Artificial neural networks for the management of poultry industry: a simulation based on the broiler production chain / Redes neurais artificiais para o gerenciamento da indústria avícola: uma simulação baseada na cadeia de produção de frangos de corte

The aim of this study was to predict production indicators and to determine their potential economic impact on a poultry integration system using artificial neural networks (ANN) models. Forty zootechnical and production parameters from broiler breeder farms, one hatchery, broiler production flocks, and one slaughterhouse were selected as variables. The ANN models were established for four output variables: "saleable hatching", "weight at the end of week 5," "partial condemnation," and "total condemnation" and were analyzed in relation to the coefficient of multiple determination (R2), correlation coefficient (R), mean error (E), mean squared error (MSE), and root mean square error (RMSE). The production scenarios were simulated and the economic impacts were estimated. The ANN models were suitable for simulating production scenarios after validation. For "saleable hatching", incubator and egg storage period are likely to increase the financial gains. For "weight at the end of the week 5" the lineage (A) is important to increase revenues. However, broiler weight at the end of the first week may not have a significant influence. Flock sex (female) may influence the "partial condemnation" rates, while chick weight at first day may not. For "total condemnation", flock sex and type of chick may not influence condemnation rates, but mortality rates and broiler weight may have a significant impact.

O objetivo deste trabalho foi predizer os indicadores de produção e determinar o seu potencial impacto econômico em um sistema de integração utilizando as redes neurais artificiais (RNA). Quarenta parâmetros zootécnicos e de produção de granjas de matrizes e de frango de corte, um incubatório e um abatedouro foram selecionados como variáveis. Os modelos de RNA foram estabelecidos para quatro variáveis de saída ("eclosão vendável", "peso ao final da quinta semana", "condenações parciais" e "condenações totais") e foram analisados em relação ao coeficiente de determinação múltipla (R2), coeficiente de correlação (R), erro médio (E), erro quadrático médio (EQM) e raiz do erro quadrático médio (REQM). Os cenários produtivos foram simulados e os impactos foram estimados. Os modelos de RNA gerados foram adequados para simular diferentes cenários produtivos após o treinamento. Para "eclosão vendável", o modelo de incubadora e o período de incubação aumentaram os ganhos financeiros. Para "peso ao final da quinta semana", a linhagem também demonstrou influencia no retorno financeiro, o que não aconteceu com o peso ao final da primeira semana. O sexo do lote possui influência nas taxas de "condenação parcial", ao contrário do peso do frango no primeiro dia. As taxas de mortalidade e o peso do frango apresentaram influência na "condenação total", mas o sexo do lote e o tipo de pinto não tiverem influência.

Cutaneous myxoma in broiler chicken detected during slaughtering

Background: A cutaneous or superficial myxoma is a benign neoplasm of dermal or subcutaneous fibroblast origin. Although rare, it has been previously described in several species, including poultry. It presents as a single node or soft mass with a gelatinous cut surface. Histopathological analysis is essential for diagnosis and to differentiate it from other mesenchymal neoplasms and inflammatory or degenerative processes. Microscopically, it consists of dermal or subcutaneous lobules of plump, stellate, or spindle-shaped, bland-looking cells embedded in a basophilic myxoid matrix. This report describes the pathological findings in a rare case of cutaneous myxoma in a 42-day-old broiler flock. Cases: During ante mortem inspection of a 42-day-old broiler flock at a slaughterhouse under the authority of the Federal Inspection Service (southern Brazil), nodular lesions or encrusted areas with yellow and black areas were observed in the head skin of less than 1% of animals. These lesions, approximately 0.5 cm in diameter, were observed on the comb, in the periocular skin region, and close to the animals' nostrils. During the breeding period, no health or epidemiological events were observed. Fragments of the lesions in the comb and periocular skin were collected and fixed in buffered 10% formalin. The samples were sent to the laboratory, routinely processed, and stained with hematoxylin and eosin and Alcian blue. Microscopically, the lesions consisted of irregular multifocal proliferation of connective tissue showing spindle cells with poorly demarcated borders and scarce cytoplasm in a slightly basophilic myxoid aspect matrix. The adjacent epidermis is compressed due to neoplastic proliferation. No areas of epithelial hyperplasia or inclusion bodies were observed. According to the pathologic description and considering its descriptive epidemiology, our main clinical suspicion was cutaneous fowl pox, a pathology characterized by the appearance of nodules in regions devoid of feathers. However, the microscopic changes observed were compatible with those described for cutaneous myxomas. In addition, the extracellular matrix was positive for Alcian Blue staining, which is an indicator of myxoma. In the present case, the SIF did not report the same macroscopic lesions in other flocks of the same origin. Discussion: Connective tissue tumors, including myxomas, occur considerably less frequently under field conditions. In addition, these neoplasms are more frequent in mature birds and are not usually described in broilers, as observed in this report. The cutaneous myxoma described in broilers is usually a sporadic neoplasm that does not cause zootechnical losses, as observed in the case report. Its etiology is unknown and has been associated with various factors, such as local trauma and foreign bodies. Some fragments of plant material from the breeding environment were microscopically detected in the encrusted areas, which may indicate previous trauma or a foreign body. Myxoma has been associated with avian leukosis virus (ALV) subgroup A, but SIF did not report the same macroscopic lesions in other flocks of the same breeder hen's origin in the present case. Furthermore, sporadic connective tissue tumors associated with the virus occur in mature chickens but not in broilers. Myxoma lesions should be considered in the differential diagnosis of other connective tissue tumors and infectious agents that cause lesions in the skin and subcutaneous tissue.

