or in tissue dissemination was observed between the control group and the pre-inoculated group. In the groups inoculated with C. gallinacea NL&#95;F725, shedding in cloacal swabs and tissues dissemination was lower in the group pre-inoculated with C. gallinacea NL&#95;G47. These results indicate previous exposure to C. gallinacea does not protect against an infection with C. psittaci, but might protect against a new infection of C. gallinacea., (© 2021. The Author(s).)

Chlamydia gallinacea is a recently discovered and widespread obligate intracellular bacterium in chickens. In chickens, infections appear to be asymptomatic, but can result in reduced weight gain in broilers. Molecular typing revealed C. gallinacea is genetically diverse which might lead to differences in pathogenic potential between strains. However, studies about the pathogenesis of different C. gallinacea strains are still limited. In this study, the pathogenesis of C. gallinacea strain NL&#95;G47 was investigated in three consecutive animal experiments. The first experiment served as a pilot in which a maximum culturable dose was administered orally to 13 chickens. Excretion of chlamydial DNA in cloacal swabs was measured during 11 days post infection, but no clinical signs were observed. The second and third experiment were a repetition of the first experiment, but now chickens were sacrificed at consecutive time points to investigate tissue dissemination of C. gallinacea. Again excretion of chlamydial DNA in cloacal swabs was detected and no clinical signs were observed in line with the results of the first experiment. PCR and immunohistochemistry of tissue samples revealed C. gallinacea infected the epithelium of the jejunum, ileum and caecum. Furthermore, C. gallinacea could be detected in macrophages in the lamina propria and in follicular dendritic cells (FDCs) of the B cell follicles in the caecal tonsil. Results of serology showed a systemic antibody response from day seven or eight and onward in all three experiments. The experiments with strain NL&#95;G47 confirmed observations from field studies that C. gallinacea infection does not result in acute clinical disease and mainly resides in the epithelium of the gut. Whether the presence of C. gallinacea results in chronic persistent infections with long term and less obvious health effects in line with observations on other infections caused by Chlamydiae, needs further investigation., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

To combat antimicrobial resistance (AMR), policymakers need an overview of evolution and trends of AMR in relevant animal reservoirs, and livestock is monitored by susceptibility testing of sentinel organisms such as commensal E. coli. Such monitoring data are often vast and complex and generates a need for outcome indicators that summarize AMR for multiple antimicrobial classes. Model-based clustering is a data-driven approach that can help to objectively summarize AMR in animal reservoirs. In this study, a model-based cluster analysis was carried out on a dataset of minimum inhibitory concentrations (MIC), recoded to binary variables, for 10 antimicrobials of commensal E. coli isolates (N = 12,986) derived from four animal species (broilers, pigs, veal calves and dairy cows) in Dutch AMR monitoring, 2007-2018. This analysis revealed four clusters in commensal E. coli in livestock containing 201 unique resistance combinations. The prevalence of these combinations and clusters differs between animal species. Our results indicate that to monitor different animal populations, more than one indicator for multidrug resistance seems necessary. We show how these clusters summarize multidrug resistance and have potential as monitoring outcome indicators to benchmark and prioritize AMR problems in livestock., (© 2021 The Authors. Zoonoses and Public Health published by Wiley-VCH GmbH.)

