RESUMEN
The antigenic relationships between 17 Australian infectious bronchitis viruses, including six vaccine viruses, were studied by a neutralisation test using a plaque reduction method in chick embryo kidney cell monolayers. The 17 viruses formed nine distinct subtypes. Antiserum to each subtype had a high titre to viruses of the same subtype and a lower titre to viruses of different subtypes. The heterologous titres of sera varied widely.
Asunto(s)
Coronaviridae/inmunología , Virus de la Bronquitis Infecciosa/inmunología , Pruebas de Neutralización , Antígenos Virales/análisis , Australia , Células Cultivadas , Virus de la Bronquitis Infecciosa/crecimiento & desarrolloRESUMEN
Twenty-three chickens, aged 9 weeks, were housed in contact with a similar group of chickens which were infected with M. gallisepticum. The onset and development of the serum agglutinin responses which were detected by 3 commercial antigens using rapid serum agglutination tests up to 20 weeks of age, differed greatly both between the infected and in-contact groups and, within the latter group, between the antigens. Few reactions, which were weak and transient, were detected in 2 similar groups of chickens, neither infected with M. gallisepticum but 1 vaccinated at 12 and 17 weeks of age with killed Pasteurella multocida oil adjuvant vaccine.
Asunto(s)
Antígenos Bacterianos , Pollos , Infecciones por Mycoplasma/veterinaria , Mycoplasma/inmunología , Enfermedades de las Aves de Corral/diagnóstico , Pruebas de Aglutinación , Animales , Infecciones por Mycoplasma/diagnósticoRESUMEN
Cutaneous myiasis in Australian sheep became an increasing problem in the early years of the 20th century after the import of the wrinkly Vermont Merinos and the introduction of Lucillia cuprina. WE Abbott, a successful pastoralist in New South Wales at that time, wrote a little-known and unusual description of early methods of control: a parody based on an episode in Through the Looking Glass by Lewis Carroll. The plight of struck sheep and the lives and times of Abbott, several other pastoralists and the entomologists of the New South Wales Department of Agriculture are illuminated as the Walrus and the Carpenter walk again across the hills and pastures of New South Wales.
Asunto(s)
Miasis/veterinaria , Enfermedades de las Ovejas/historia , Animales , Australia , Dípteros , Entomología/historia , Historia del Siglo XX , Miasis/historia , OvinosRESUMEN
The cross-immunity of vaccinated chickens after challenge with some Australian infectious bronchitis viruses was assessed by humoral antibody responses and by ciliary activity in tracheal rings of vaccinated chickens following challenge. Four viruses were used for vaccination: Vac 3, Vac 4, both current infectious bronchitis vaccine viruses, and Q1/76 and N2/62. IBV N1/62 (synonym T0 and infectious bronchitis virus N9/74 (synonym Appin) were used to challenge the vaccinated chickens. Results showed a lack of correlation between humoral antibody levels and protection. Cross-immunity was found after vaccination with each subtype, but was lower for Vac 3 and Vac 4 than for Q1/76 and N2/62.
Asunto(s)
Pollos , Infecciones por Coronaviridae/veterinaria , Coronaviridae/inmunología , Virus de la Bronquitis Infecciosa/inmunología , Enfermedades de las Aves de Corral/prevención & control , Vacunas Virales , Animales , Anticuerpos Antivirales/biosíntesis , Cilios/fisiología , Infecciones por Coronaviridae/prevención & control , Reacciones Cruzadas , Pruebas de Inhibición de Hemaglutinación , Organismos Libres de Patógenos Específicos , Tráquea/fisiopatología , Vacunación/veterinariaRESUMEN
Very virulent Marek's disease viruses (vvMDV), defined as isolates against which the herpesvirus of turkey (HVT) vaccine provide poor protection, have been isolated from poultry flocks in both the United States and Europe. Twenty-one samples from vaccinated Australian flocks, experiencing problems with excessive Marek's disease (MD), were tested for the presence of transmissible MD viruses (MDV). Of the 16 samples which contained a transmissible agent, 14 were pathogenic in chickens, based on the development of MD lesions or depression of the bursa/body weight ratio. Of the pathogenic isolates which have been successfully typed 10 were serotype 1, and one was serotype 2 MDV. Pathogenicity of isolates varied. Several isolates caused tumours in 20-30% of both vaccinated and unvaccinated chickens. Two isolates, MPF6 and MPF23, caused tumours in more than 50% of chickens. When MPF6 and MPF23 were tested in vaccine trials bivalent vaccine gave no better protection against development of MD lesions than a monovalent vaccine. Isolate MPF23 was so pathogenic that lesions were produced in all chickens, regardless of the vaccine protocol used. Therefore vvMDV have been isolated in Australia, and unlike the vaccines tested overseas, bivalent Australian vaccines do not appear to provide greater protection against these vvMDV.