Investigating the potential link between tail length and arthritis in sheep

Summary

Arthritis/polyarthritis caused by bacterial infections is a relatively common condition in lambs and has recently been identified as one of the priority endemic disease of Australian sheep for MLA research investment.

The primary objective of this research project was to investigate if there is an association between tail length and arthritis in lambs. If there is, attention to correct tail length when docking would be a cost-effective method way of reducing the prevalence of arthritis in sheep. The hypothesis was that short docking leads to infected tailing wounds that take longer to heal, with subsequent spread of bacteria through the blood to the joints, resulting in arthritis/polyarthritis.

Arthritic joint samples collected from lamb carcases at an abattoir in South Australia were tested by culture, PCR and immunohistochemistry for the presence of bacteria.

In addition, data from the South Australian Enhanced Abattoir Surveillance Program database were analysed to determine the historical occurrence of arthritis in sheep less than and more than two years of age, including potential correlations with age, region and anonymous property identifier, as well as potential correlations between grass seed infestation and arthritis, and between pneumonia/pleurisy and arthritis.

An association between tail length and bacterial arthritis/polyarthritis in lambs was identified, with shorter tails (one or two coccygeal vertebrae) being a higher risk factor for arthritis/polyarthritis than longer tails (three or more coccygeal vertebrae). Erysipelothrix rhusiopathiae was re-confirmed as the most common cause of bacterial joint infections in Australian lambs. In lambs, E. rhusiopathiae usually causes a fibrinopurulent arthritis and osteomyelitis after docking or castration.