Extended spectrum beta-lactamase (ESBL)-producing bacteria are resistant to extended-spectrum cephalosporins and are common in broilers. Interventions are needed to reduce the prevalence of ESBL-producing bacteria in the broiler production pyramid. This study investigated two different interventions. The effect of a prolonged supply of competitive exclusion (CE) product and compartmentalization on colonization and transmission, after challenge with a low dose of ESBL-producing Escherichia coli , in broilers kept under semi-field conditions, were examined. One-day-old broilers (Ross 308) ( n = 400) were housed in four experimental rooms, subdivided in one seeder (S/C1)-pen and eight contact (C2)-pens. In two rooms, CE product was supplied from day 0 to 7. At day 5, seeder-broilers were inoculated with E. coli strain carrying bla CTX-M- 1 on plasmid IncI1 (CTX-M-1- E. coli ). Presence of CTX-M-1- E. coli was determined using cloacal swabs (day 5-21 daily) and cecal samples (day 21). Time until colonization and cecal excretion (log 10 CFU/g) were analyzed using survival analysis and linear regression. Transmission coefficients within and between pens were estimated using maximum likelihood. The microbiota composition was assessed by 16S ribosomal RNA gene amplicon sequencing in cecal content of broilers on days 5 and 21. None of the CE broilers was CTX-M-1- E. coli positive. In contrast, in the untreated rooms 187/200 of the broilers were CTX-M-1- E. coli positive at day 21. Broilers in C2-pens were colonized later than seeder-broilers (Time to event Ratio 3.53, 95% CI 3.14 to 3.93). The transmission coefficient between pens was lower than within pens (3.28 × 10 -4 day -2 , 95% CI 2.41 × 10 -4 to 4.32 × 10 -4 vs. 6.12 × 10 -2 day -2 , 95% CI 4.78 × 10 -2 to 7.64 × 10 -2 ). The alpha diversity of the cecal microbiota content was higher in CE broilers than in control broilers at days 5 and 21. The supply of a CE product from day 0 to 7 prevented colonization of CTX-M-1- E. coli after challenge at day 5, likely as a result of CE induced effects on the microbiota composition. Furthermore, compartmentalization reduced transmission rate between broilers. Therefore, a combination of compartmentalization and supply of a CE product may be a useful intervention to reduce transmission and prevent colonization of ESBL/pAmpC-producing bacteria in the broiler production pyramid., (Copyright © 2020 Dame-Korevaar, Kers, van der Goot, Velkers, Ceccarelli, Mevius, Stegeman and Fischer.)

Broilers are an important reservoir of extended spectrum beta-lactamase and AmpC beta-lactamase (ESBL/pAmpC)-producing bacteria. In previous studies, a single supply of a competitive exclusion (CE) product before challenge with a high dose of ESBL/pAmpC-producing Escherichia coli led to reduced colonization, excretion, and transmission, but could not prevent colonization. The hypothesized mechanism is competition; therefore, in this study the effect of a prolonged supply of CE products on colonization, excretion, and transmission of ESBL-producing E. coli after challenge with a low dose at day 0 or day 5 was investigated. Day-old broilers (Ross 308) (n = 220) were housed in isolators. Two CE products, containing unselected fermented intestinal bacteria (CEP) or a selection of pre- and probiotics (SYN), were supplied in drinking water from day 0 to 14. At day 0 or 5, broilers were challenged with 0.5 mL with 10 1 or 10 2  cfu/mL E. coli encoding the beta-lactamase gene bla CTX-M-1 on an IncI plasmid (CTX-M-1-E. coli). Presence and concentration of CTX-M-1-E. coli were determined using cloacal swabs (days 0-14, 16, 19, and 21) and cecal content (day 21). Cox proportional hazard model and a mixed linear regression model were used to determine the effect of the intervention on colonization and excretion (log 10  cfu/g). When challenged on the day of hatch, no effect of CEP was observed. When challenged at day 5, both CEP and SYN led to a prevention of colonization with CTX-M-1-E. coli in some isolators. In the remaining isolators, we observed reduced time until colonization (hazard ratio between 3.71 × 10 -3 and 3.11), excretion (up to -1.60 log 10  cfu/g), and cecal content (up to -2.80 log 10  cfu/g), and a 1.5 to 3-fold reduction in transmission rate. Colonization after a low-dose challenge with ESBL-producing E. coli can be prevented by CE products. However, if at least 1 bird is colonized it spreads through the whole flock. Prolonged supply of CE products, provided shortly after hatch, may be applicable as an intervention to reduce the prevalence of ESBL/pAmpC-producing bacteria in the broiler production chain., (Copyright © 2020. Published by Elsevier Inc.)