Identification of Virulence-Associated Markers in Escherichia Coli Isolated from Captive Red-Browed Amazon Parrot (Amazona Rhodocorytha)

Due to the genetic similarity of pathogenic Escherichia coli isolated from birds and pathotypes of human origin, it is suggested that they have a common ancestor and may exchange virulence-associated genes. This study aimed to detect virulence-associated genes in E. coli strains isolated from the Red-browed Amazon parrot (Amazona rhodocorytha) kept at a conservation institute in Brazil. High genetic variability in virulence was observed, since 12 virulence profiles were found among 14 strains. The number of virulence-associated genes of single strains ranged from 5 to 22 out of 33 genes tested, and only one strain did not present any virulence genes. Regarding adhesion genes, most strains presented from two to five genes, and crlA (85.7%) and fimC (85.7%) were the most frequent. Frequencies were similar for invasion and iron acquisition genes. Variations among genes were observed for serum resistance and toxin-related genes. Some of the E. coli strains isolated from parrots presented virulence genes that are commonly associated with pathotypes of human origin, including newborn meningitis E. coli, uropathogenic E. coli, and sepsis-associated E. coli. It is noteworthy that some of these genes were present in the majority of the analyzed strains. Our results indicate that these strains detected in clinically healthy parrots can be potential reservoirs of several virulence-associated genes. These genes can be transmitted to other E. coli strains, including those that affect humans. These E. coli strains present a high pathogenic potential of virulence-associated genes in extraintestinal pathogenic E. coli strains.(AU)

Development of copper hatch baskets and evaluation of the productive indexes of a commercial hatchery

Background: The dissemination of pathogenic microorganisms in hatcheries leads to a higher number of contaminated eggs, causing reduction in hatchability and increase of discarded chicks. Sanitation programs are crucial for maximum hatchability and chick quality. Efforts have been made to find alternative approaches to the conventional disinfectants, and surfaces with copper, which have antimicrobial properties, could assist in this process. However, the possible adverse effects of copper surfaces on chicks in hatcheries have not yet been evaluated. The present study aimed at developing hatch baskets composed of copper and evaluating the effect of these baskets on the productive indexes of a hatchery. Materials, Methods & Results: For this experiment, 3.15 kg hatch tray prototypes with 99.9% Cu (Cu11000) were developed to fit inside conventional polypropylene hatch baskets (580 × 755 × 83 mm). Six polypropylene hatch baskets (control group) and six polypropylene hatch baskets covered by 99.9% copper (Cu11000) hatch trays (test group) were evaluated during 5 hatchings. Hatched eggs and chicks remained in contact with the hatch basket surfaces for at least 72 h, corresponding to the entire period in which they were located in the hatcher. Cleaning and disinfection programs of the hatchery were not modified. The level of microbial contamination on the hatch baskets was evaluated at 6 different periods: 0 h (initial contamination after disinfection and egg transfer to the trays); 24 h, 30 h, 45 h and 60 h after the first sampling; and at the moment when chicks were removed from the hatching cabinet and transferred to the chick-holding room (> 60 h). Counting of total moulds and yeasts, mesophilic microorganisms, Enterobacteria and Escherichia coli colonies was performed. The number of hatched chicks, non-hatched eggs, and chicks discarded were registered for each hatching. Microbiologic analyses showed no growth on hatch baskets neither of the..

