Commercial Layer Flocks Research Articles

Revealing the structure of the associations between housing system, facilities, management and welfare of commercial laying hens using Additive Bayesian Networks

After the ban of battery cages in 1988, a welfare control programme for laying hens was developed in Sweden. Its goal was to monitor and ensure that animal welfare was not negatively affected by the new housing systems. The present observational study provides an overview of the current welfare status of commercial layer flocks in Sweden and explores the complexity of welfare aspects by investigating and interpreting the inter-relationships between housing system, production type (i.e. organic or conventional), facilities, management and animal welfare indicators. For this purpose, a machine learning procedure referred to as structure discovery was applied to data collected through the welfare programme during 2010–2014 in 397 flocks housed in 193 different farms. Seventeen variables were fitted to an Additive Bayesian Network model. The optimal model was identified by an exhaustive search of the data iterated across incremental parent limits, accounting for prior knowledge about causality, potential over-dispersion and clustering. The resulting Directed Acyclic Graph shows the inter-relationships among the variables. The animal-based welfare indicators included in this study – flock mortality, feather condition and mite infestation – were indirectly associated with each other. Of these, severe mite infestations were rare (4% of inspected flocks) and mortality was below the acceptable threshold (< 0.6%). Feather condition scored unsatisfactory in 21% of the inspected flocks; however, it seemed to be only associated to the age of the flock, ruling out any direct connection with managerial and housing variables. The environment-based welfare indicators – lighting and air quality – were an issue in 5 and 8% of the flocks, respectively, and showed a complex inter-relationship with several managerial and housing variables leaving room for several options for intervention. Additive Bayesian Network modelling outlined graphically the underlying process that generated the observed data. In contrast to ordinary regression, it aimed at accounting for conditional independency among variables, facilitating causal interpretation.

Analysis of antibody levels in egg yolk for detection of exposure to Ascaridia galli parasites in commercial laying hens

Ascaridia galli is one of the most abundant nematode parasites in poultry. A. galli infections can significantly impact the profitability of egg farms and have negative implications for bird health and welfare. The main objectives of this study were to determine whether A. galli specific antibodies in egg yolks can be used to detect prior or current exposure to A. galli in laying hens, and to distinguish between eggs obtained from caged and free-range hens. Twenty-two laying hen flocks from different production systems (10 free-range, 2 barn-housed, and 9 caged flocks) were enrolled in the study. An in-house enzyme-linked immunosorbent assay was used to analyze levels of A. galli specific antibodies in yolk. The numbers of A. galli eggs in hen excreta were also determined in a subset of farms. Free-range flocks had higher and also more variable levels of anti-A. galli antibodies in the egg yolk compared to those of the cage flocks (0.50 ± 0.39 vs. 0.16 ± 0.13 OD units) (P < 0.001). Results also confirmed that excreta from free-range and barn-housed flocks contained higher numbers of A. galli eggs than did excreta from caged flocks in which no A. galli eggs were detected. In conclusion, analysis of anti-A. galli antibodies in the egg yolk can be used to detect worm exposure in commercial layer flocks. However, the method used in this study cannot be used in isolation to distinguish between eggs from cage and free-range production systems as anti-A galli antibodies were detected in egg yolk samples from all production systems, and the range of antibody levels overlapped between production systems.

Characterization and Differentiation of Chicken Mycoplasma Isolates Using 16S-23S Intergenic Spacer Region Sequencing

