District Veterinary Officer Case Studies
Wet Spring, feet, Orf and … Streptococcus uberis??
Author: Ian Holmes (District Veterinary Officer – Benalla) ASBO; DEDJTR
The long, wet spring this year has caused problems for sheep farmers in Northern Victoria. Plentiful rain has resulted in excellent pasture growth and wet soggy pastures. The combination of a high nitrogen diet from abundant pasture and chronic wet feet typically leads to feet problems in sheep with the classic example being ovine interdigital dermatitis. The persistent moisture softens the interdigital skin allowing the commensal bacterium Fusobacterium necrophorum to penetrate. It is a normal inhabitant of the alimentary tract and faeces of animals and is therefore always present on grazed pastures. As an opportunistic pathogen, this organism causes many necrotic infections including foot abscesses in sheep (and cattle). However, many other organisms can invade the skin that has been compromised by the prolonged wet environment and high nitrogen diet.
In August a farmer from the Nagambie area of central Victoria reported 900 Merino lame weaners with extensive growths at the coronets and lower limbs. A number of sheep also presented with erosions of the lip commissures. Samples submitted to AAHL excluded foot-and- mouth disease and vesicular stomatitis and confirmed the causal organism to be the scabby mouth (orf) parapox virus. Some of the lesions also fitted the description of Strawberry Footrot, a condition typically associated with Dermatophilosis congolensis, that is sometimes seen in combination with the parapox virus. In this case, laboratory testing identified the bacteria associated with the Orf to be Streptococcus uberis. This was an unexpected finding as S. uberis is typically seen in bovine and (dairy) ovine mastitis.
A second case with lesions fitting the description of Strawberry Footrot was reported in October. The local veterinarian was called to a property in the Goorambat area where the farmer had reported lameness in a mob of 400 Merino wethers. On inspection the sheep were found to be severely affected with extensive growths on the back of the feet, typical of the Orf lameness syndrome (see photo below); some had foot abscesses. There were no oral lesions seen in this case. Samples submitted to AAHL excluded foot-and- mouth disease and vesicular stomatitis and confirmed the causal organism to be Orf. In this case no other organisms were detected.
Options for managing the condition are limited and include reducing the overall nitrogen content of the diet by adding grain or hay, attempting to keep the animals feet as dry as possible and the use of oral broad spectrum minerals, such as copper
For more information on scabby mouth (orf), please see the Agriculture Victoria website.
Photos courtesy of Dr Bec Hallett, Benalla VC