Prevalence of enteropathogenic Escherichia coli in naturally occurring cases of poult enteritis-mortality syndrome

Enteric Viruses Associated with Mid-growth Turkey Enteritis

Since August 2014, the University of Minnesota Veterinary Diagnostic Laboratory has received cases of turkey enteritis that are clinically different from previously described cases of poult enteritis syndrome and light turkey syndrome. The birds develop dark green and extremely foul-smelling diarrhea starting at 8-10 wk of age, which may last up to 15-16 wk of age. The affected turkey flocks show poor uniformity, and feed conversion and market weights are reduced. Multiple-age farms are affected more often than the single-age farms. Morbidity varies from flock to flock and in some cases reaches 100%. At necropsy, undigested feed with increased mucus is observed in the intestines along with prominent mucosal congestion and/or hemorrhage. Microscopically, lymphocytic infiltrates expand the villi in duodenum and jejunum to form lymphoid follicles, which are often accompanied by heterophils. Next generation sequencing (Illumina Miseq) on a pool of feces from affected birds identified genetic sequences of viruses belonging to Astroviridae, Reoviridae, Picornaviridae, Picobirnaviridae, and Adenoviridae. On testing pools of fecal samples from apparently healthy (16 pools) and affected birds (30 pools), there was a higher viral load in the feces of affected birds. Picobirnavirus was detected only in the affected birds; 20 of 30 pools (66.7%) were positive. These results indicate that a high viral load of turkey picobirnavirus alone, or in association with novel picornaviruses, may be a cause of this new type of turkey enteritis.

First isolation of atypical enteropathogenic Escherichia coli from geese (Anser anser domestica) and first description of atypical EPEC from turkeys and pigeons in Hungary

Background

Escherichia coli is a bacterial species widely distributed among mammals and avian species, and also a member of the normal intestinal microbiota. However, some E. coli strains of different pathotypes can cause disease in both humans and animals. Atypical enteropathogenic E. coli (aEPEC) can infect both animals and humans or influence the severity of other ongoing infections.

Results

In the present study, a total of 332 samples were collected from ducks, geese, turkeys, chickens, and pigeons from the Hungarian Veterinary Diagnostic Directorate, two slaughterhouses, two pigeon keepers and one backyard chicken farm. E. coli was isolated and verified from 319 samples. The isolates were screened by PCR for diarrheagenic E. coli pathotypes. Altogether seven atypical enteropathogenic E. coli (aEPEC) strains were identified: two from four-week-old dead turkeys, two from force-fed geese, and three from pigeons. No further pathotypes were identified in the collection. The atypical EPEC strains were classified phylogenetically to B1, B2, and F, and four out of the seven aEPEC isolates proved to be multidrug resistant. Serotypes of aEPEC strains were uniform collected from same farms and showed diversity between their origins with O76, O145, O109 serogroups.

Conclusions

This is the first report in the literature about aEPEC in goose (Anser anser domestica). Furthermore, this is the first isolation of aEPEC from turkeys and pigeons in Hungary. The uneven distribution of aEPEC in different age groups of poultry suggests that aEPEC disappears with growing up, but stress (e.g.: force-feeding) and concurrent diseases might promote its reappearance in the intestine.

Poult Enteritis and Mortality Syndrome in Turkey Poults: Causes, Diagnosis and Preventive Measures

Simple Summary

The poult enteritis and mortality syndrome (PEMS) causes severe economic losses in turkeys. Several agents were described to be associated with the PEMS; however, a specific etiological agent(s) has not been identified. The diagnosis of PEMS is still a huge challenge for several reasons: (1) no specific clinical signs or pathognomonic lesions, (2) isolation of some enteric viruses still difficult, (3) the pathogenicity of several enteric viruses in turkeys is not fully understood, (4) PEMS is an interaction between several known and might be unknown agents and (5) opportunistic microorganisms also have a role in the pathogenesis of PEMS. Both electron microscopy and molecular techniques can be used for diagnosis of PEMS and might help to discover unknown causes. Until now, no specific vaccines against enteric viruses associated with PEMS. However, biosecurity, maintaining a healthy gut and strengthening the immune system of turkey poults using probiotics, prebiotics and/or phytogenic substances are crucial factors to prevent and/or reduce losses of PEMS in turkeys. This review is a call for scientists to perform further research to investigate the real cause(s) of PEMS and to develop a preventive strategy against it.