ABSTRACT The objective of this study was to identify the species and characterize the genetic relationships among mycoplasma isolates from commercial layer hen flocks using 16S-23S rDNA intergenic spacer region (IGSR) sequencing. Twenty-one isolates were obtained from samples collected from commercial layer flocks in four Brazilian states: Sao Paulo, Minas Gerais, Rio de Janeiro and Espirito Santo. The isolates were recovered from the Sao Paulo, Rio de Janeiro and Espirito Santo states. Eleven isolates were originated from tracheal swabs, five from shell gland swabs and five from ovary fragment collection. The 16S-23S rDNA IGSR of isolates were amplified by PCR, and the obtained products were subsequently sequenced. The consensus of each isolate was compared to the available sequences using Nucleotide BLAST® to determine the mycoplasma species. A phylogenetic analysis of the Mycoplasma gallisepticum (MG) sequences was performed. Pairwise analyses showed homologies of 99% to 100% with the previously characterized sequences listed in GenBank®. Four Mycoplasma gallinaceum were isolated from three flocks and seven M. pullorum isolates were obtained from a single flock. The other 10 isolates were all identified as MG and were obtained from four flocks. The 16S-23S rDNA IGSR sequencing was a good method to identify Mycoplasma species isolated from field samples, providing fast and reliable results at relatively low costs. The results were also satisfactory for the single-locus sequence typing of MG isolates.

Seroprevalence of Avian Reovirus Infection in Apparently Healthy Adult Commercial Layer Flocks

Seroprevalence of Avian Reovirus Infection in Apparently Healthy Adult Commercial Layer Flocks

The Seroprevalence Study of Reticuloendotheliosis Virus Infection in Chicken in Bangladesh

We showed seroprevalence of Reticuloendotheliosis virus (REV) in poultry in selected areas of Bangladesh.Total 3,555 serum samples were collected between 2014 and 2016 from 10 districts, 6 types of chicken and 144 flocks, tested for the specific antibodies directed against REV by indirect Enzyme Linked Immunosorbent Assay (ELISA). The overall seroprevalence of REV in the chickens tested were 21.13% (751/3,555) and 73.61% (106/144) flocks were seropositive. According to district, Gazipur had the highest (49.50%) and Khulna had the lowest (9.09%) seropositive rates.Additionally, the prevalence rates were highest 38.21% during onset of laying period, age between 19 and 24 weeks. The positivity rates were almost same round the year like 22.96% in summer, 20.70% in rainy and 20.43% in winter seasons.Furthermore, the seropositive rates in broiler flocks, broiler breeder flocks, commercial layer flocks, layer breeder flocks, sonali flocks, and domestic chicken flocks were 6.86%, 42.15%, 25.84%, 33.59%, 9.40%, and 6.49%, respectively. Conclusion: These results indicate that REV infections are widespread ubiquitous in all types of chickens and may appear as a potential threat for the rapidly growing poultry industry in Bangladesh. This is the first seroprevalencestudy on REV infections in chicken in Bangladesh.More prevalence study, molecular characterization and vaccine production from local isolates are emergency requirements to combat REV. The quality verification of imported vaccine must be strongly adopted.

Comparative features of infections of two Massachusetts (Mass) infectious bronchitis virus (IBV) variants isolated from Western Canadian layer flocks

BackgroundInfectious bronchitis virus (IBV) is one of the leading causes of mortality and morbidity in chickens. There are numerous serotypes and variants, which do not confer cross protection resulting in failure of currently used IBV vaccines. Although variant IBV isolates with major genetic differences have been subjected to comparative studies, it is unknown whether minor genetic differences in IBV variants within a serotype are different in terms of pathogenesis and eliciting host responses. Two Massachusetts (Mass) variant IBV isolates recovered from commercial layer flocks in the Western Canadian provinces of Alberta (AB) and Saskatchewan (SK) were compared genetically and evaluated for their pathogenicity, tissue distribution and ability to recruit and replicate in macrophages.ResultsAlthough whole genome sequencing of these two Mass IBV isolates showed low similarity with the M41 vaccinal strain, they had an identical nucleotide sequence at open reading frames (ORFs) 3a, 3b, envelop (E), matrix (M), 5a and 5b. The rest of the ORFs of these 2 IBV isolates showed 99.9% nucleotide similarity. However, upon experimental infection, we found that the IBV isolate originating from AB was different to the one that originated in SK due to higher tracheal lesion scores and lower lung viral replication and lower genome loads in cecal tonsils. Nevertheless, both IBV isolates elicited host responses characterized by significant macrophage recruitment to the respiratory tract and there was evidence that both IBV isolates replicated within tracheal and lung macrophages.ConclusionsOverall, this study shows that Mass variant IBV isolates, although possessing minor genetic variations, can lead to significant differences in pathogenicity in young chickens. Further studies are required to investigate the pathogenicity of these two Mass variant IBV isolates in laying hens.

