C Turni1, R Singh1, P J Blackall1. 1. Queensland Alliance for Agriculture and Food Innovation, Level 2A EcoSciences Precinct, The University of Queensland, Boggo Road, Dutton Park, Queensland 4102, Australia.
Abstract
OBJECTIVE: Determine if there is a link between virulence-associated genes of Haemophilus parasuis and the genotype and serovar of isolates. METHODS: Isolates of H. parasuis from 38 farms across six Australian states, representing all serovars present in Australia, were assessed for the presence of virulence-associated genes (vtaA, hhdBA, fhuA, lsgB and capD). Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR) and multilocus sequence typing (MLST), together with existing knowledge of the serovar of the isolates and the health status of the source pig, were used to examine 75 Australian isolates of H. parasuis. RESULTS: An analysis of the ERIC-PRC patterns revealed six main clusters. One cluster of 25 isolates lacked virulence-associated genes and on the basis of serovar and field data, appeared to be mostly non-pathogenic. Another cluster of five isolates containing most of the virulence-associated genes appeared to be pathogenic based on the field and serovar data. The remaining four clusters were a mix of apparently pathogenic and apparently non-pathogenic isolates. The MLST results revealed a high degree of variation, with 54 sequence types of which 41 had not been previously recognised. CONCLUSION: Not all virulence-associated genes are present in potentially pathogenic strains of H. parasuis. Australian isolates of H. parasuis are both genetically diverse and markedly different from isolates in other countries. These key findings suggest that vaccine development will be challenging.
OBJECTIVE: Determine if there is a link between virulence-associated genes of Haemophilus parasuis and the genotype and serovar of isolates. METHODS: Isolates of H. parasuis from 38 farms across six Australian states, representing all serovars present in Australia, were assessed for the presence of virulence-associated genes (vtaA, hhdBA, fhuA, lsgB and capD). Enterobacterial Repetitive Intergenic Consensus PCR (ERIC-PCR) and multilocus sequence typing (MLST), together with existing knowledge of the serovar of the isolates and the health status of the source pig, were used to examine 75 Australian isolates of H. parasuis. RESULTS: An analysis of the ERIC-PRC patterns revealed six main clusters. One cluster of 25 isolates lacked virulence-associated genes and on the basis of serovar and field data, appeared to be mostly non-pathogenic. Another cluster of five isolates containing most of the virulence-associated genes appeared to be pathogenic based on the field and serovar data. The remaining four clusters were a mix of apparently pathogenic and apparently non-pathogenic isolates. The MLST results revealed a high degree of variation, with 54 sequence types of which 41 had not been previously recognised. CONCLUSION: Not all virulence-associated genes are present in potentially pathogenic strains of H. parasuis. Australian isolates of H. parasuis are both genetically diverse and markedly different from isolates in other countries. These key findings suggest that vaccine development will be challenging.
Authors: Maria Jose Clavijo; Alexander Tucker; Virginia Aragon; Nubia Macedo; Marcelo Gottschalk; Katrin Strutzberg-Minder; Chao Nguyen Van; Lijun Zhang; Geng Zou; Rui Zhou; Thaire Marostica Journal: Vet Res Date: 2021-05-12 Impact factor: 3.683