Abstract

Poult enteritis and mortality syndrome (PEMS) is one of the most significant problem affecting turkeys and continues to cause severe economic losses worldwide. Although the specific causes of PEMS remains unknown, this syndrome might involve an interaction between several causative agents such as enteropathogenic viruses (coronaviruses, rotavirus, astroviruses and adenoviruses) and bacteria and protozoa. Non-infectious causes such as feed and management are also interconnected factors. However, it is difficult to determine the specific cause of enteric disorders under field conditions. Additionally, similarities of clinical signs and lesions hamper the accurate diagnosis. The purpose of the present review is to discuss in detail the main viral possible causative agents of PEMS and challenges in diagnosis and control.

High Frequency of Multidrug-Resistant (MDR) Atypical Enteropathogenic Escherichia coli (aEPEC) in Broilers in Hungary

Escherichia coli (EC) strains belong to several pathotypes capable of infecting both humans and animals. Some of them have zoonotic potential and can sporadically cause epidemic outbreaks. Our aim was to screen for the distribution of these pathotypes in broilers and their related products. Therefore, E. coli strains were isolated (n = 118) from poultry intestine (n = 57), carcass (n = 57), and wastewater (n = 4) samples from one slaughterhouse with own reared poultry source and the National Reference Laboratory (NRL) poultry E. coli collection (n = 170) from the year 2017 was also studied. All 288 E. coli strains were screened by PCR for pathotype-specific genes stx, eae, st-lt, aggR, ipaH, and for further EPEC-specific virulence genes (bfp, EAF, tir, perA, ler). Altogether 35 atypical enteropathogenic E. coli (aEPEC) strains from the slaughterhouse and 48 aEPEC strains from the NRL collection were found. Regarding the phylogenetic groups of aEPEC, all four main groups were represented but there was a shift toward the B2 group (25%) as compared with the non-EPEC isolates (3%). The aEPEC isolates belonged to serogroups O14, O108, and O45. Multidrug resistance (MDR) was abundant in aEPEC strains (80 out of 83 aEPEC) with a diverse resistance pattern (n = 56). Our results of this study indicate that the high frequency of aEPEC in broilers and on their carcass surface, with frequent MDR to several antibiotic groups, raises the possibility that these strains pose a zoonotic risk to humans.

Novel Hybrid of Typical Enteropathogenic Escherichia coli and Shiga-Toxin-Producing E. coli (tEPEC/STEC) Emerging From Pet Birds

Exotic psittacine birds have been implicated as reservoir of diarrheagenic Escherichia coli (E. coli), including enteropathogenic E. coli (EPEC) and Shiga-toxin producing E. coli (STEC). Here, we present a genotypic and phenotypic characterization of typical EPEC/STEC hybrid strains isolated from exotic psittacine birds. The strains were positive for eae, bfpA, and stx2f genes, belong to serotype O137:H6 and ST2678. Two strains were subject to whole genome sequencing, confirming the presence of the virulence factors of both E. coli pathotypes. Phenotypical in vitro tests confirmed their ability to adhere to HeLa cells and cause cytotoxicity to Vero cells. The rabbit ileal loop assays showed the attaching and effacing lesion, in addition to inflammatory process and overproduction of intestinal mucus. This is the first report of hybrid typical EPEC/STEC (O137:H6/ST2678) strains isolated from companion psittacine birds and the results suggest zoonotic risks.

Enteric viruses in turkey enteritis

Gut health is very important to get maximum returns in terms of weight gain and egg production. Enteric diseases such as poult enteritis complex (PEC) in turkeys do not allow their production potential to be achieved to its maximum. A number of viruses, bacteria, and protozoa have been implicated but the primary etiology has not been definitively established. Previously, electron microscopy was used to detect the presence of enteric viruses, which were identified solely on the basis of their morphology. With the advent of rapid molecular diagnostic methods and next generation nucleic acid sequencing, researchers have made long strides in identification and characterization of viruses associated with PEC. The molecular techniques have also helped us in identification of pathogens which were previously not known. Regional and national surveys have revealed the presence of several different enteric viruses in PEC including rotavirus, astrovirus, reovirus and coronavirus either alone or in combination. There may still be unknown pathogens that may directly or indirectly play a role in enteritis in turkeys. This review will focus on the role of turkey coronavirus, rotavirus, reovirus, and astrovirus in turkey enteritis.