Occurrence of infectious laryngotracheitis outbreaks in commercial layer hens detected by ELISA

ABSTRACTInfectious laryngotracheitis (ILT) is an acute respiratory disease of chickens and a cause of great economic loss in commercial layers. The aims of this study were to investigate the prevalence of ILT in the field outbreaks and to compare the characteristics of ILT-infected and free flocks of commercial layers. A total of 625 blood serum samples were collected from 25 different layer flocks. The presence of antibodies against infectious laryngotracheitis virus (ILTV) in each sample was determined by ELISA. Of the 625 serum samples, 266 (42.56%) were found to be positive for ILTV antibodies. A total of 16 (64%) flocks were detected ILT positive by ELISA method. The mortality of infected flocks was statistically higher (P < 0.05) than uninfected flocks. The egg production of positive flocks was lower than that of the free flocks, but this difference was not statistically significant. The average live weight of hens in infected flocks was lower (P > 0.05) than hens in free flocks. In conclusion, the results of this study indicated a high prevalence of ILT infection in the commercial layer flocks in Konya region, Turkey. In outbreaks, ILT significantly increased the mortality rate and decreased the average live weight in layer hens.

Antibodies to chicken anaemia virus (CAV) in poultry reared in our country

Two handred fifty eight serum samples collected from 39 poultry flocks were tested for detecting antibodies to chicken anaemia virus (CAV) by ELISA method. One handred four blood serums were collected from 11 broiler breeder flocks aged 1 day to 9,5 months, 147 from 26 broiler breeder flocks aged 1 to 45 days and 7 from 2 commercial layer flocks aged 4 in 15 days. Antibody to CAV were detected in five broiler breeder flocks aged 70 days, 2,5, 5,5, 6 and 9,5 months respectively and in 15 broiler flocks from which 2 of them aged 1 day and the other 13 flocks aged 8, 15,16, 28, 38, 42, 43 and 45 days respectively. The detection of positive serums supports our clinical observations about the presence of chicken aneamia infection principally in broiler flocks in our country.

Evaluation of immunopotentiating effect of medicinal plant products in commercial layer flock vaccinated against Newcastle disease

The present study was undertaken to evaluate the immunopotentiating effect of medicinal plant products such as Withania somnifera, Tinospora cordifolia, Allium sativum and Azadirachta indica in commercial layer flock vaccinated against Newcastle disease and production parameters. The Haemagglutination inhibition (HI) titre values in all the groups were above the protective level throughout the study period. Similar results were obtained in ELISA. The cell mediated immune response was assessed by Leukocyte Migration Inhibition Test (LMIT) and there was a significant mean per cent inhibition in treatment groups. There was no change in egg production, egg shell thickness, albumen index, Haugh unit and yolk index between treatment and control groups. In conclusion, W. Somnifera (Ashwagandha, Amukkara kizhangu), (1%), T. Cordifolia (Guduchi, Seendhil kodi), (1%), Azadirachta indica (Neem, Veembu) (0.2%) and A. Sativum (Garlic, Poondu), (0.3%) can be used as an immunostimulant in poultry against Newcastle disease vaccination without affecting the egg production and egg qualities.

Complete Genome Sequence of an Avian Metapneumovirus Subtype A Strain Isolated from Chicken (Gallus gallus) in Brazil.