Artificial neural networks on eggs production data management

Background: Eggs have acquired a greater importance as an inexpensive and high-quality protein. The Brazilian eggindustry has been characterized by a constant production expansion in the last decade, increasing the number of housedanimals and facilitating the spread of many diseases. In order to reduce the sanitary and financial risks, decisions regarding the production and the health status of the flock must be made based on objective criteria. The use of Artificial NeuralNetworks (ANN) is a valuable tool to reduce the subjectivity of the analysis. In this context, the aim of this study was atvalidating the ANNs as viable tool to be employed in the prediction and management of commercial egg production flocks.Materials, Methods & Results: Data from 42 flocks of commercial layer hens from a poultry company were selected. Thedata refer to the period between 2010 and 2018 and it represents a total of 600,000 layers. Six parameters were selectedas “output” data (number of dead birds per week, feed consumption, number of eggs, weekly weight, weekly egg production and flock uniformity) and a total of 13 parameters were selected as “input” data (flock age, flock identification, totalhens in the flock, weekly weight, flock uniformity, lineage, weekly mortality, absolute number of dead birds, eggs/hen,weekly egg production, feed consumption, flock location, creation phase). ANNs were elaborated by software programsNeuroShell Predictor and NeuroShell Classifier. The programs identified input variables for the assembly of the networksseeking the prediction of the variables called outgoing that are subsequently validated. This validation goes through thecomparison between the predictions and the real data present in the database that was the basis for the work. Validation ofeach ANN is expressed by the specific statistical parameters multiple determination (R2) and Mean Squared Error...

Artificial neural networks on eggs production data management

Background: Eggs have acquired a greater importance as an inexpensive and high-quality protein. The Brazilian eggindustry has been characterized by a constant production expansion in the last decade, increasing the number of housedanimals and facilitating the spread of many diseases. In order to reduce the sanitary and financial risks, decisions regarding the production and the health status of the flock must be made based on objective criteria. The use of Artificial NeuralNetworks (ANN) is a valuable tool to reduce the subjectivity of the analysis. In this context, the aim of this study was atvalidating the ANNs as viable tool to be employed in the prediction and management of commercial egg production flocks.Materials, Methods & Results: Data from 42 flocks of commercial layer hens from a poultry company were selected. Thedata refer to the period between 2010 and 2018 and it represents a total of 600,000 layers. Six parameters were selectedas “output” data (number of dead birds per week, feed consumption, number of eggs, weekly weight, weekly egg production and flock uniformity) and a total of 13 parameters were selected as “input” data (flock age, flock identification, totalhens in the flock, weekly weight, flock uniformity, lineage, weekly mortality, absolute number of dead birds, eggs/hen,weekly egg production, feed consumption, flock location, creation phase). ANNs were elaborated by software programsNeuroShell Predictor and NeuroShell Classifier. The programs identified input variables for the assembly of the networksseeking the prediction of the variables called outgoing that are subsequently validated. This validation goes through thecomparison between the predictions and the real data present in the database that was the basis for the work. Validation ofeach ANN is expressed by the specific statistical parameters multiple determination (R2) and Mean Squared Error...(AU)

Characterization of immune and enteric systems of broilers after imunosupression with dexamethasone

Background: Bursa of Fabricius (BF) and the thymus are primary lymphoid organs of poultry and play a major role in avian immunity. Enteric system is also involved in immunity. Several pathologic conditions directly impact BF and thymus size, and also affect intestinal parameters. Besides, there are several immune system depressor agents which affect birds. The selection of glucocorticoid as inducer of immunosuppression is applied in many experiments; however there are few studies that are applied to the reality in the field. In this context, the aim of this study was to evaluate the effects of dexamethasone as an inducer of immunosuppression on lymphoid organs and microscopic structures of the jejunum.Materials, Methods & Results: One-day-old chicks were used as a control group (n = 8) and the treated group (n = 25) received intramuscular dexamethasone on 21, 23, 24 and 26 day-old. Control birds and treated birds were euthanized 8, 16, 24, 32 and 40 h after inoculation; four control birds and six treated birds were euthanized on the eighth day after the last inoculation. Thymus, BF and jejunum were collected during the necropsy. The selected organs were processed, stained with hematoxylin and eosin and photographed. The BF and thymus cuts were evaluated by three histopathologists to determine the depletion score. Ten villi of each jejunum were evaluated for width and length of villi, depth crypt, microvillus length, enterocyte length of each villus, and wall thickness. Treated birds presented a mean weight lower than control group during all the experiment. The mean weight and the relative weight of the BF and thymus of control birds were significantly higher than treated ones. The lymphocyte depletion in BF and thymus scores differed significantly between groups, being higher in the group challenged with dexamethasone. There were no significant differences between groups for depth of crypt, height of core and height of microvilli.[...]

