Risk factors for new infection with Leptospira in meat workers in New Zealand.

OBJECTIVE

To evaluate risk factors for new infection with Leptospira interrogans sv Pomona and Leptospira borgpetersenii sv Hardjo in meat workers.

METHODS

Sera were collected twice approximately 12 months apart from 592 workers from eight abattoirs slaughtering sheep, cattle or deer and tested by microscopic agglutination for Pomona and Hardjo. Information on potential risk factors were recorded and analysed by multivariable logistic regression.

RESULTS

Forty-nine (8.3%) participants, either seroconverted or had at least a titre increase by two dilutions against either serovar. While in sheep meat workers, the annual infection risk was 11.3% (95% CI 8.5% to 14.8%), in deer meat workers it was 0% (95% CI 0.0% to 10.9%) and in those processing beef cattle, 1.2% (95% CI 0.2% to 4.6%). Risk factors for new infection in sheep abattoirs were worker position, abattoir and time worked in the meat industry. The new infection risk was highest at the beginning of the slaughter line (stunning and hide removal; relative risk, RR 7.5, 95% CI 2.5 to 22.4), followed by positions on the line involving the removal of high-risk material (bladder, and kidneys; RR 5.2, 95% CI 1.7 to 16.0). Risk was lower in the offal/pet food area (RR 4.1, 95% CI 1.0 to 16.4), and lowest in the boning room or office. Wearing personal protective equipment did not reduce the risk of new infection.

CONCLUSIONS

This study has demonstrated ongoing exposure to leptospires in meat workers and risk factors for challenge. We recommend measures such as improvement of personal protective equipment use, changes in slaughter procedure or vaccination of sheep against Leptospira to reduce the risk.