ABSTRACTWe report here the complete genome sequence of an avian metapneumovirus (aMPV) isolated from a tracheal tissue sample of a commercial layer flock. The complete genome sequence of aMPV-A/chicken/Brazil-SP/669/2003 was obtained using MiSeq (Illumina, Inc.) sequencing. Phylogenetic analysis of the complete genome classified the isolate as avian metapneumovirus subtype A.

A Retrospective Study of Salmonella Enteritidis Isolated from Commercial Layer Flocks.

Consumption of shell eggs has been associated with Salmonella Enteritidis (SE) infections in humans in the United States. Because of this, the Pennsylvania Egg Quality Assurance Program (PEQAP) was developed and implemented in 1994. The PEQAP involves periodic flock testing and management practices to minimize SE contamination of shell eggs. Subsequently, the U.S. Food and Drug Administration (FDA) introduced a mandatory federal program in 2010 and 2012 for shell egg producers modeled closely after PEQAP to reduce the incidence and prevalence of SE during production, storage, and transport nationwide. In this study, a retrospective epidemiologic analysis was conducted by characterizing SE isolated from commercial layer environment samples and shell eggs submitted to the Animal Diagnostic Laboratory at The Pennsylvania State University using phage typing and pulsed-field gel electrophoresis (PFGE). The objective of this study was to determine the relatedness of SE isolates from hen house environments and shell eggs and to optimize the existing protocols of egg quality assurance programs by identifying the best layer-house environmental sampling time points in order to minimize SE contamination of shell eggs. A total of 94 SE isolates from 65 hen flocks on 35 premises in Pennsylvania recovered during 2007 to 2015 were used in this study. The SE phage type 8 and PFGE fingerprint type JEGX01.0004 most commonly associated with human SE infection was also the predominant type present in layer-house environments and shell eggs. This reconfirms hen house environmental monitoring is an effective method to identify SE-infected flocks. Further, the PEQAP program allowed SE detection of infected flocks earlier than the FDA program as it included an additional environmental test at 29-31 wk of age, enabling the earlier prevention of SE-contaminated shell eggs going to the market. Therefore, it is recommended to refine the sampling time points of the current FDA Egg Rule by adding hen house environmental testing at 29-31 wk of age.

Occurrence of necrotic enteritis in a commercial layer flock

Necrotic enteritis (NE), cause by Clostridium perfringens, is one of the leading diseases in poultry industry, which primarily affects the young chicks. The present case reports the incidence of NE in layer birds (42 weeks). The carcass was submitted for detail postmortem examination. The gross examination revealed petechial haemorrhages on intestinal mucosa and congestion in visceral organs. Microscopic observations showed degeneration and disruption of villi with haemorrhages in lamina propria and severe necrosis with submucosal haemorrhages and leucocytic infiltration in the intestine. The intestinal scrapings were collected and subsequently cultured for the isolation of causative agent. The isolates were identified as Clostridium spp. based on colony and staining characteristics, and further confirmed by detection of alpha toxin gene (402bp) using PCR.

Colonization of internal organs by Salmonella Enteritidis in experimentally infected laying hens housed in enriched colony cages at different stocking densities