Characterization of immune and enteric systems of broilers after imunosupression with dexamethasone

Background: Bursa of Fabricius (BF) and the thymus are primary lymphoid organs of poultry and play a major role in avian immunity. Enteric system is also involved in immunity. Several pathologic conditions directly impact BF and thymus size, and also affect intestinal parameters. Besides, there are several immune system depressor agents which affect birds. The selection of glucocorticoid as inducer of immunosuppression is applied in many experiments; however there are few studies that are applied to the reality in the field. In this context, the aim of this study was to evaluate the effects of dexamethasone as an inducer of immunosuppression on lymphoid organs and microscopic structures of the jejunum.Materials, Methods & Results: One-day-old chicks were used as a control group (n = 8) and the treated group (n = 25) received intramuscular dexamethasone on 21, 23, 24 and 26 day-old. Control birds and treated birds were euthanized 8, 16, 24, 32 and 40 h after inoculation; four control birds and six treated birds were euthanized on the eighth day after the last inoculation. Thymus, BF and jejunum were collected during the necropsy. The selected organs were processed, stained with hematoxylin and eosin and photographed. The BF and thymus cuts were evaluated by three histopathologists to determine the depletion score. Ten villi of each jejunum were evaluated for width and length of villi, depth crypt, microvillus length, enterocyte length of each villus, and wall thickness. Treated birds presented a mean weight lower than control group during all the experiment. The mean weight and the relative weight of the BF and thymus of control birds were significantly higher than treated ones. The lymphocyte depletion in BF and thymus scores differed significantly between groups, being higher in the group challenged with dexamethasone. There were no significant differences between groups for depth of crypt, height of core and height of microvilli.[...](AU)

Classificação de Escherichia coli patogênica aviária (APEC)e de Escherichia coli uropatogênica (UPEC) em grupos filogenéticose associação com a patogenicidade in vivo / Classification of Avian Pathogenic Escherichia coli (APEC) and Human Uropathogenic Escherichia coli (UPEC) in phylogenetic groups and association with pathogenicity in vivo

Background: Avian pathogenic E. coli (APEC) and uropathogenic E. coli (UPEC) are responsible, respectively, for avian colibacillosis and for 80% of urinary tract infections in humans. E. coli control is difficult due to the absence of a reliable method to differentiate pathogenic and commensal strains. Genetic similarity between APEC and UPEC suggests a common ancestral origin and the capability of potentially pathogenic strains to affect human health. The classification in phylogenetic groups facilitates the identification of pathogenic strains. The objective of this work was to classify APEC and UPEC E. coli strains into phylogenetic groups and to associate it with in vivo pathogenicity. Materials, Methods & Results: 460 APEC and 450 UPEC strains, stored in BHI with glycerol at -80°C, were selected. APEC strains were isolated from cellulitis, respiratory tract and poultry litter of broiler flocks from Southern Brazil. The UPEC strains from urinary tract infection were provided by a hospital in Porto Alegre. After DNA extraction, APEC and UPEC strains were classified into four phylogenetic groups (A, B1, B2 and D) by a multiplex-PCR protocol for the detection of the chuA and yjaA genes and the TspE4.C2 DNA fragment. Phylogenetic groups were associated with pathogenicity indexes (PI), presented on a scale of 0 to 10, which were previously obtained through the inoculation of APEC strains in one-day-old chicks. Phylogenetic groups were also associated with the presence of 38 virulence-associated genes. The multiplex-PCR protocol was able to differentiate 100% of the APEC and UPEC strains in the four phylogenetic groups. The majority of APEC strains were classified into phylogenetic groups D (31.1%) and B2 (24.1%). On the other hand, the majority of UPEC strains were classified into B2 (53.6%). Among APEC strains, five genes (crl, mat, ompA, fimC and fimH) […](AU)