Molecular detection of enteropathogenic Escherichia coli in asymptomatic captive psittacines

Psittaciformes are one of the most endangered groups of birds, and several Brazilian species are classified between vulnerable and critically endangered. It is thus necessary to identify agents that cause infections in captive wild animals and to assess the risks posed thereof and to design interventions to minimize the possibility of disease outbreaks, leading to the conservation of endangered species. The purpose of this study was to identify enteropathogenic Escherichia coli (EPEC) cloacal isolates from asymptomatic psittacines in captivity and evaluate the distribution of the EPEC pathotype. Cloacal swabs were obtained from 46 asymptomatic birds, and resulting isolates were tested by polymerase chain reaction (PCR) for the presence of the attaching and effacing gene (eae) and bundle-forming pilus structural gene (bfpA) of EPEC. Samples from several species were tested, and three samples were found to be positive for the eae and bfpA genes and characterized as typical EPEC. This is the first report of this pathotype in asymptomatic psittacines. Although certain E. coli strains are more pathogenic than others, various factors should be considered when determining the potential of E. coli isolates to cause disease in captive psittacines. Birds that are positive for the EPEC (typical) strain could be zoonotic sources of infection, and may have acquired these strains through contact with humans or domestic animals. These findings may also be valuable for the long-term management of endangered species ex situ as one EPEC sample was isolated from a Red-tailed Amazon (Amazona brasiliensis).

A Survey for Escherichia coli Virulence Factors in Asymptomatic Free-Ranging Parrots

Parrots in captivity are frequently affected by Escherichia coli (E. coli) infections. The objective of this study was to collect information on the carrier state for E. coli pathotypes in asymptomatic free-ranging parrots. Cloacal swabs were collected from nestlings of Hyacinth, Lear's macaws and Blue-fronted Amazon parrots and tested by polymerase chain reaction (PCR) for virulence factors commonly found in enteropathogenic, avian pathogenic, and uropathogenic E. coli strains. In total, 44 samples were cultured and E. coli isolates were yielded, from which DNA was extracted and processed by PCR. Genes commonly found in APEC isolates from Blue-fronted Amazon parrots and Hyacinth macaws were expressed in 14 of these 44 samples. One atypical EPEC isolate was obtained from a sample from Lear's macaw. The most commonly found gene was the increased serum survival (iss) gene. This is the first report, that describes such pathotypes in asymptomatic free-living parrots. The findings of this study suggest the presence of a stable host/parasite relationship at the time of the sampling brings a new understanding to the role that E. coli plays in captive and wild parrots. Such information can be used to improve husbandry protocols as well as help conservation efforts of free-living populations.

High prevalence of turkey parvovirus in turkey flocks from Hungary experiencing enteric disease syndromes

Samples collected in 2008 and 2009, from 49 turkey flocks of 6 to 43 days in age and presenting clinical signs of enteric disease and high mortality, were tested by polymerase chain reaction and reverse transcription-polymerase chain reaction for the presence of viruses currently associated with enteric disease (ED) syndromes: astrovirus, reovirus, rotavirus, coronavirus, adenovirus, and parvovirus. Turkey astroviruses were found in 83.67% of the cases and turkey astrovirus 2 (TAst-2) in 26.53%. The investigations directly demonstrated the high prevalence of turkey parvovirus (TuPV) in 23 flocks (46.9%) experiencing signs of ED, making this pathogen the second most identified after astroviruses. Phylogenetic analysis on a 527 base pair-long region from the NS1 gene revealed two main clusters, a chicken parvovirus (ChPV) and a TuPV group, but also the presence of a divergent branch of tentatively named "TuPV-like ChPV" strains. The 23 Hungarian TuPV strains were separately positioned in two groups from the American origin sequences in the TuPV cluster. An Avail-based restriction fragment length polymorphism assay has also been developed for the quick differentiation of TuPV, ChPV, and divergent TuPV-like ChPV strains. As most detected enteric viruses have been directly demonstrated in healthy turkey flocks as well, the epidemiology of this disease complex remains unclear, suggesting that a certain combination of pathogens, environmental factors, or both are necessary for the development of clinical signs.

