RESUMEN
The effects of thermal manipulation (TM) at 38.5°C and 40°C for 6 h at embryonic day (ED) 16, 9 h at ED 17, and 12 h at ED 18 on body weight (BW) and cloacal body temperature (Tb) during the first wk and later at post-hatch d 10, 14, 21, 28, and 42 were evaluated. Furthermore, chicks' ability to cope with a thermal challenge (TC; 41°C for 6 h) at post-hatch d 14 and 42 was also evaluated. A chick's response to TC was measured by determining the cloacal body temperature; the plasma thyroid hormones (thyroxin (T4) and triiodothyronine (T3)); the packed cell volume (PCV); the heterophil (H), lymphocyte (L), monocyte, basophil, and eosinophil percentages; and the heterophil-to-lymphocyte ratios (H/L). Thermal manipulation did not affect the hatchability. However, the body weight of TM chicken was higher compared with controls at marketing age (post-hatch d 42). At post-hatch d 14 and 42, no significant changes in Tb were observed among the different treatment groups. However, during TC at d 14 and 42, the Tb of TM chicks was lower compared with the controls. During TC, a significant increase in plasma T4 and a significant decrease in plasma T3 of TM chicks compared with controls were reported. Furthermore, during TC, a significant increase in the PCV and heterophil, monocyte, and H/L ratios, and a reduction in the lymphocyte percentages also were observed in TM chicks compared with the controls. Results of this study showed that chicks subjected to heat manipulation during late embryogenesis respond better to heat stress later in the growth and development period.
Asunto(s)
Regulación de la Temperatura Corporal , Pollos/fisiología , Temperatura , Animales , Peso Corporal , Embrión de Pollo , Pollos/crecimiento & desarrollo , Desarrollo Embrionario , Pruebas Hematológicas/veterinaria , Recuento de Leucocitos/veterinaria , Distribución Aleatoria , Hormonas Tiroideas/metabolismo , Factores de TiempoRESUMEN
Infectious bursal disease virus is a contagious, immunosuppressive disease of young chickens that is controlled by vaccination. Cross-protection occurs between different strains of the virus as a result of shared neutralizing epitopes. However, interactions between two antigenically similar strains (a mild and a pathogenic) coinfecting the same host have not been investigated. Groups of specific-pathogen-free chickens were inoculated with a mild strain followed by a pathogenic strain at 0, 16, 24, or 48 hr postinoculation (PI) with a mild strain. Virus persistence and the predominant strain of the virus were determined by reverse transcriptase-polymerase chain reaction and restriction fragment length polymorphism analysis, respectively, in bursas at 2, 4, 8, 14, and 21 days PI with the pathogenic strain. Severity of infection was assessed by the bursa/body weight ratios and histopathologic lesion scores. The mild virus interfered with replication of the pathogenic virus. The greatest interference was observed when the pathogenic strain was inoculated 24 hr PI with the mild strain. The interference phenomenon observed might be due to competition for host receptor sites or production of cytokine(s). This interference phenomenon could have practical implications for vaccine usage and protection.
Asunto(s)
Infecciones por Birnaviridae/veterinaria , Pollos , Virus de la Enfermedad Infecciosa de la Bolsa/genética , Enfermedades de las Aves de Corral/fisiopatología , Enfermedades de las Aves de Corral/virología , Interferencia Viral , Animales , Infecciones por Birnaviridae/fisiopatología , Bolsa de Fabricio/virología , Ensayo de Inmunoadsorción Enzimática/veterinaria , Virus de la Enfermedad Infecciosa de la Bolsa/patogenicidad , Polimorfismo de Longitud del Fragmento de Restricción , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/veterinaria , Especificidad de la Especie , Organismos Libres de Patógenos EspecíficosRESUMEN
Fertile eggs were obtained from three different broiler breeder flocks with different levels of virus neutralizing antibodies to infectious bursal disease virus. Egg yolk from these flocks was tested for antibody titers by the virus neutralization test. Flock I eggs had no antibodies, flock II had medium level antibodies (1:200-1600; geometric mean = 1:975), and flock III had a high level of antibodies (1:1600-6400; geometric mean = 1:3365). Chicks from the above flocks were challenged each with 10(2) 50% embryo infective dose of the IN serotype 1 variant virus at 1, 2, and 4 wk of age and examined at 5 and 11 days postchallenge. The average organ/body weight ratios were calculated and statistically analyzed. Chicks with no maternal antibodies were not protected at any age. Chicks with medium levels of maternal antibodies were protected when challenged at 1 and 2 wk of age. Chicks with high levels of maternally derived antibodies were protected when challenged at all the ages tested. The above results were statistically significant (P < 0.05).
Asunto(s)
Infecciones por Birnaviridae/veterinaria , Pollos , Virus de la Enfermedad Infecciosa de la Bolsa/inmunología , Enfermedades de las Aves de Corral/inmunología , Enfermedades de las Aves de Corral/prevención & control , Factores de Edad , Animales , Anticuerpos Antivirales/metabolismo , Infecciones por Birnaviridae/inmunología , Infecciones por Birnaviridae/prevención & control , Embrión de Pollo , Femenino , Inmunidad Materno-Adquirida , Virus de la Enfermedad Infecciosa de la Bolsa/clasificación , Pruebas de NeutralizaciónRESUMEN
An investigation was conducted in specific-pathogen-free chickens on the pathogenicity of bursa-derived and tissue culture-attenuated classic (STC) and variant (IN) serotype 1 strains of infectious bursal disease virus. The IN bursa-derived virus caused bursal inflammation, necrosis, and atrophy earlier than the bursa-derived STC virus. Both viruses lost their pathogenicity after four passages in BGM-70 cells. A statistically significant level (P < 0.05) of protection was observed in SPF chickens vaccinated with the attenuated IN virus used as a live or inactivated vaccine followed by homologous (IN) and heterologous (STC) challenge with bursa-derived viruses.