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Thesis (Ph. D.)--Mississippi State University. Department of Poultry Science. / Title from title screen. Includes bibliographical references.

Mycoplasma gallisepticum (MG) is a bacterium that causes egg production losses in layer chickens raised on multi-age layer hen complexes. To combat this loss, layer chickens are vaccinated against MG before they are moved to the layer facility to begin laying eggs. The objective of this dissertation research was to investigate the potential of the in ovo vaccination of layer chickens against field strain MG infections to enhance immunity, and reduce labor and material costs associated with the current post-hatch vaccination method. Initial studies tested various dosages of a live attenuated strain F (FMG) vaccine delivered in ovo by hand injection at 18 days of incubation. The greatest dilution of vaccine (1-3 colony forming units (CFU) per dose) did not have an adverse effect on hatch success and was able to induce initial antibody production against FMG in approximately 50% of the birds raised through 6 weeks of age, with relatively low post-hatch mortality. Higher dosages tested, starting at 102 CFU per dose, caused extremely high (>50%) post-hatch mortality during the first 2 weeks and were considered impractical. These in ovo-vaccinated birds, even at the lowest FMG dose, were able to transmit the bacteria to other MG-clean birds with which they were in direct contact. The lowest in ovo FMG dose was further tested for its ability to be applied using a current in ovo vaccination machine. This machine externally disinfects each injection needle after every injection. The FMG was detected in FMG-vaccinated birds at 6 weeks of age whether or not they had received the disinfection step. Furthermore, birds hatched from eggs that were injected with and without disinfection had comparable humoral immune responses against FMG, with similar results to the hand injection study. Thus, the disinfection step during in ovo vaccination caused no loss of FMG vaccine efficiency and the in ovo vaccination of layer chickens against FMG could be readily practiced in the poultry industry. Future work should evaluate how this in ovo vaccination regimen compares with other post-hatch MG vaccination regimens for layer chickens through the lay cycle and against a field strain MG challenge.

Mycoplasma gallisepticum (MG) is a major and economically significant pathogen of avian species. Different strains of MG have been used as vaccines in multiple-age commercial layer farms in an effort to protect the birds against more virulent field strains. The lower level of protection afforded by the low virulent MG strain vaccines provides an opportunity to the use of an overlay (revaccination) with an F-strain M. gallisepticum (FMG) later in their production cycles. In the present study, three trials were conducted to investigate the effects of prelay vaccinations of ts-11 strain MG, MG-Bacterin, or their combination, in conjunction with a FMG overlay after peak production in commercial layers. The following treatments were utilized at 10 wk of age (woa): 1) Control (no vaccinations); 2) ts-11 MG vaccine; 3) MG-Bacterin vaccine; and 4) ts-11 MG and MG-Bacterin combination. At 45 woa, all the birds in trial 1 and half of the birds in each treatment group in trials 2 and 3 were overlaid with an FMG vaccine. Various parameters including performance, internal egg and eggshell quality, blood, and visceral characteristics of the birds were evaluated. In this study, the ts-11 MG vaccination at 10 woa was shown to increase shell weight and the yolk lipid content of the eggs laid by the birds without affecting their performance. On the other hand, a prelay vaccination with MG-Bacterin did not prevent a drop in egg production in response to an overlay with FMG at 45 woa. A decrease in proportional infundibulum length in the control birds and MG-Bacterin vaccinated birds after being overlaid with FMG might be the underlying factor responsible for the observed decrease in egg production. Nevertheless, the prelay use of MG-Bacterin together with ts-11 MG didn’t appear to provide any additional benefit over the ts-11 MG vaccine alone on any of the parameters investigated. In conclusion, these results establish the potentially effective prelay use of the ts-11 MG vaccine in combination with an FMG overlay for the provision of continual protection against field strain MG infections, without eliciting any subsequent suppressive effects on the performance of commercial layers.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Includes bibliographic references (p.74-92).

Memoria para optar al Título Profesional de Médico Veterinario. / Se recolectaron 453 muestras de suero de gallinas ponedoras pertenecientes a una empresa productora de huevos ubicada en la Región de Valparaíso, y se determinó la seroprevalencia de Mycoplasma gallisepticum (MG) y Mycoplasma synoviae (MS) a través de la detección de anticuerpos utilizando la prueba de ensayo por inmunoabsorción ligado a enzimas (ELISA). Las muestras se obtuvieron desde los 10 sectores con aves de diferentes edades pertenecientes a las 4 granjas que componen la empresa, y se evidenció que todos éstos presentaron individuos positivos a MG y/o MS. Del total de las 453 muestras de sueros, se observó que 239 (52,8%) eran positivas a MG, mientras que 322 (71,1%) eran positivas a MS. Los rangos de positividad fluctuaron entre un 6,7% y un 100% tanto para MG como para MS en los distintos sectores evaluados. Para ambos agentes se evaluaron diferencias en los factores grupo etario, tipo de galpón, granja y sector productivo. En el caso de MG, la granja Los Ceibos, los sectores Ceibo 1, Ceibo 2 y Ceibo 3, y los galpones abiertos, fueron los que mostraron una mayor cantidad de muestras positivas. Mientras que para MS, la granja Los Ceibos, los sectores Ceibo 1, Ceibo 3, Los Boldos y Los Espinos, los galpones abiertos y los grupos etarios de mediana y avanzada edad fueron los que mostraron una mayor cantidad de muestras positivas. / 453 serum samples from laying hens belonging to an egg producer located in the Valparaíso region were collected to determine the seroprevalence of Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) by using the enzyme-linked immunosorbent assay (ELISA). The samples were obtained from 10 sectors of the company, which had birds of different ages belonging to the company 4 farms. It was shown that all these sectors have positive MG and / or MS birds. Of the total of 453 serum samples 239 (52.8%) were positive to MG, while 322 (71.1%) were positive to MS. The ranges of positivity ranged between 6.7% and 100% for both MG and MS in the different sectors evaluated. Differences in certain factors were evaluated for both agents: age, type of barn, farm and production sector. For MG, the farm Los Ceibos, the Ceibo 1 sector, Ceibo 2 sector, Ceibo 3 sector and open sheds showed a greater number of positive samples. For MS, the farm Los Ceibos, the Ceibo 1 sector, Ceibo 3 sector, Los Boldos sector, Los Espinos sector, open sheds and the age groups of middle and old age were those who had a higher number of positive samples.