The aim of this article is to report on antimicrobial resistance (AMR) in commensal Escherichia coli from livestock from several European countries. The relationships with antimicrobial usage (AMU) at country level and harmonized indicators to cover the most relevant AMR aspects for human health in animal production were also investigated. E. coli were isolated in faeces from broilers and fattening pigs (from nine countries), and fattening turkeys and veal calves (from three countries) and screened against a fixed antimicrobial panel. AMU data were collected at farm and average treatment incidences stratified by antimicrobial class, country and livestock species were calculated. Associations between AMR and AMU at country level were analysed. Independent of animal species, the highest resistance was observed for ampicillin, sulphamethoxazole, tetracycline and trimethoprim. E. coli from broilers showed the highest resistance level for (fluoro)quinolones, and multidrug resistance peaked in broilers and fattening turkeys. Colistin resistance was observed at very low levels with the exception of fattening turkeys. High resistance to third- and fourth-generation cephalosporins was detected in broilers and fattening turkeys. The lowest levels of resistance were for meropenem, azithromycin and tigecycline (<1 %). Significant correlations between resistance and usage at country level were detected in broilers for polymyxins and aminoglycosides, and in fattening pigs for cephalosporins, amphenicols, fluoroquinolones and polymyxins. None of the correlations observed between AMR and AMU were statistically significant for fattening turkey and veal calves. The strength of the analysis performed here is the correlation of aggregated data from the same farms at country level for both AMU and AMR within antimicrobial classes.

Plasmid-mediated extended-spectrum β-lactamase and AmpC β-lactamase (ESBL/pAmpC) producing bacteria are present at all levels of the broiler production pyramid. Young birds can be found positive for ESBL/pAmpC-producing Escherichia coli shortly after arrival at farm. The aim of this study was to determine the effect of different challenge doses of ESBL/pAmpC-producing E. coli on time-until-colonization and the level of excretion in young broilers. One-day-old broilers (specific-pathogen free (SPF) and conventional Ross 308) were housed in isolators and challenged with 0.5 ml ESBL/pAmpC-producing E. coli strains of varying doses (10 1 -10 5  CFU/ml). Presence and concentration (CFU/gram feces) of ESBL/pAmpC-producing E. coli and total E. coli were determined longitudinally from cloacal swabs, and in cecal content 72 h after challenge. Higher challenge doses resulted in shorter time-until-colonization. However, even the lowest dose (10 1  CFU/ml) resulted in colonization of the broilers which excreted >10 6  CFU/gram feces 72 h after inoculation. Conventional broilers were colonized later than SPF broilers, although within 72 h after challenge all broilers were excreting ESBL/pAmpC-producing E. coli. A probabilistic model was used to estimate the probability of colonization by initial inoculation or transmission. The higher the dose the higher the probability of excreting ESBL/pAmpC-producing E. coli as a result of inoculation. In conclusion, low initial doses of ESBL/pAmpC-producing E. coli can result in rapid colonization of a flock. Interventions should thus be aimed to eliminate ESBL/pAmpC-producing bacteria in the environment of the hatchlings and measures focusing at reducing colonization and transmission of ESBL/pAmpC-producing E. coli should be applied shortly after hatching., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The fine-scale temporal dynamics of the chicken gut microbiome are unexplored, but thought to be critical for chicken health and productivity. Here, we monitored the fecal microbiome of healthy chickens on days 1-7, 10, 14, 21, 28, and 35 after hatching, and performed 16S rRNA amplicon sequencing in order to obtain a high-resolution census of the fecal microbiome over time. In the period studied, the fecal microbiomes of the developing chickens showed a linear-log increase in community richness and consistent shifts in community composition. Three successional stages were detected: the first stage was dominated by vertically transmitted or rapidly colonizing taxa including Streptococcus and Escherichia/Shigella; in the second stage beginning on day 4, these taxa were displaced by rapid-growing taxa including Lachnospiraceae and Ruminococcus-like species variants; and in the third stage, starting on day 10, slow-growing, specialist taxa including Candidatus Arthrobacter and Romboutsia were detected. The patterns of displacement and the previously reported ecological characteristics of many of the dominant taxa observed suggest that resource competition plays an important role in regulating successional dynamics in the developing chicken gut. We propose that the boundaries between successional stages (3-4 and 14-21 days after hatching) may be optimal times for microbiome interventions., (© 2019 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

