This report outlines a case of illness and mortalities in ten month old cross bred lambs with depression, lameness and joint swellings post shearing. Laboratory findings included tubulointerstitial nephritis with crystals and suppuratives meningitis, and Erysipelothrix rhusiopathiae was isolated from the joint of one lamb. There are four classified manifestations of E. rhusiopathiae infection in sheep; valvular endocarditis, cutaneous infections, septicaemia and polyarthritis (Radostits et al). In the central west of NSW Erysipelas arthritis is the most common form diagnosed. While E. rhusiopathiae culture supported the clinical findings of lameness and joint swellings, culture of kidney and brain tissues was not conducted to confirm whether E. rhusiopathiae was also responsible for the nephritis and meningitis found. It remains possible that another agent was involved and contributing to the illness and mortalities in these sheep.
In June 2014 a producer from Lake Cargelligo in the south western Central West Local Land Services region reported illness with mortalities in a mob of 350 ten month old Merino x White Suffolk lambs. The lambs were originally purchased from the northern tablelands area of NSW in March and had been given a multivalent clostridial and CLA vaccine combined with moxidectin (moxidectin 2.5g/L plus clostridial and C. pseudotuberculosis antigens, 1ml per 12.5 kg SC, Cydectin Weanerguard® Virbac) at arrival on farm. Five weeks previously they had been given a drench combining abamectin and praziquantel, (abamectin 0.8g/L and praziquantel 15g/L, 1mL/kg bodyweight orally, Firstmectin®, Virbac) and then turned onto a fresh oat crop. The lambs had been shorn 14 days previously. A small number were noticed unwell three days after this with depression, lameness with joint swelling and scouring. They died despite treatment with a short acting dose oxytetracycline, (20mg/kg IM; Engemycin 100, Intervet/MSD). At the time the report was made there had been 10 deaths, 3 animals were unwell in the yards and a further five affected animals had been noticed in the paddock.
The three animals in the yards were examined. All were depressed, reluctant to move and had significant joint swellings, particularly of the carpus and hock. One animal had a mild green scour. Rectal temperatures were 39.2, 39.6 and 39.8 degrees Celsius.
The most depressed lamb was euthanased for post mortem. There was a 100mm x 15mm healing shearing wound on the neck covered by a thick, dry scab. The right hock was significantly swollen and painful with the left carpus and right hock also mildly swollen. Both kidneys were enlarged approximately ten percent and slightly soft compared to normal, and the entire surface was covered with multifocal to coalescing tan coloured foci (Figure 1). The kidney bulged on cut surface and tan striations were present in the cortex and medulla (Figure 2). Joint fluid in the stifle was bright yellow and clear - no other joint changes were noted (Figure 3). Excess cerebrospinal fluid was noticed beneath the meninges.
Samples were collected and submitted to the Elizabeth Macarthur Agricultural Institute laboratory in Menangle, NSW for examination. These included blood and urine, fixed and fresh tissues, faeces and both carpal joints whole and intact.
The chlamydia CFT titres from the sheep examined were all <8 and the nematode egg count on bulked faeces was 120 epg.
The USG on the sheep necropsied was 1.020, and urinalysis was unremarkable. Histopathology showed tubulointerstitial nephritis with crystals present within dilated tubules, and suppurative meningitis. Joint fluid culture grew E. rhusiopathiae and sensitivity testing determined resistance to sulphurazole, trimethoprim and novobiocin and sensitivity to tetracycline, erythromycin and penicillin.
E. rhusiopathiae is a ubiquitous organism able to persist for a long time in the environment. It is a significant pathogen of the pig industry causing Swine Erysipelas. The disease in pigs is characterised by sudden onset of fever, anorexia and typical diamond-shaped skin lesions in the acute form, and arthritis and endocarditis in the chronic form (Radostits et al). Sites recommended for collection of samples for bacteriological confirmation in pigs are joints, heart valve masses, spleen and kidney (Radostits et al).
E. rhusiopathiae can cause heavy mortalities in lambs from septicaemia (Bennetts 1952) and has been isolated from the heart valves of lambs (Seddon 1965). It has also been implicated in a report of arthritis and meningitis in association with septicaemia and diarrhoea in lambs (Nicolas et al 1980)
In this case all three lambs examined had clinical evidence of Erysipelothrix arthritis (confirmed in one animal). The necropsied lamb also suffered from nephritis and meningitis. While pigs infected with E. rhusiopathiae can develop embolic nephritis (Newman et al 2007), the kidney pathology in this case (presence of crystals in the tubules) was not consistent with this. Without bacterial culture of the kidney and brain tissues the suggestion that E. rhusiopathiae also caused the nephritis and meningitis remains speculation only.