Vaccination programs using live whole cell vaccines are presently being used to control outbreaks and to help protect flocks from field strains of Mycoplasma gallisepticum. The primary goal of the present study was to investigate the effects of a ts11-strain M. gallisepticum inoculation alone, and in conjunction with F-strain M. gallisepticum overlays at 22 or 45 weeks of age during lay. In this study, it was shown that a pre-lay ts11 vaccination had a broad range effect on the physiology of the commercial layer without affecting overall performance. The timing of an overlay vaccination using F-strain M. gallisepticum during lay also had varied effects on physiological parameters without affecting overall performance. This study indicates that using ts-11-strain M. gallisepticum in conjunction with F-strain M. gallisepticum does not negatively affect laying hen performance. Furthermore, this inoculation combination offers benefits above the use of those achieved through either inoculation alone

For 36 generations, White Leghorn chickens were selected for high (HAS) or low (LAS) antibody response to sheep red blood cells. The focus of this thesis was to investigate correlated responses in reproductive soundness and egg quality resulting from that selection. Forty-five hens and 25 roosters from each antibody line were used. In hens, commencement and intensity of lay, and egg quality, were analyzed; in both sexes, length of fertility was considered. Hens and roosters were mated to an intercross line to avoid confounding selection with sex effects. The LAS line was more reproductively sound, commencing lay at a younger age (11.67 ± 3.53 d; P < 0.001), lighter body weight (-169.46 ± 40.20 g; P < 0.001) and with greater intensity (2.68 ± 0.25%; P = 0.001) than the HAS line. Additionally, the LAS line had a greater length of fertility (hens: 2.43 ± 0.55 d; P < 0.001; roosters: 3.11 ± 0.71 d; P < 0.001). In contrast to their poorer reproductive soundness, the HAS line had superior egg quality compared to the LAS line. Egg shape index (4.12 ± 0.55; P < 0.001) and albumen height, measured in both mm (0.27 ± 0.12 mm; P < 0.001) and Haugh units (1.89 ± 0.91; P = 0.04), were superior in HAS hens. Selection for increased antibody response appeared to compromise reproductive soundness, perhaps due to limitations in available resources. However, the selection did not compromise egg quality. / Master of Science

Objetivou-se, neste trabalho, detectar o vírus da Influenza aviária, Paramyxovirus tipo 1 (doença de Newcastle), Mycoplasma gallisepticum e Mycoplasma synoviae, respectivamente pelas técnicas de RT-PCR e PCR, em aves domésticas e aves em vida livre próximas às granjas avícolas nas cidades de Mogi das Cruzes e Louveira do Estado de São Paulo. As aves silvestres foram capturadas, anilhadas, submetidas à avaliação de estado geral e à coleta de suabes de orofaringe e cloaca. As aves de subsistência ou fundo de quintal seguiram o mesmo protocolo com a exceção do anilhamento, e tiveram amostras de sangue coletadas para a pesquisa de anticorpos contra o vírus da Doença de Newcastle, Mycoplasma gallisepticum e Mycoplasma synoviae pela técnica de ELISA indireto. Foram considerados os aspectos da biodiversidade entre as espécies silvestres capturadas e a biossegurança nas granjas. As aves silvestres apresentaram resultados negativos nesta pesquisa, no entanto, Mycoplasma gallisepticum e Mycoplasma synoviae foram detectados pela técnica da PCR nas aves de subsistência, assim como apresentaram títulos de anticorpos para os agentes acima citados e para o Paramyxovirus tipo I. Duas granjas não possuíam medidas de biosseguridade adequadas permitindo o contato de animais de vida livre com as aves de fundo de quintal e com as aves de produção, o que pode facilitar a disseminação de patógenos de interesse para a saúde pública e para a avicultura comercial. / The aim of this study is to detect avian influenza virus, Newcastle disease virus (Paramyxovirus I), Mycoplasma gallisepticum and Mycoplasma synoviae in backyard chicken and wildlife birds around commercial poultry farms using RT-PCR and PCR. The birds were captured with mist nets, identified with alluminium leg rings, subjected to the assessment of clinical conditions and samples were collected by oral and cloacal swabs. The same was done with backyard chicken without the identification with leg rings. Blood samples were collected from backyard chicken and tested for antibodies against Mycoplasma gallisepticum, Mycoplasma synoviae and Paramyxovirus I by indirect ELISA test. This study was conducted in Mogi das Cruzes and Louveira, São Paulo state, where the commercial poultry is considered an activity of great importance. The results were negative to wild birds, but we could detect Mycoplasma gallisepticum and Mycoplasma synoviae by PCR and antibodies titles for Mycoplasma gallisepticum, Mycoplasma synoviae and Newcastle disease in backyard chickens.Two farms didn´t have appropriate biosecurity measures, allowing intense contact with free-living birds, backyard chicken and poultry facilitating spread of pathogens with concern to human health and poultry farms.