Serogroups and virulence genes of Escherichia coli isolated from psittacine birds

Escherichia coli isolates from 24 sick psittacine birds were serogrouped and investigated for the presence of genes encoding the following virulence factors: attaching and effacing (eae), enteropathogenic E. coli EAF plasmid (EAF), pili associated with pyelonephritis (pap), S fimbriae (sfa), afimbrial adhesin (afa), capsule K1 (neu), curli (crl, csgA), temperature-sensitive hemagglutinin (tsh), enteroaggregative heat-stable enterotoxin-1 (astA), heat-stable enterotoxin -1 heat labile (LT) and heat stable (STa and STb) enterotoxins, Shiga-like toxins (stx1 and stx2), cytotoxic necrotizing factor 1 (cnf1), haemolysin (hly), aerobactin production (iuc) and serum resistance (iss). The results showed that the isolates belonged to 12 serogroups: O7; O15; O21; O23; O54; O64; O76; O84; O88; O128; O152 and O166. The virulence genes found were: crl in all isolates, pap in 10 isolates, iss in seven isolates, csgA in five isolates, iuc and tsh in three isolates and eae in two isolates. The combination of virulence genes revealed 11 different genotypic patterns. All strains were negative for genes encoding for EAF, EAEC, K1, sfa, afa, hly, cnf, LT, STa, STb, stx1 and stx2. Our findings showed that some E. coli isolated from psittacine birds present the same virulence factors as avian pathogenic E. coli (APEC), uropathogenic E. coli (UPEC) and Enteropathogenic E. coli (EPEC) pathotypes.

Detection and molecular characterization of enteric viruses in breeder turkeys

The present study was undertaken to detect and characterize enteric viruses (rotavirus, astrovirus, reovirus, and coronavirus) in breeder poults. Five turkey breeder flocks were selected. Faecal samples were collected from all flocks at 1 week of age and then every other week until the poults reached 9 weeks of age. The faecal samples were pooled in groups of five. Of the 193 pools ("samples") tested by reverse transcription-polymerase chain reaction, 47.2%, 30.6%, and 10.4% samples were positive for astrovirus, rotavirus, and reovirus, respectively. No coronavirus was detected in any of the samples. Overall, 118 (61.1%) samples were positive for one or more enteric viruses. Of the 118 samples, 70 (59.3%) were positive for a single virus and 48 (40.7%) for a combination of viruses. Phylogenetic analysis based on the polymerase gene showed that astroviruses clustered into two groups with sequence homology ranging from 85.6 to 100% at the nucleotide level. Based on NSP4 gene sequences, rotaviruses clustered in a group and had 96.3 to 99.9% sequence homology at the nucleotide level. The reoviruses, based on their S4 gene sequences, clustered in a single group with sequence homology of 96.9 to 100%. Differing amino acid sequences of all three viruses may affect the antigenicity and/or pathogenicity of these viruses and may merit further study. The presence of two or three different viruses in combination may affect the dynamics of turkey health and disease.

Experimental reproduction of poult enteritis syndrome: clinical findings, growth response, and microbiology

Poult enteritis syndrome (PES) is an infectious disease of turkey poults characterized by diarrhea, dullness, and depression. Five experiments were conducted to reproduce the disease in turkey poults using intestinal contents of PES-affected birds. In all experiments, poults at 14 d of age were divided into 4 groups and were orally given 2 mL of unfiltered supernatant, filtered supernatant, sediment dissolved in PBS, or PBS alone. Inocula in experiments 1, 3, and 5 consisted of intestinal contents from PES-affected birds of less than 2 wk of age, whereas those in experiments 2 and 4 consisted of intestinal contents from PES-affected birds of 4 to 6 wk of age. Poults in all groups were observed daily for clinical signs. The BW and microbiological criteria in experiments 1, 3, and 5 were evaluated at 5, 10, and 15 d postinoculation, whereas in experiments 2 and 4, these observations were made at 10 and 20 d postinoculation. Rotavirus, astrovirus, and Salmonella were present in all 5 inocula. Diarrhea and depression were the major signs in poults given PES material. Significant retardation of growth was observed in poults given any of the 3 PES materials, but this effect was more pronounced in poults given the sediment inoculum. Rotavirus, astrovirus, and Salmonella were detected in poults given PES material. In some cases, enterovirus was also detected. No major difference was noticed in experimental reproduction of PES when intestinal contents from different age birds were used as the inoculum.