BackgroundMonitoring of antimicrobial resistance (AMR) in animals is essential for public health surveillance. To enhance interpretation of monitoring data, evaluation and optimisation of AMR trend analysis is needed.AimsTo quantify and evaluate trends in AMR in commensal Escherichia coli , using data from the Dutch national AMR monitoring programme in livestock (1998-2016).MethodsFaecal samples were collected at slaughter from broilers, pigs and veal calves. Minimum inhibitory concentration values were obtained by broth microdilution for E. coli for 15 antimicrobials of eight antimicrobial classes. A Poisson regression model was applied to resistant isolate counts, with explanatory variables representing time before and after 2009 (reference year); for veal calves, sampling changed from 2012 represented by an extra explanatory variable.ResultsResistant counts increased significantly from 1998-2009 in broilers and pigs, except for tetracyclines and sulfamethoxazole in broilers and chloramphenicol and aminoglycosides in pigs. Since 2009, resistant counts decreased for all antimicrobials in broilers and for all but the phenicols in pigs. In veal calves, for most antimicrobials no significant decrease in resistant counts could be determined for 2009-16, except for sulfamethoxazole and nalidixic acid. Within animal species, antimicrobial-specific trends were similar.ConclusionsUsing Dutch monitoring data from 1998-2016, this study quantified AMR trends in broilers and slaughter pigs and showed significant trend changes in the reference year 2009. We showed that monitoring in commensal E. coli is useful to quantify trends and detect trend changes in AMR. This model is applicable to similar data from other European countries.

Plasmid mediated Extended Spectrum Beta-Lactamase and AmpC Beta-Lactamase (ESBL/pAmpC) producing bacteria are resistant to beta-lactam antimicrobials and are widespread in humans, the environment and animals. Animals, especially broilers, are an important reservoir of ESBL/pAmpC producing bacteria. To control ESBL/pAmpC prevalence in broilers, transmission within the entire broiler production pyramid should be considered. This study, including 103 articles originating from two electronic databases, searched for evidence for possible routes of transmission of ESBL/pAmpC producing bacteria in the broiler production pyramid. Possible routes of transmission were categorised as 1) vertical between generations, 2) at hatcheries, 3) horizontal on farm, and 4) horizontal between farms and via the environment of farms. This review presents indications for transmission of ESBL/pAmpC producing bacteria for each of these routes. However, the lack of quantitative results in the literature did not allow an estimation of the relative contribution or magnitude of the different routes. Future research should be specifically targeted towards such information as it is crucial to guide reduction strategies for the spread of ESBL/pAmpC producing bacteria in the broiler production chain., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Extended-spectrum beta-lactamase producing E. coli (ESBL-E) are wide spread among broilers, with the highest prevalence among individual birds at broiler production farms. Previous research describes low prevalences among individual birds at arrival at the farm (below 30%), and a rapid increase up to 100% within the first week. Our goal was to investigate whether this rapid increase was due to latent contamination of ESBL-E or to contamination at the broiler farm. Two broiler groups, one hatched at a conventional hatchery and the other individually hatched in an ESBL-free environment, were housed individually in an experimental ESBL-free environment. A third group was hatched at a conventional hatchery and kept at a conventional broiler farm. The birds were sampled daily during the first week after hatch and tested for the presence of ESBL-E. In addition ESBL-E presence in eggs that were not incubated was investigated. All birds and eggs came from one ESBL-E positive parent flock. ESBL/AmpC genes, plasmids and E. coli sequence types were determined for a selection of isolates. ESBL-E was never found in the two groups kept in the ESBL-free experimental environment or in the sampled eggs, whereas all broilers sampled at the conventional farm became positive for ESBL-E within three days. One dominant E. coli strain (ST88) carrying bla CTX-M-1 gene on an IncI1/pST3 plasmid was found in parent and broiler samples. We conclude that the rapid increase in ESBL-E prevalence in the first week of life is not caused by a latent contamination of the majority of birds at arrival, but that this increase must be caused by other factors., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The bla SHV-12 β-lactamase gene is one of the most prevalent genes conferring resistance to extended-spectrum β-lactams in Enterobacteriaceae disseminating within and between reservoirs, mostly via plasmid-mediated horizontal gene transfer. Yet, studies regarding the biology of plasmids encoding bla SHV-12 are very limited. In this study, we revealed the emergence of IncX3 plasmids alongside IncI1α/γ in bla SHV-12 in animal-related Escherichia coli isolates. Four representative bla SHV-12 -encoding IncX3 plasmids were selected for genome sequencing and further genetic and functional characterization. We report here the first complete sequences of IncX3 plasmids of animal origin and show that IncX3 plasmids exhibit remarkable synteny in their backbone, while the major differences lie in their bla SHV-12 -flanking region. Our findings indicate that plasmids of this subgroup are conjugative and highly stable, while they exert no fitness cost on their bacterial host. These favourable features might have contributed to the emergence of IncX3 amongst SHV-12-producing E. coli in the Netherlands, highlighting the epidemic potential of these plasmids.