Classificação de Escherichia coli patogênica aviária (APEC)e de Escherichia coli uropatogênica (UPEC) em grupos filogenéticose associação com a patogenicidade in vivo / Classification of Avian Pathogenic Escherichia coli (APEC) and Human Uropathogenic Escherichia coli (UPEC) in phylogenetic groups and association with pathogenicity in vivo

Background: Avian pathogenic E. coli (APEC) and uropathogenic E. coli (UPEC) are responsible, respectively, for avian colibacillosis and for 80% of urinary tract infections in humans. E. coli control is difficult due to the absence of a reliable method to differentiate pathogenic and commensal strains. Genetic similarity between APEC and UPEC suggests a common ancestral origin and the capability of potentially pathogenic strains to affect human health. The classification in phylogenetic groups facilitates the identification of pathogenic strains. The objective of this work was to classify APEC and UPEC E. coli strains into phylogenetic groups and to associate it with in vivo pathogenicity. Materials, Methods & Results: 460 APEC and 450 UPEC strains, stored in BHI with glycerol at -80°C, were selected. APEC strains were isolated from cellulitis, respiratory tract and poultry litter of broiler flocks from Southern Brazil. The UPEC strains from urinary tract infection were provided by a hospital in Porto Alegre. After DNA extraction, APEC and UPEC strains were classified into four phylogenetic groups (A, B1, B2 and D) by a multiplex-PCR protocol for the detection of the chuA and yjaA genes and the TspE4.C2 DNA fragment. Phylogenetic groups were associated with pathogenicity indexes (PI), presented on a scale of 0 to 10, which were previously obtained through the inoculation of APEC strains in one-day-old chicks. Phylogenetic groups were also associated with the presence of 38 virulence-associated genes. The multiplex-PCR protocol was able to differentiate 100% of the APEC and UPEC strains in the four phylogenetic groups. The majority of APEC strains were classified into phylogenetic groups D (31.1%) and B2 (24.1%). On the other hand, the majority of UPEC strains were classified into B2 (53.6%). Among APEC strains, five genes (crl, mat, ompA, fimC and fimH) […]

Virulence genes and antimicrobial resistance of Pasteurella multocida isolated from poultry and swine

Pasteurella multocida causes atrophic rhinitis in swine and fowl cholera in birds, and is a secondary agent in respiratory syndromes. Pathogenesis and virulence factors involved are still poorly understood. The aim of this study was to detect 22 virulence-associated genes by PCR, including capsular serogroups A, B and D genes and to evaluate the antimicrobial susceptibility of P. multocida strains from poultry and swine. ompH, oma87, plpB, psl, exbD-tonB, fur, hgbA, nanB, sodA, sodC, ptfA were detected in more than 90% of the strains of both hosts. 91% and 92% of avian and swine strains, respectively, were classified in serogroup A. toxA and hsf-1 showed a significant association to serogroup D; pmHAS and pfhA to serogroup A. Gentamicin and amoxicillin were the most effective drugs with susceptibility higher than 97%; however, 76.79% of poultry strains and 85% of swine strains were resistant to sulphonamides. Furthermore, 19.64% and 36.58% of avian and swine strains, respectively, were multi-resistant. Virulence genes studied were not specific to a host and may be the result of horizontal transmission throughout evolution. High multidrug resistance demonstrates the need for responsible use of antimicrobials in animals intended for human consumption, in addition to antimicrobial susceptibility testing to P. multocida. (AU)

Classification of avian pathogenic Escherichia coli by a novel pathogenicity index based on an animal model

Background: Avian Pathogenic Escherichia coli is the main agent of colibacillosis, a systemic disease that causes considerable economic losses to the poultry industry. In vivo experiments are used to measure the ability of E. coli to be pathogenic. Generally, these experiments have proposed different criteria for results interpretation and did not take into account the death time. The aim of this study was to propose a new methodology for the classification of E. coli pathogenicity by the establishment of a pathogenicity index based in the lethality, death time and the ability of the strain to cause colibacillosis lesions in challenged animals. Materials, Methods & Results: A total of 293 isolates of E. coli were randomly selected to this study. The strains were isolated from cellulitis lesions, broiler bedding material or respiratory diseases and were previously confirmed through biochemical profile. The bacterial isolates were kept frozen at -20C. The strains were retrieved from stocks and cultured in brain-heart infusion broth overnight at 37C to obtain a final concentration of 109 UFC/mL. A total of 2940 one-dayold chicks from commercial breeding hens were randomly assigned to groups containing 10 animals and each group was subcutaneously inoculated in the abdominal region with 0.1 mL of the standard inoculum solution containing each of the strains. A control group [...](AU)