Epidemiologic analyses have linked the frequency of human infections with Salmonella enterica subspecies enterica serovar Enteritidis to the consumption of contaminated eggs and thus to the prevalence of this pathogen in commercial egg-laying flocks. Contamination of the edible contents of eggs by Salmonella Enteritidis is a consequence of the colonization of reproductive tissues in systemically infected hens. The animal welfare implications of laying hen housing systems have been widely debated, but no definitive consensus has yet emerged about the food safety significance of poultry housing options. The present study sought to determine the effects of two different bird stocking densities on the invasion of internal organs by Salmonella Enteritidis in groups of experimentally infected laying hens housed in colony cages enriched with perching and nesting areas. In two trials, groups of laying hens were distributed at two different stocking densities into colony cages and (along with a group housed in conventional cages) orally inoculated with doses of 1.0 × 107 cfu of Salmonella Enteritidis. At 5 to 6 d post-inoculation, hens were euthanized and samples of internal organs were removed for bacteriologic culturing. For both trials combined, Salmonella Enteritidis was recovered at a significantly (P < 0.05) greater frequency from hens in enriched colony cages at the higher stocking density than at the lower density from livers (75.0% vs. 51.4%) and ovaries (51.4% vs. 30.6%). However, spleens from hens in enriched colony cages at the higher stocking density were significantly less often positive for Salmonella Enteritidis than from hens in conventional cages at that same density (90.3% vs. 68.1%). These results suggest that stocking density can influence the susceptibility of hens to Salmonella Enteritidis, but other housing systems parameters may also contribute to the outcome of infections.

Molecular and Serological Detection of Avian Influenza H9N2 Virus in Asymptomatic Commercial Layers in Faisalabad District, Punjab

The present study aimed at measuring the antibody titres against H9N2 influenza viruses and its molecular detections in asymptomatic commercial layers from Faisalabad district of Punjab, Pakistan. Overall 120 blood samples, 24 tissue samples from each organ (trachea, lung and intestine) were collected from the 12 commercial layer flocks selected randomly at the age of 35-50 weeks without any direct clinical manifestation of avian influenza. Serum collected from 120 birds was tested for antibodies against H9N2 by using Haemagglutination Inhibition assay. Calculated geometric mean titers of 5.37 revealed the infectivity of the flock with H9N2 Influenza virus. To investigate the presence of virus in the study population, trachea, lung and intestine tissue samples were processed for RNA isolation and subjected to molecular detection of H9 gene of H9N2 subtypes using one step Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). Out of 24 samples taken from each organ, 22, 21, and 18 samples from trachea, lungs, and intestine showed viral RNA, respectively. Taken together, results showed that the H9N2 is endemic and widely distributed in asymptotic layers. Furthermore results indicated that H9N2 subtype may survive in layers without showing any symptoms.

Atypical velogenic Newcastle disease in a commercial layer flock in Japan

In 2002, a commercial layer flock in Japan was initially diagnosed as being infected with infectious bronchitis (IB) based on clinical signs, virus isolation, and serological analysis but was later found to be atypically infected with velogenic Newcastle disease virus (NDV) following molecular diagnosis. The flock had slightly decreased egg production and an increased occurrence of soft-shelled eggs without significant mortality. IB-like viruses were isolated, which caused dwarfing and curling in 12-day-old chicken embryos. Ten years after this case, retrospective genetic analyses showed that apart from IB virus (IBV), the flock was also infected with NDV. Mean death time (MDT), intracerebral pathogenicity index (ICPI), and deduced amino acid sequence of the cleavage site of the fusion (F)-protein gene revealed that the NDV isolate was velogenic (112 RRQKR116). These results indicate that poultry clinicians should look out for atypical velogenic ND, especially in vaccinated commercial chicken flocks, which may harbor hidden NDV infection.

EPIDEMIOLOGICAL HIGHLIGHTS ON SOME VIRUSES ASSOCIATED WITH INCREASED MORTALITY IN CHICKENS BRED IN SHARKIA GOVERNORATE.

