Infection trials in pigs with a human isolate of Brucella (isolate 02/611 ‘marine mammal type’)

Abstract

AIM: To determine if pigs could support infection of a human Brucella isolate (Brucella 02/611) from New Zealand, and to study seroconversion to this isolate using a competitive ELISA.

METHODS: Ten weaner piglets were challenged with 4.8 × 10⁸ cfu of organisms by the oral and ocular routes. Culture was attempted on blood samples taken prior to challenge, and 4, 7, 9, 11, 14, 21 and 28 days post-challenge, and on tissue samples taken at the termination of the trial, 1 month after challenge. Sera were analysed for antibody using an ELISA. For reference comparison, similar trials were conducted in two pigs using an isolate of Brucella suis biovar 1, and two pigs using an isolate of B. suis biovar 3.

RESULTS: Brucella 02/611 organisms were re-isolated from one lymph node each from three pigs; all other samples were negative. Low and transient antibody titres were detected using a competitive ELISA in three pigs, two of which were culture-negative. Organisms of B. suis reference strains were re-isolated from multiple samples from each of the four animals.

CONCLUSION: Brucella 02/611 does not seem to replicate readily in pigs. It is unlikely that pigs were the original maintenance hosts for Brucella 02/611.

KEY WORDs:

• Brucella
• brucellosis
• marine Brucella
• infection trial
• New Zealand
• pig

Acknowledgements

We acknowledge the assistance of John Muschialli and Don Carlson in husbandry and handling of the pigs. Wendy McDonald, Rob Moore and Kim Halpin provided valuable comments on the manuscript. The study was funded by MAF New Zealand.