Classification of avian pathogenic Escherichia coli by a novel pathogenicity index based on an animal model

Background: Avian Pathogenic Escherichia coli is the main agent of colibacillosis, a systemic disease that causes considerable economic losses to the poultry industry. In vivo experiments are used to measure the ability of E. coli to be pathogenic. Generally, these experiments have proposed different criteria for results interpretation and did not take into account the death time. The aim of this study was to propose a new methodology for the classification of E. coli pathogenicity by the establishment of a pathogenicity index based in the lethality, death time and the ability of the strain to cause colibacillosis lesions in challenged animals. Materials, Methods & Results: A total of 293 isolates of E. coli were randomly selected to this study. The strains were isolated from cellulitis lesions, broiler bedding material or respiratory diseases and were previously confirmed through biochemical profile. The bacterial isolates were kept frozen at -20C. The strains were retrieved from stocks and cultured in brain-heart infusion broth overnight at 37C to obtain a final concentration of 109 UFC/mL. A total of 2940 one-dayold chicks from commercial breeding hens were randomly assigned to groups containing 10 animals and each group was subcutaneously inoculated in the abdominal region with 0.1 mL of the standard inoculum solution containing each of the strains. A control group [...]

A sensitive nested-Polymerase Chain Reaction protocol to detect infectious laryngotracheitis virus

Background: Infectious laryngotracheitis virus (ILTV) is a member of the family Herpesviridae that has a worldwide distribution, although it is well controlled in areas of intensive production in which periodic outbreaks of the disease occur. ILTV is an important respiratory pathogen of chickens that may cause severe or mild disease in layers and broilers. Severe disease is characterized by respiratory depression, gasping, expectoration of bloody exudate and high mortality. Mild diseased chickens exhibit milder clinical signs and low mortality, and laboratory techniques are mandatory for a final diagnosis. Several techniques have been described for the detection of ILTV, however they have disadvantages that constrains their use in routine diagnosis. Viral multiplication is limited to respiratory tissue, which makes the trachea the ideal site to look for the virus. The purpose of the present study was to develop a sensitive and specific nested Polymerase Chain Reaction (PCR) protocol to detect ILTV DNA directly from tracheal swabs of naturally or experimentally infected chickens. Materials, Methods & Results: The nested-PCR was carried out with two sets of primers selected from a portion of the ILTV thymidine kinase gene. PCR sensitivity was determined by using five-fold serial dilutions of a commercial laryngotracheitis vaccine. PCR was specific as determined by testing related respiratory viruses (pathogens of chickens), ILTV strain, and field isolates. Nested-PCR was 250 times more sensitive than virus isolation (VI). To further validate the ability of this assay to detect ILTV from tracheal swabs, experimentally infected chickens and ILTV suspect cases were examined by VI, PCR, and histopathology. VI and nested-PCR both detected virus in tracheas during all the experimental period. With one exception, all positive samples by VI were also positive by the nested-PCR. However, nested-PCR detected 5 additional positive samples in the end of the experimental period. Through direct histopathology, typical syncytia and inclusion bodies were found in only two samples. In the clinical cases of respiratory illness, VI detected ILTV positive samples in 4 out of the 8 flocks with respiratory illness and histopathological analyses detected 3 flocks but the nested-PCR detected 5 positive fl ocks including those positive by VI and histopathology. Discussion: In the experimental infection, VI and PCR both detected ILTV in the majority of the samples but PCR detected some additional positive samples close to the end of the experimental period. By comparison of the PCR with VI sensitivity, it can be concluded that the protocol here described has a greater advantage over the previously described protocols that afford a direct comparison. Histopathology was the least sensitive test, since viral inclusion bodies and syncytial cells were only observed in two tracheal sections and a possible explanation for this result may be that necrosis and desquamation destroy infected epithelium. In the detection of the virus from clinical cases, the nested-PCR also detected a greater number of positive samples than VI and histopathology. Comparison of the nested-PCR with VI in experimentally infected broilers indicates that the two diagnostic tests are very efficient to detect ILTV in the early time of infection. However, VI tests in late infection may be not as sensitive as the nested-PCR if majority of the ILTV have been inactivated or become latent. Two distinctive sequences were obtained from the positive controls and field isolates. The sequences were specific to ILTV since they had a minimum of 99.5% similarity with previously described strains. The assay described in the present study indicates that the nested-PCR protocol is more sensitive than previously described tests and can replace histopathology and virus isolation with advantage.