In the present study 1317 serum samples obtained from 6 broiler flocks, 2 broiler breeders and 28 commercial layer flocks were examined for HI antibodies of {NDV, IBV (Mass-41, 4/91, and D-274), AIV (H5N1, H5N2, H5N3, H9, H7) and Adenov (EDS­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­76)}. Studying the vaccination protocols in flocks under investigation and their seroconversion had led us to speculate and conclude viral affections in the different localities of Sharkia governorate. Speculating viral affections was a very hard task because the Egyptian market is jammed with a great variety of protective vaccines this was conflicting during result interpretation. Positive immune titers for AIV-H7 in sharkia governorate was detected at June /2014 in (El-salhia, 10th of Ramadan, El-ibrahemia and Abo-hammed) in commercial layer flocks only. The seropositive samples that exceeded the cutoff values were 63 out of 1317 (4.8%). AIV-H9 high seropositive immune titers was constantly found in examined samples although their protective vaccines were neglected. AIV-H5N3 seropositive results was recorded in a totally non vaccinated flocks against H5 which reflect virus circulation in the poultry premises. Seropositive titer for IBV-D274 and EDS76 was recorded in a totally non vaccinated flocks against such antigens., which refer to their role in the total simultaneous incidence of disease and consequent mortality. From another point of view it should be noted that. Vaccinating chicken flocks following a ready made manuscript of the producing companies without prior evaluation of the maternally derived antibodies (MDA) or evaluating the immune titers before taking the decision of vaccination or even considering the disease situation in the area is possible cause for vaccine failure. Sentinel birds inclusion in poultry patches should be taken seriously to give a mirror for the circulating viral agents in the poultry premises. It worth to mention that a parallel bacteriological work was running during investigation of the causes of increased mortality or dropped egg production. This work revealed the isolation of a resistant bacteria of the (Kebseilla spp).

Occurrence of infectious Laryngotracheitis Virus (ILTV) in 2009-2013 in the State of São Paulo - Brazil

Infectious laryngotracheitis is a very important respiratory disease because it causes significant economic losses in the poultry industry. The target of ILTV infections is the respiratory system, and the main organ in which the virus remains latent is the trigeminal ganglia. However, the virus has demonstrated tropism for other organs as well. The present study was conducted to determine the presence of Infectious Laryngotracheitis Virus (ILTV) in the state of São Paulo. Samples submitted to LABOR- USP during the last four years (2009-2013) analyzed by a nested/PCR technique. Out of the 682 samples from layers tested for LTIV, 12.46 % were positive, and derived from in both traditional (trachea and trigeminal ganglion) and untraditional (cecal tonsils, digestive tract and kidneys) organs utilized for ILTV diagnosis. The present work showed that ILTV is circulating in commercial layer flocks in São Paulo State, and that the LTIV is present in other organs in addition to the respiratory tract and trigeminal ganglion; however, it was not determined if the circulating virus is a vaccinal or field strain.

Antimicrobial resistance of non-typhoidal Salmonella isolates from egg layer flocks and egg shells

This study was conducted to examine the antimicrobial resistance (AMR) of Salmonella spp. isolated from commercial caged layer flocks in New South Wales and South Australia. All Salmonella isolates (n=145) were subjected to phenotypic and genotypic characterisation of AMR and carriage of integrons. The majority of Salmonella isolates (91.72%) were susceptible to all antimicrobials tested in this study. Limited resistance was observed to amoxicillin and ampicillin (5.51%), tetracycline (4.13%), cephalothin (2.06%) and trimethoprim (0.68%). None of the isolates were resistant to cefotaxime, ceftiofur, ciprofloxacin, chloramphenicol, gentamycin, neomycin or streptomycin. A low frequency of Salmonella isolates (4.83%) harboured antimicrobial resistance genes and a class 1 integron. The most commonly detected AMR genes among the Salmonella isolates were blaTEM (2.07%), tet A (1.38%) and dhfrV (0.69%). Overall, Salmonella enterica isolates exhibited a low frequency of AMR and represent a minimal public health risk associated with the emergence of multidrug resistant Salmonella spp. from the Australian layer industry.

