An apparently rising incidence of lesions described as “Nephritis” in lambs being inspected at two major abattoirs in South Australia led to a study attempting to define the syndrome, it’s costs to production (if any) and possible mitigations.
A limited study has been designed in three parts to provide information, and hopefully conclusions that will be helpful to producers and Industry.
This paper describes progress to date, and the plan ahead.
The South Australian Enhanced Abattoir Surveillance program (EAS) has been in operation for 10 years and inspectors are employed to examine lines of sheep, both mutton and lambs at two major export abattoirs in South Australia. Requirements are that there must be at least 100 sheep per line, and the sheep bodies and viscera are examined by trained staff for 19 different conditions, and an estimate of incidence in the line is determined and recorded. These statistics are reported to PIRSA and if incidence exceeds a determined threshold a letter is sent to producers with the report and a factsheet on the subject. (see examples in Appendix)
Nephritis is a condition that inspectors report and the Murray Mallee area appears to have a higher incidence of these reports than other areas. This area is semi-arid cropping and grazing country with average rainfalls between 250 to 400mm per year and there appears to be a rising incidence of these reports between 2015 to 2017. A brief study was designed to attempt to identify a case definition, causality and risk factors.
The first questions to answer were:
What are inspectors seeing that is reported as “Nephritis”?
Is there a consistent pathology associated with these kidneys?
From the pathology, is there a plausible aetiology for the condition?
The study has 3 parts, and only involves lines of lambs.
Part one involves identifying properties with persistently high reports of nephritis in lambs, gather some samples from kidneys identified as nephrotic, and determine the pathological lesions. This may assist in identifying risk factors or aetiology.
Part two is interviewing producers with a standardised checklist to identify common factors & management processes and to look at the data to identify seasonal, spatial and other trends. Non affected producers in the same area will also be interviewed as controls. Attempt to identify production changes or losses, if any.
Part three is collation and conclusions, and attempting to answer the questions:
Is this syndrome causing production loss in affected sheep, or could it in future (older) sheep?
Is there an identifiable cause that could be addressed?
What mitigations might be possible to lower the incidence?
This will be published as a final paper to producers and the funding body for the EAS Program, the SA Sheep Advisory Group.
Initial Case Study SA252849
The project started with a single Mallee producer who received reports of “Nephritis” lesions in lambs consigned to Thomas Foods International (TFI) at Murray Bridge.
The producer contacted PIRSA requesting assistance in determining the cause of these reports, and advice on how to reduce the incidence.
The first step was to see what Inspectors were calling “nephritis” and to determine whether there was a consistent pathology.
Lambs were sampled on 2 occasions by arrangement with TFI with results reported below.
Case definition – Inspectors: “any kidney that is misshapen, or has a white mark or spot on the surface. Any lesion seen on cut surface of the kidney” or as described in the Factsheet:
“Nephritis is the term used to describe damaged kidneys. The damage seen at the abattoir may have been caused:
Some time ago - kidneys are usually shrunken, irregular and scarred; or
Recently - kidneys are usually swollen and may be discoloured or spotty.
On collection of 42 affected kidneys on 10/10/2016, kidneys were grouped into classes (subjectively) of mild (1 or 2 very small white spots), medium (more than 2 white spots, some 3-4 mm in diameter) or severe lesions (large spots > 5mm, misshapen kidneys or visible cysts) and results are described below.
|% of total sampled kidneys||26||40||34|
|% of total sheep slaughtered||7||11||9||27|
Further samples will be obtained in coming months from producers identified previously with high incidence of “nephritis” lesions, and a standardised questionnaire is being developed.
Case definition – pathologists (quoted from pathology report)
“Diagnosis: pyelonephritis & tubulointerstitial nephritis, multifocal, chronic, mild to marked, with interstitial fibrosis, lymphofollicular hyperplasia & focal abscessation.
Comments: (partial extract) The chronic inflammatory lesions identified within the submitted kidney samples are essentially similar and suggest a spectrum from mild to moderately severe lesions, although, subjectively, there is not much difference between the kidneys grossly categorised as moderate vs.severe. These lesions are compatible with chronic pyelonephritis and multifocal areas of cortical tubulointerstitial nephritis. This likely reflects an ascending bacterial urinary tract infection with extension of the offending agent from the pelvis into the renal parenchyma. The consistent involvement of the renal pelvis (especially in the mild category, where there are few cortical inflammatory foci) suggests that haematogenous infection of the kidneys (i.e. embolic nephritis) is a less likely route of infection. In one of the 'severe' kidneys, there is formation of a small abscess within the inner cortex.
No specific inciting cause can be identified microscopically, i.e. no bacteria, fungi, parasites, etc. Leptospiral organisms were not detected in a fresh kidney sample tested by PCR; however, this does not fully exclude this as a potential possible agent.
The study has been designed as a low cost, low input study with limited resources attempting to provide practical answers to producers who have identified an issue of concern.
Farming is an increasingly complex and stressful operation, particularly in mixed enterprises and where producers are seeking to maximise growth rates and production, while minimising costs.
The PIRSA EAS program has been very well received by SA producers and continues to be 80% funded by SA Industry, and is seen as delivering helpful, timely and good quality advice to producers, agents, and others engaged in Industry.
The study, when it concludes, will hopefully be able to answer questions that concern producers, and if any production defects can be identified, will hopefully assist with recommendations.
|Elise Matthews||(08) 8207 7837||elise.matthews|
Nephritis is the term used to describe damaged kidneys. The damage seen at the abattoir may have been caused:
|On Farm||At the Abattoir|
Reduced growth rate/weight loss – in cases of long term kidney damage. Can be significant.
Deaths – may be sudden or after weeks to months of doing poorly (depending on cause).
Kidney condemnations – affected kidneys are condemned (this is an industry cost as does not affect carcase weight for producers).
Carcass condemnations – rare, associated with whole of carcass effects of kidney failure (e.g. fluid accumulation in the tissue).
There are many causes of nephritis however the most common include:
Signs of nephritis will only be seen if 75% or more of the kidneys are damaged, kidneys have a large reserve capacity. If damage is significant decreased production, growth and/or death may be seen. If damage is mild then sheep may show no signs of illness or adverse production affects.
Signs of nephritis are highly variable as there are many possible causes and both sudden and longer term problems, due to resultant kidney failure, are seen. Signs in a flock indicative of chronic kidney damage can include:
Treatment will vary depending on the cause of nephritis and whether the problem is sudden or has developed over time. Sheep should immediately be moved (slowly) from known toxic plants.
FOR FURTHER INFORMATION: contact the Enhanced Abattoir Surveillance Program manager Dr Elise Matthews, your local veterinarian, livestock consultant or PIRSA Animal Health Officer.
FOR ANY SIGNS OF UNUSUAL OR SERIOUS DISEASE, PLEASE CALL THE ANIMAL DISEASE HOTLINE: 1800 675 888
Photos of kidneys sampled on 10/10/2016
“Severe nephritis “
Grossly misshapen, visible cysts or larger white spots on surface extending into cortex
Medium 1 or 2 white spots on surface, occasion calcified area in medulla
Mild hardly any visible lesions on surface, maybe 1 small white spot