Detecção do vírus da laringotraqueíte das galinhas no Brasil / Detection of infectious laryngotracheitis virus in chickens in Brazil

O propósito deste estudo foi detectar a presença do vírus da laringotraqueíte infecciosa (VLTI) das galinhas em algumas granjas do Brasil. Tecidos da traquéia e suabes foram coletados de 10 lotes de frangos de corte e galinhas de postura com sinais respiratórios. O material foi inoculado em ovos embrionados e as membranas corioalantóides examinadas por histopatologia. Além disso, as amostras foram submetidas à reação em cadeia da polimerase (PCR). Três lotes foram positivos para VLTI por isolamento viral e PCR. Os resultados confirmam a presença do VLTI nas galinhas no Brasil. (AU)

A study was carried out in search for evidences of infectious laryngotracheitis virus (ILTV) infections in some Brazilian chicken flocks. Tracheal tissues and swabs were collected from 10 different flocks of layers and broilers displaying respiratory signs of disease. Samples were processes for virus isolation in embryonated eggs and the membranes examined by histopathology. In addition, specimens were examined by polymerase chain reaction (PCR). Three flocks had ILTV positive chickens by virus isolation and PCR. These results confirm the occurrence of ILTV in chickens in Brazil. (AU)

Laryngotracheitis: reproducibility of the disease and comparison of diagnostic methods

Infectious laryngotracheitis virus (ILTV) cause mild to severe respiratory disease in chickens, the purpose of our study being to use Brazilian isolate of ILTV to reproduce ILTV disease in chickens by experimental infection and to compare three diagnostic methods (nested polymerase chain reaction (PCR), virus isolation, histopathology) for detection of ILTV. Forty-eight chickens intratracheally inoculated with ILTV and a further 48 with PBS, showing mild respiratory signs 48 hours post infection (PI) but no signs of infection after day 10 PI. Every 2 days PI, six birds were arbitrarily selected from the control and infected groups, sacrificed and the trachea collected. Both the nested PCR and virus isolation detected the virus from day 2 until day 12 PI. However, at day 12 PI, PCR detected ILTV DNA in 100% of the samples while the virus isolation method detected ILTV in only 33% of the samples. Tracheal histopathology showed intranuclear inclusion bodies on days 8 and 10 PI. The results indicate that the field-isolate of ILTV studied by us is of low pathogenicity and that our nested PCR protocol was able to detect positive samples over a longer infection period than many ILTV diagnostic test already described.

O vírus da laringotraqueíte (VLT) causa de leve a severa doença respiratório em galinhas, o propósito do nosso estudo foi usar um isolado brasileiro de VLT para reproduzir a doença em frangos através da infecção experimental e comparar três métodos de diagnóstico (nested PCR, isolamento viral e histopatologia) para detectar o VLT. Quarenta e oito frangos inoculados intratraquealmente com VLT e outros 48 com PBS, apresentaram sinais respiratórios leves 48 horas após a infecção (PI), mas nenhum sinal após o dia 10 PI. A cada dois dias, seis aves foram selecionados arbitrariamente do controle e do grupo infectado, sacrificados e as traquéias coletadas. Ambos nested PCR e isolamento viral detectaram o vírus do dia 2 até o dia 12 PI. No entanto, no dia 12 PI, a PCR detectou o DNA viral em 100% das amostras enquanto o isolamento viral detectou em somente 33% das amostras. Histopatologia da traquéia revelou corpúsculos de inclusão intranuclear nos dias 8 e 10 PI. Os resultados indicam que o VLT isolado de campo estudado é de baixa patogenicidade e que o protocolo de Nested PCR foi capaz de detectar amostras positivas por um período mais longo da infecção do que muitos testes de diagnósticos descritos.