Virulence of Avian Capsular Serogroup B Pasteurella multocida for Turkey Poults

SUMMARY. Two strains of capsular serogroup B Pasteurella multocida isolated from avian hosts (swan and turkey) were evaluated for virulence based on lethality for turkey poults. Groups of poults were exposed intramuscularly to various concentrations of organisms of each strain. Both strains were virulent. The strain isolated from a turkey was highly virulent: all exposed poults died in less than 24 hours, including those exposed to only 79 organisms. This highly virulent strain was neither highly invasive nor highly infective: intrapharyngeal exposure with 7.9 x 106 organisms resulted in death of only one of five poults, and attempts to isolate the organism from pharyngeal mucosae and livers of surviving poults were unsuccessful. The high degree of virulence of a B capsular group strain isolated from a turkey indicates a diseaseproducing potential for members of this uncommon serogroup of P. multocida. RESUMEN. Virulencia del serogrupo B encapsulado aviar de Pasteurella multocida en pavitos. Se estudi6 la virulencia de dos cepas del serogrupo B encapsulado de Pasteurella multocida aisladas de cisne y pavo, basandose en el grado de letalidad en pavitos con varias concentraciones de cada una de las cepas virulentas. La cepa aislada de pavo fue muy virulenta: todos los