Modified live (JMSO strain) Haemophilus parasuis vaccine

A vaccine for protecting pigs against infection by Haemophilus parasuis, comprising a veterinarily acceptable carrier and an immunologically effective amount of live cells of an isolated strain of a serovar derived from a pathogenic parent strain of Haemophilus parasuis, wherein said cells exhibit attenuated pathogenicity in pigs as compared to those of the parent strain and wherein said cells are capable of triggering an immune response that protects the pig against Haemophilus parasuis infection when administered as a live vaccine, wherein the parent strain and the isolated strain are serovar 5 of Haemophilus parasuis, wherein the vaccine provides heterologous protection against at least serovars 4 and 13.

A method of preparing a culture of attenuated cells derived from a pathogenic parent strain of Haemophilus parasuis, comprising modifying cells from said pathogenic parent strain, selecting and clonally propagating one or more modified cells that exhibit attenuated pathogenicity in pigs compared to cells of the parent strain, and selecting and clonally propagating one or more attenuated cells which are capable of triggering an immune response that protects the pig against Haemophilus parasuis infection when administered as a live vaccine.

A method for preparing a vaccine to protect pigs against Haemophilus parasuis infection, comprising modifying cells from a serovar of a pathogenic parent strain, selecting and clonally propagating one or more modified cells that exhibit attenuated pathogenicity in pigs compared to cells of the parent strain, and selecting and clonally propagating one or more attenuated cells which are capable of triggering an immune response that protects the pig against Haemophilus parasuis infection when administered as a live vaccine, and combining an immunologically effective amount of the attenuated cells with a veterinarily acceptable carrier in a form suitable for administration as a live vaccine to the pig.

A vaccine for protecting pigs against infection by Haemophilus parasuis, comprising a veterinarily acceptable carrier and an immunologically effective amount of live cells of an isolated strain of a serovar derived from a pathogenic parent strain of Haemophilus parasuis, wherein said cells exhibit attenuated pathogenicity in pigs as compared to those of the parent strain and wherein said cells are capable of triggering an immune response that protects the pig against Haemophilus parasuis infection when administered as a live vaccine, wherein the isolated strain was derived from the pathogenic parent strain by chemical mutagenesis, wherein the isolated strain is dependent on streptomycin for growth, the parent strain and the isolated strain each having a streptomycin resistance (strA) gene.