The wet weather and flooding of late summer-autumn 2011 and again in late summer-autumn 2012 resulted in a number of reports of foot abscess in the western parts of the North West LHPA. This report documents a typical case.
The affected enterprise was a Walgett district Merino ewe flock, joined to both Merino and Border Leicester rams. Total sheep numbers were 4,500 head. At the time of the property visit, the property was still isolated by flooding and could only be accessed by quad bike (Figure 1).
In early March, the owner noticed approximately 30 lame ewes from a mob of 1,500. The Merino ewes had been grazing on tall, lush, natural pastures. The property had been flooded since early February and most paddocks had been consistently moist since early December rains. After discussing the case with a LHPA veterinarian, the ewe mob was mustered and affected ewes removed for inspection by a LHPA Ranger. Differential diagnoses included virulent footrot, strawberry footrot and foot abscess. As well as visual inspection, the Ranger took photographs.
On examining the affected ewes, four-fifths were found to be lame. The hind limbs were most commonly affected, and most ewes had more than one foot affected.
Affected feet had swelling above the coronet. Purulent discharging sinuses were often present on the coronet or in the interdigital space (Figures 2, 3 and 4). The interdigital space was commonly inflamed with hair loss from friction (Figure 5). A large proportion of the ewes had overgrown hooves, which may have predisposed the flock to the condition (Allen 2010).
Based on the history and clinical observation, a likely diagnosis of foot abscess was made. Virulent footrot was excluded on the basis of minimal inflammation of the skin of the interdigital space and no under-running of the horn. A LHPA veterinarian examined photographs of the feet and confirmed the diagnosis.
The ewes were treated parenterally with long-acting oxytetracycline. Other recommendations included moving the ewe mob to a drier paddock and holding clinical cases on boards in the shearing shed for three days after antibiotic administration.
A total of 46 ewes were found to have foot abscess and were treated. In the days following the property visit, further inspection of a mob of first cross ewe weaners found another 22 with abscesses. These were treated as per the ewes.
Two weeks after the initial treatment 32 of the 46 ewes, and 16 of the 22 weaners had fully recovered after a single injection. All remaining lambs, and all but four ewes, recovered fully with a second injection administered four days after the first.