Assuntos
Doenças dos Animais/epidemiologia , Surtos de Doenças/veterinária , Vigilância de Evento Sentinela/veterinária , Animais , Animais Recém-Nascidos , Camelídeos Americanos , Bovinos , Doenças dos Bovinos/epidemiologia , Doenças dos Bovinos/mortalidade , Galinhas , Feminino , Galliformes , Doenças das Cabras/epidemiologia , Cabras , Rinotraqueíte Infecciosa Bovina/mortalidade , Masculino , Doenças das Aves Domésticas/epidemiologia , Gravidez , Escócia/epidemiologia , Ovinos , Doenças dos Ovinos/epidemiologia , Suínos , Doenças dos Suínos/epidemiologiaRESUMO
Bovine respiratory disease (BRD) remains a major health problem despite extensive use of vaccines during the post-weaning period. Apparent vaccine failure is attributed, in part, to primary vaccination during the period of greatest risk for BRD, providing inadequate time for onset of protective immunity. The current study investigated whether intranasal (IN) vaccination of 3-6â¯week old calves with a modified-live viral (MLV) vaccine induced sufficient immune memory to prevent respiratory disease and accelerate onset of protective immunity 5â¯months later. Vaccine groups included naïve controls, a single IN vaccination at 3-6â¯weeks of age, primary IN vaccination at 6â¯months, and either an IN or subcutaneous (SC) booster vaccination at 6â¯months (nâ¯=â¯10/group). All calves were challenged with BHV-1 four days after vaccination at 6â¯months of age. Primary IN vaccination at 6â¯months did not significantly reduce clinical disease but significantly (Pâ¯<â¯0.01) reduced virus shedding. A single IN vaccination at 3-6â¯weeks of age significantly (Pâ¯<â¯0.05) reduced weight loss but did not reduce fever or virus shedding. Both IN and SC booster vaccinations, significantly (Pâ¯<â¯0.01) reduced clinical disease but virus shedding was significantly (Pâ¯<â¯0.001) reduced only by IN booster vaccination. Reduction in virus shedding was significantly (Pâ¯<â¯0.01) greater following booster versus primary IN vaccination at 6â¯months. All vaccination regimes significantly (Pâ¯<â¯0.01) reduced secondary bacterial pneumonia and altered interferon responses relative to naïve controls. Only IN booster vaccination significantly (Pâ¯<â¯0.05) increased BHV-1 specific IgA in nasal secretions. These results confirm primary MLV IN vaccination at 3 to 6â¯weeks of age, when virus neutralizing maternal antibody was present, induced immune memory with a 5â¯month duration. This immune memory supported rapid onset of protective immunity four days after an IN booster vaccination.
Assuntos
Herpesvirus Bovino 1/imunologia , Vacinas contra Herpesvirus/administração & dosagem , Imunização Secundária/métodos , Memória Imunológica/efeitos dos fármacos , Rinotraqueíte Infecciosa Bovina/prevenção & controle , Pneumonia Bacteriana/prevenção & controle , Administração Intranasal , Animais , Animais Recém-Nascidos , Anticorpos Antivirais/sangue , Bovinos , Colostro/química , Colostro/imunologia , Feminino , Herpesvirus Bovino 1/efeitos dos fármacos , Herpesvirus Bovino 1/patogenicidade , Imunidade nas Mucosas/efeitos dos fármacos , Imunoglobulina A/sangue , Rinotraqueíte Infecciosa Bovina/imunologia , Rinotraqueíte Infecciosa Bovina/mortalidade , Rinotraqueíte Infecciosa Bovina/virologia , Masculino , Pneumonia Bacteriana/imunologia , Pneumonia Bacteriana/microbiologia , Pneumonia Bacteriana/mortalidade , Gravidez , Análise de Sobrevida , Vacinação/métodos , Vacinas Atenuadas , Carga Viral/efeitos dos fármacos , Eliminação de Partículas Virais/efeitos dos fármacos , Redução de Peso/efeitos dos fármacosRESUMO
A variety of mechanisms contribute to the viral-bacterial synergy which results in fatal secondary bacterial respiratory infections. Epidemiological investigations have implicated physical and psychological stressors as factors contributing to the incidence and severity of respiratory infections and psychological stress alters host responses to experimental viral respiratory infections. The effect of stress on secondary bacterial respiratory infections has not, however, been investigated. A natural model of secondary bacterial respiratory infection in naive calves was used to determine if weaning and maternal separation (WMS) significantly altered mortality when compared to calves pre-adapted (PA) to this psychological stressor. Following weaning, calves were challenged with Mannheimia haemolytica four days after a primary bovine herpesvirus-1 (BHV-1) respiratory infection. Mortality doubled in WMS calves when compared to calves pre-adapted to weaning for two weeks prior to the viral respiratory infection. Similar results were observed in two independent experiments and fatal viral-bacterial synergy did not extend beyond the time of viral shedding. Virus shedding did not differ significantly between treatment groups but innate immune responses during viral infection, including IFN-γ secretion, the acute-phase inflammatory response, CD14 expression, and LPS-induced TNFα production, were significantly greater in WMS versus PA calves. These observations demonstrate that weaning and maternal separation at the time of a primary BHV-1 respiratory infection increased innate immune responses that correlated significantly with mortality following a secondary bacterial respiratory infection.