RESUMO
The immunity to infectious bronchitis afforded by spray vaccination of mycoplasma free two days-old broilers with maternal antibodies to infectious bronchitis virus was tested by comparing zootechnical scores, clinical signs, macroscopical and microscopical changes, frequency of infectious bronchitis virus isolation following challenge at one, three and five weeks of age in vaccinated, unvaccinated, challenged and unchallenged birds. This vaccination gave a very good protection to infectious bronchitis for the most part of broiler economical life; growth delays were especially avoided. However, vaccinated and unvaccinated one-week-old birds were not protected enough. No correlation was observed between haemagglutinating antibodies titres and protection. At last this vaccination caused a notable reaction in specific pathogen free control birds of the same age.
Assuntos
Bronquite/veterinária , Infecções por Coronaviridae/veterinária , Doenças das Aves Domésticas/prevenção & controle , Animais , Anticorpos Antivirais/administração & dosagem , Bronquite/imunologia , Bronquite/prevenção & controle , Galinhas , Infecções por Coronaviridae/imunologia , Infecções por Coronaviridae/prevenção & controle , Imunidade Materno-Adquirida , Vírus da Bronquite Infecciosa/imunologia , Doenças das Aves Domésticas/imunologia , VacinaçãoRESUMO
In three successive experiments, the immune functions of pigs persistently infected with the porcine reproductive and respiratory syndrome virus (PRRSV) have been evaluated. Non-specific immune responses were analyzed over a period of 12 weeks post-infection (PI). In addition, the capacity of PRRSV-infected pigs to develop an efficient immune response against pseudorabies virus (PRV) glycoproteins and to resist to a subsequent virulent challenge was investigated. Our results demonstrate that PRRSV produced minor effects on the immune system of pigs. The skin delayed type hypersensitivity (DTH) in response to phytohemagglutinine injection was slightly diminished one week after challenge, but was restored thereafter. However, three weeks after the infection, the total white blood cell count, and the number of CD2+, CD8+ and IgM+ cells were enhanced. The increase in numbers of CD8+ cells persisted for three consecutive weeks. Serum immunoglobulins in infected pigs also increased by week 3 PI and up to 8 weeks PI. These results show that PRRSV may have stimulating effects on the pig immune system during the phase of long-lasting infection. After immunization with PRV glycoproteins, the production of anti-PRV antibodies and skin DTH response against PRV glycoproteins were not affected. On the contrary, following a virulent PRV challenge, PRRSV-infected pigs developed a better secondary antibody response and their resistance to the infection was as effective as in control pigs. Taken together, our data do not support a systemic immunosuppressive effect of PRRSV, during the persistent phase of infection. Other mechanisms may therefore apply to explain the emergence of secondary infections in endemically infected herds.
Assuntos
Anticorpos Antivirais/análise , Síndrome Respiratória e Reprodutiva Suína/imunologia , Vírus da Síndrome Respiratória e Reprodutiva Suína/imunologia , Doenças dos Suínos/imunologia , Suínos/imunologia , Animais , Contagem de Células Sanguíneas/veterinária , Antígenos CD2/imunologia , Relação CD4-CD8 , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , Ensaio de Imunoadsorção Enzimática/veterinária , Hipersensibilidade Tardia/imunologia , Sistema Imunitário , Imunoglobulina M/análise , Vírus da Síndrome Respiratória e Reprodutiva Suína/patogenicidade , Pele/imunologia , Viremia/imunologia , Viremia/veterináriaRESUMO
Post-weaning multisystemic wasting syndrome (PMWS) is a comparatively new disease of swine, and known to occur in France since 1996. A porcine circovirus type 2 (PCV2) is found in the lesions of affected piglets. Six piglets aged 10-13 weeks were obtained from a French PMWS-affected farm. Two showing characteristic signs of PMWS (palor, weakness and emaciation) remained in poor condition and were finally killed 6 and 9 days after their arrival in the experimental unit. Tissue homogenates from these two piglets were used to reproduce mild PMWS in specific pathogen-free (SPF) piglets. This mild PMWS consisted of pyrexia (up to 41.7 degrees C) and growth retardation (up to 30% of weight reduction compared with controls) commencing 1 week after infection and lasting 3 weeks. In seven additional trials, pyrexia, growth retardation and lesions characteristic of PMWS were consistently produced in SPF and conventional piglets. However, only four of 55 inoculated SPF piglets (7.2%) showed severe wasting disease. One died and the others had to be killed 3 to 4 weeks after inoculation. None of the inoculated animals developed antibodies to any common swine viruses or bacteria, but clear evidence of PCV2 seroconversion was obtained. Our results therefore strongly suggest that PCV2 is the primary aetiological agent of PMWS.
Assuntos
Infecções por Circoviridae/veterinária , Circovirus/isolamento & purificação , Modelos Animais de Doenças , Doenças dos Suínos/virologia , Síndrome de Emaciação/veterinária , Animais , Infecções por Circoviridae/patologia , Circovirus/patogenicidade , Circovirus/fisiologia , Febre/veterinária , Febre/virologia , Crescimento/fisiologia , Reprodutibilidade dos Testes , Organismos Livres de Patógenos Específicos , Suínos , Doenças dos Suínos/patologia , Síndrome de Emaciação/etiologia , Síndrome de Emaciação/patologia , DesmameRESUMO
This report describes an ELISA blocking test using a peroxidase-labelled monoclonal antibody which binds to the HN protein of Newcastle disease (NDV). This test allows specific detection of type 1 avian paramyxovirus (PMV1) antibodies but does not detect other avian paramyxovirus (PMV2-9) antibodies recognized by the usual serological NDV tests (HI, Orgenics, and Agritech ELISA tests). Furthermore, swollen head syndrome and influenza antibodies were also not detected. ELISA blocking and HI titers of sera collected from SPF chickens immunized with 18 different PMV1 strains (including pigeon isolates) were the same; the correlation between ELISA blocking and HI titers was highly significant (P less than 0.001). In comparison with ELISA tests available commercially at the present time, the ELISA blocking test can be performed more quickly and is applicable without modification to sera from different species of fowls. For this reason, the test appears to be useful for determining the immunity and sanitary status of fowls. When recombinant or deleted vaccines become available, the test should make it possible to demonstrate with confidence any infection of fowls by wild type PMV1.