Attaching-effacing bacteria in animals

Enteric bacteria with a demonstrable or potential ability to form attaching-effacing lesions, so-called attaching-effacing (AE) bacteria, have been found in the intestinal tracts of a wide variety of warm-blooded animal species, including man. In some host species, for example cattle, pigs, rabbits and human beings, attaching-effacing Escherichia coli (AEEC) have an established role as enteropathogens. In other host species, AE bacteria are of less certain significance. With continuing advances in the detection and typing of AE strains, the importance of these bacteria for many hosts is likely to become clearer. The pathogenic effects of AE bacteria result from adhesion to the intestinal mucosa by a variety of mechanisms, culminating in the formation of the characteristic intimate adhesion of the AE lesion. The ability to induce AE lesions is mediated by the co-ordinated expression of some 40 bacterial genes organized within a so-called pathogenicity island, known as the "Locus for Enterocyte Effacement". It is also believed that the production of bacterial toxins, principally Vero toxins, is a significant virulence factor for some AEEC strains. Recent areas of research into AE bacteria include: the use of Citrobacter rodentium to model human AEEC disease; quorum-sensing mechanisms used by AEEC to modulate virulence gene expression; and the potential role of adhesion in the persistent colonization of the intestine by AE bacteria. This review of AE bacteria covers their molecular biology, their occurrence in various animal species, and the diagnosis, pathology and clinical aspects of animal diseases with which they are associated. Reference is made to human pathogens where appropriate. The focus is mainly on natural colonization and disease, but complementary experimental data are also included.

Interaction with avian cells and colonisation of specific pathogen free chicks by Shiga-toxin negative Escherichia coli O157:H7 (NCTC 12900)

The prevalence of Escherichia coli O157:H7 infection in birds is low but several deliberate inoculation studies show that poultry are readily and persistently infected by this organism indicating a possible threat to public health. The mechanisms of colonisation of poultry are not understood and the aim is to establish models to study the interaction of E. coli O157:H7, at the cellular and whole animal levels. A non-toxigenic E. coli O157:H7 (NCTC 12900) was used in adherence assays with an avian epithelial cell line (Div-1) and used to inoculate 1-day-old SPF chicks. In vitro, NCTC 12900 induced micro-colonies associated with cytoskeletal arrangements and pedestal formation with intimate bacterial attachment. In the 1-day-old SPF chick, a dose of 1 x 10(5) cfu resulted in rapid and extensive colonisation of the gastrointestinal tract and transient colonisation of the liver and spleen. The number of E. coli O157:H7 organisms attained approximately 10(8) cfu/ml caecal homogenate 24h after inoculation and approximately 10(7) cfu/ml caecal homogenate was still present at day 92. Faecal shedding persisted for 169 days, ceasing 9 days after the birds came into lay and 6% of eggs were contaminated on the eggshell. Histological analysis of tissue samples from birds dosed with 1x10(7) cfu gave evidence for E. coli O157:H7 NCTC 12900 induced micro-colonies on the caecal mucosa, although evidence for attaching effacing lesions was equivocal. These models may be suitable to study those factors of E. coli O157:H7 that mediate persistent colonisation in avian species.

Enhancement of enteropathogenic Escherichia coli pathogenicity in young turkeys by concurrent turkey coronavirus infection

In a previous study, turkey coronavirus (TCV) and enteropathogenic Escherichia coli (EPEC) were shown to synergistically interact in young turkeys coinfected with these agents. In that study, inapparent or mild disease was observed in turkeys inoculated with only TCV or EPEC, whereas severe growth depression and high mortality were observed in dually inoculated turkeys. The purpose of the present study was to further evaluate the pathogenesis of combined TCV/EPEC infection in young turkeys and determine the role of these agents in the observed synergistic interaction. Experiments were conducted to determine 1) effect of EPEC dose, with and without concurrent TCV infection, and 2) effect of TCV exposure, before and after EPEC exposure, on development of clinical disease. Additionally, the effect of combined infection on TCV and EPEC shedding was determined. No clinical sign of disease and no attaching and effacing (AE) lesions characteristic of EPEC were observed in turkeys inoculated with only EPEC isolate R98/5, even when turkeys were inoculated with 10(10) colony forming units (CFU) EPEC (high dose exposure). Only mild growth depression was observed in turkeys inoculated with only TCV; however, turkeys inoculated with both TCV and 10(4) CFU EPEC (low dose exposure) developed severe disease characterized by high mortality, marked growth depression, and AE lesions. Inoculation of turkeys with TCV 7 days prior to EPEC inoculation produced more severe disease (numerically greater mortality, significantly lower survival probability [P < 0.05], increased frequency of AE lesions) than that observed in turkeys inoculated with EPEC prior to TCV or simultaneously inoculated with these agents. Coinfection of turkeys with TCV and EPEC resulted in significantly increased (P < 0.05) shedding of EPEC, but not TCV, in intestinal contents of turkeys. These findings indicate that TCV infection predisposes young turkeys to secondary EPEC infection and potentiates the expression of EPEC pathogenicity in young turkeys.