Extended-spectrum β-lactamase and plasmid mediated AmpC β-lactamase (ESBL/pAmpC) producing bacteria are resistant to Extended Spectrum Cephalosporins (ESC), and are present in all levels of the broiler production chain. We determined the prevalence, concentration, and persistence of ESBL/pAmpC-Escherichia coli in a broiler parent flock during the rearing and laying period. One-day old chickens were housed in four separate pens. Until week 33 no antibiotics or coccidiostatics were used. During rearing 57 chickens in each pen (n=228), and in the laying period two groups of 33 chickens were individually sampled (n=66). Environmental samples were taken from week 16 onwards. ESBL/pAmpC-E. coli presence was determined by selective culturing. In the samples of week 16-19 the concentration of ESBL/pAmpC-E. coli was determined. All ESC-resistant isolates found were positive for pAmpC gene bla CMY-2 located on IncA/C plasmids, in several E. coli MLST types. CMY-2-E. coli prevalence decreased from 91% (95%CI 86-94%) at day 7 (week 1) to 0% (95%CI 0-5%) in week 21. However, CMY-2-E. coli remained present in the environmental samples during the whole study. CMY-2-E. coli concentration varied between detection limit (<10^3) and 2·10^4 cfu/g faeces. The sharp reduction of CMY-2-E. coli in this broiler parent flock in absence of antibiotics suggests a selective disadvantage of bla CMY-2 on IncA/C plasmids on animal level. The underlying mechanism should be studied further as this may provide new insights on how to reduce ESBL/pAmpC prevalence and transmission in the broiler production chain., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objectives: The aim of this study was to establish the prevalence of extended-spectrum β-lactamase (ESBL)- and AmpC β-lactamase-producing Escherichia coli at Dutch broiler farms and in farmers and to compare ESBL/AmpC-producing isolates from farmers and their animals., Methods: Twenty-five to 41 cloacal swabs collected from broilers at each of 26 farms and 18 faecal samples from 18 broiler farmers were analysed for determination of the presence of ESBL/AmpC-producing E. coli. ESBL/AmpC genes were characterized by microarray, PCR and sequencing. Plasmids were characterized by transformation and PCR-based replicon typing. Subtyping of plasmids was done by plasmid multilocus sequence typing or restriction fragment length polymorphism. E. coli genotypes were determined by multilocus sequence typing., Results: Birds from all farms were positive for ESBL/AmpC-producing E. coli, and on 22/26 farms the within-farm prevalence was ≥ 80%. Six of 18 farmers carried isolates containing ESBL/AmpC genes bla(CTX-M-1), bla(CMY-2) and/or bla(SHV-12), which were also present in the samples from their animals. In five of these isolates, the genes were located on identical plasmid families [IncI1 (n = 3), IncK (n = 1) or IncN (n = 1)], and in isolates from two farmers the genes were carried on identical plasmid subtypes (IncI1 ST12 and IncN ST1, where ST stands for sequence type) as in the isolates from their animals., Conclusions: This study shows a high prevalence of birds carrying ESBL/AmpC-producing E. coli at Dutch broiler farms and a high prevalence of ESBL/AmpC-producing E. coli in farmers. This is undesirable due to the risk this poses to human health. Future research should focus on identification of the source of these isolates in the broiler production chain to make interventions resulting in reduction of these isolates possible.