Assuntos
Anticorpos Monoclonais/imunologia , Ensaio de Imunoadsorção Enzimática/métodos , Hemaglutininas Virais/imunologia , Vírus da Doença de Newcastle/imunologia , Paramyxoviridae/imunologia , Proteínas do Envelope Viral/imunologia , Animais , Anticorpos Antivirais/imunologia , Galinhas/microbiologia , Patos/microbiologia , Estudos de Avaliação como Assunto , Proteína HN , Testes de Inibição da Hemaglutinação , Doença de Newcastle/diagnóstico , Paramyxoviridae/isolamento & purificação , Peroxidase , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Organismos Livres de Patógenos EspecíficosRESUMO
Avoparcin (10 mg/kg feed), bacitracin (50 mg/kg), flavomycin (5 mg/kg) and virginiamycin (20 mg/kg) were tested for their synergy or antagonism on the protective effect of an adult caecal flora administered to 1-day-old chicks. The chicks were challenged experimentally per os with 10(4) to 10(5)Salmonella typhimurium (a rifampicin-resistant strain) when aged 2 days. Chicks receiving avoparcin continuously in the feed had significantly more Salmonella in their caeca than control birds given feed containing no antibiotics; those receiving flavomycin had similar numbers to the controls whereas the groups fed on a diet supplemented with bacitracin or virginiamycin exhibited the lowest level of Salmonella carriage.
RESUMO
Six isolates originating from acute outbreaks of infectious bursal disease recently reported in broiler and pullet flocks in France were studied with respect to their pathogenicity and their antigenic relatedness to the Faragher 52/70 reference strain. Although the mortality experimentally induced in susceptible chickens by the field strains was sometimes four times higher than that which followed the inoculation of the reference strain (16 to 48% versus 12%), neither mortality nor morbidity were observed in chickens previously vaccinated with a commercial live vaccine and then challenged under the same conditions. Agar gel precipitation tests demonstrated the existence of common antigens in the different strains, and high cross-neutralization indices measured in embryonated specific pathogen free eggs showed them all to belong to serotype I. These data are discussed with reference to previous European and North-American studies on the antigenic status of infectious bursal disease virus.
Assuntos
Galinhas , Surtos de Doenças/veterinária , Vírus da Doença Infecciosa da Bursa/patogenicidade , Infecções por Reoviridae/microbiologia , Doença Aguda , Animais , Antígenos Virais/imunologia , Feminino , França/epidemiologia , Vírus da Doença Infecciosa da Bursa/imunologia , Masculino , Infecções por Reoviridae/epidemiologia , Organismos Livres de Patógenos Específicos , Vacinação/veterináriaRESUMO
Five-week-old SPF chickens were inoculated with a virulent strain of M. gallisepticum and half were exposed to an atmosphere containing 100 ppm ammonia. The inoculation reduced weight gain and induced general and respiratory signs (prostration, tracheal rales, and snoring). Tracheal cilial movement was stopped. The severity and duration of M. gallisepticum infection were exacerbated by exposure to ammonia.
RESUMO
In neonates, one limitation of vaccination is its inhibition by maternal antibodies. We show that piglets vaccinated intramuscularly once at birth with recombinant replication-defective adenoviruses developed comparable neutralizing antibody response against pseudorabies virus, independently of the presence or absence of maternal antibodies, and were partially protected against challenge 16 weeks later.
Assuntos
Adenoviridae/imunologia , Imunidade Materno-Adquirida/imunologia , Pseudorraiva/prevenção & controle , Doenças dos Suínos/prevenção & controle , Vacinas Sintéticas/imunologia , Vacinas Virais/administração & dosagem , Vacinas Virais/imunologia , Adenoviridae/genética , Administração Intranasal , Animais , Animais Recém-Nascidos , Anticorpos Antivirais/sangue , Relação Dose-Resposta Imunológica , Ensaio de Imunoadsorção Enzimática , Herpesvirus Suídeo 1/genética , Injeções Intramusculares , Camundongos , Pseudorraiva/sangue , Pseudorraiva/imunologia , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Suínos , Doenças dos Suínos/sangue , Doenças dos Suínos/imunologia , Vacinas Sintéticas/administração & dosagem , Proteínas do Envelope Viral/genética , Proteínas do Envelope Viral/imunologiaRESUMO
Virological 1 examination of a severe infectious bronchitis (IB)-like field case in laying hens, led to the isolation of a coronavirus antigenically different from Massachusetts, Connecticut and four Dutch IB variant strains. The virulence of the isolate for the fowl, and its dual tropism for the respiratory and genital tracts were demonstrated. In preliminary cross-protection studies Commercial vaccines did not protect against challenge with this isolate. These points and the possible economic significance of the virus are discussed.