The Prevalence and Antibiotic Susceptibilities of Thermophilic Campylobacter spp. in Commercial Layer Flocks

AMAC: Bu calismada, Bandirma’da bulunan ticari yumurtaci tavuk surulerinde termofilik Campylobacter spp. prevalansinin ve elde edilen izolatlarin degisik antibiyotiklere duyarliliklarinin belirlenmesi amaclandi. YONTEMLER: Agustos 2013-Subat 2014 doneminde, 9 adet ticari yumurtaci tavuk kumesi ziyaret edildi ve toplam 362 adet taze diski ornegi alindi. Diski orneklerinden Modified Charcoal Cefaperazone Deoxycholate Agar’a direkt ekimler yapildi ve mikroaerofilik kosullarda 42°C’de 48 saat inkube edildi. Campylobacter supheli koloniler morfolojik ve biyokimyasal karakterlerine gore identifiye edildi. Izolatlarin antibiyotiklere duyarliliklari agar disk difuzyon yontemi ile belirlendi. BULGULAR: Bakteriyolojik analiz sonucunda, 9 kumesin tamamindan (%100) ve orneklerin %39,8’inden Campylobacter spp. izolasyonu gerceklesti. Izole edilen 144 adet Campylobacter izolatinin 88’i C. jejuni (%61,1) ve 56’si C. coli (%38,9) olarak identifiye edildi. Antibiyotik duyarlilik test sonuclarina gore, C. jejuni ve C. coli izolatlarinin tetrasikline sirasiyla %46,6 ve %50 oranlarinda direncli olduklari bulundu. Florokinolonlara (siprofloksasin ve enrofloksasin) direnc oranlarinin ise sirasiyla C. jejuni izolatlarinda %62,5 ve %27,3, C. coli izolatlarinda %82,1 ve %71,4 oldugu tespit edildi. SONUC: Termofilik Campylobacter turlerinin ticari yumurtaci surulerde yuksek prevalansa sahip oldugu belirlendi. Ayrica, C. jejuni ve C. coli izolatlarinin tetrasiklin, siprofloksasin ve enrofloksasine yuksek oranda direncli olduklari tespit edildi.

Pathomorphological studies of polyserositis in commercial caged layer chicken

ObjectiveTo detect etiological agents and pathological changes associated with polyserositis in commercial layer chicken. MethodsTen commercial layer flocks which had a sudden increase in mortality and a drop in egg production with lesions suggestive of colisepticemia were investigated. Flock details and pathological changes were recorded in affected flocks to assess the prevalence and impact of polyserositis on commercial layer chicken. Trachea, heart blood, liver, oviduct, cloacal swab, poultry house environment samples, water and feed samples were screened for bacteriological agents. Pooled tissue (trachea, lung, spleen, caecal tonsil, kidney and oviduct) samples from colisepticemia cases were screened for viral agents. Serum samples collected from affected flocks were screened for Newcastle disease virus, infectious bronchitis virus and egg drop syndrome-76 virus by haemagglutination inhibition test, and for Mycoplasma gallisepticum and Mycoplasma synoviae by enzyme linked immunosorbent assay. ResultsOn necropsy examination of dead birds, fibrinous polyserositis and congestion of various visceral organs were noticed. Microscopically, deciliation and hypertrophy of mucus glands showed in the tracheal epithelium. Vascular derangements and infiltration of inflammatory cells showed in the lungs and air sac. Fibrinous polyserositis, focal necrosis and infiltration of inflammatory cells showed in parenchyma of heart and liver. Inflammatory changes were observed in the ovary and oviduct. Escherichia coli (E. coli) was isolated as a pure culture from 108 birds and from the poultry house environment of the ten affected flocks. Among the eight E. coli serotypes, identified serotypes O78 and O111 were predominant. In colisepticemia affected flocks egg production drop and mortality varied from 3%-10% and 2%-5%, respectively and occured during the peak egg production (21 to 40 weeks) and southwest monsoon season (June to September). ConclusionsThe present study revealed that the colisepticemia inducing E. coli isolates were derived from the layer house environment. Hence, the incidences of colisepticemia can be minimized by effectively reducing the bacterial load in the layer house environment through appropriate biosecurity measures.