Even though low pathogenic avian influenza viruses (LPAIv) affect the poultry industry of several countries in the world, information about their transmission characteristics in poultry is sparse. Outbreak reports of LPAIv in layer chickens have described drops in egg production that appear to be correlated with the virus transmission dynamics. The objective of this study was to use egg production data from LPAIv infected layer flocks to quantify the within-flock transmission parameters of the virus. Egg production data from two commercial layer chicken flocks which were infected with an H7N3 LPAIv were used for this study. In addition, an isolate of the H7N3 LPAIv causing these outbreaks was used in a transmission experiment. The field and experimental estimates showed that this is a virus with high transmission characteristics. Furthermore, with the field method, the day of introduction of the virus into the flock was estimated. The method here presented uses compartmental models that assume homogeneous mixing. This method is, therefore, best suited to study transmission in commercial flocks with a litter (floor-reared) housing system. It would also perform better, when used to study transmission retrospectively, after the outbreak has finished and there is egg production data from recovered chickens. This method cannot be used when a flock was affected with a LPAIv with low transmission characteristics (R(0)<2), since the drop in egg production would be low and likely to be confounded with the expected decrease in production due to aging of the flock. Because only two flocks were used for this analysis, this study is a preliminary basis for a proof of principle that transmission parameters of LPAIv infections in layer chicken flocks could be quantified using the egg production data from affected flocks., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The transmissibility of an H7N1 Low Pathogenic Avian Influenza (LPAI) virus isolated from a turkey flock during the large epidemic in Italy in 1999, was experimentally studied in chickens. Four group transmission experiments were performed. Infection and transmission were monitored by means of virus isolation on swab samples and antibody detection in serum samples. From the results of these groups, we estimated the mean infectious period at 7.7 (6.7-8.7) days, the transmission rate parameter at 0.49 (0.30-0.75) infections per infectious chicken per day and the basic reproduction ratio at 3.8 (1.3-6.3). These estimates can be used for the development of surveillance and control programmes of LPAI in poultry., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The poultry epidemic of H7N7 highly pathogenic avian influenza (HPAI) virus in the Netherlands in 2003 was probably the result of the introduction of an H7N7 low pathogenic avian influenza (LPAI) virus (by interspecies transmission from wild birds) and the subsequent intraspecies transmission of this virus in poultry. The intraspecies transmission of the ensuing H7N7 HPAI virus was very successful both within and between flocks. Consequently, in the two poultry-dense areas that were affected, the epidemic could only be stopped by eliminating all poultry in the region. According to the spatial models these are the only areas where this was the case in the Netherlands. There was also interspecies transmission to mammals, i.e., to pigs and to humans. For pigs it was shown that possible subsequent intraspecies transmission was negligible (R0 <1). With hindsight the same was probably also true for humans.

Twenty-four haemolytic Escherichia coli strains were isolated from dogs with diarrhea. The strains were serotyped and analysed by polymerase chain reaction (PCR) for genes encoding virulence factors associated with E. coli that cause diarrhea in animals. Adhesion antigen production was deduced from haemagglutination experiments. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of heat extracts was also used as an indication for the production of adhesive structures. The majority of the strains was shown to produce this type of virulence factor. Adhesion and invasion tests of the strains and Caco-2 cells showed that all strains adhered and that two were invasive. The two invasive strains were positive in the intimin PCR and one of them also contained genes encoding CS31A. The PCR for heat stable toxin (ST) was positive in only four strains, as was the presence of F17 fimbrial genes. Surprisingly, 19 strains had intact P fimbrial operons, coding for an adhesin involved in urinary tract infection (UTI). The cytotoxic necrotising factor 1 (CNF1) gene, also mainly found in UTI was likewise detected in these 19 strains. Cytolethal distending toxin (Cdt) genes were found in five strains. The high number of strains positive for CNF1 and P fimbriae prompted us to test the strains in a multiplex PCR used to test E. coli isolated from UTI in various species for 30 virulence associated genes. The data showed that the majority of the diarrhea isolates have virulence factor profiles highly similar to UTI E. coli isolates from dogs. This raises the question whether these isolates are real intestinal pathogens or "innocent bystanders". However, since CNF1 producing necrotoxic E. coli (NTEC) strains isolated from humans, pigs and calves with diarrhea appear to be highly related to our strains, it might be that in dogs this type of isolate is capable of causing not only UTI, but also diarrhea. If this is the case and this type of isolate is "bifunctional", domestic animals likely constitute a reservoir of NTEC strains which can be also pathogenic for humans.