Sheep Post Mortem

Post mortem examination of sheep at a fallen stock collection centre to provide information for flock health interventions

Project number:                    73107

Lead contractor:                   Castle Vet, AHVLA

Start & end date:                   01 June 2012 – 31 December 2012

Actual end date:                    15 March 2013

 

The Problem:

Ewe mortality rates in the UK are 5-7%; figures that have remained unaltered for the past ten years.  Average ewe replacement rates, at 20 per cent, are influenced by longevity and may be compromised by diseases that cause premature death or involuntary culling. Accurate, usually necropsy-based, diagnostic methods for common endemic sheep diseases are well established. Indeed, post mortem examination may be the only reliable method of diagnosis for certain diseases, such as Ovine Pulmonary Adenomatosis (OPA) or to a lesser degree, Johnes disease. Accurate mortality rates for specific diseases are lacking on both a flock and national level, because typically only a minority of sheep carcases are subjected to post mortem examination. If established, such information would enable quantification of the prevalence and cost of each disease and thus inform realistic cost:benefit analyses of interventions aimed at improving flock health.

 

Project Aims:

  • Assessment of the diagnostic quality of fallen stock carcases.
  • Demonstration of the value of post mortem examination of fallen stock to the sheep industry.
  • Establishment of costs for providing accurate necropsy-based diagnosis of common sheep diseases.
  • Production of pilot information on the approximate prevalence of ovine diseases, especially those for which there are limited diagnostic tests in the live animal.

 

Approach:

Ten veterinary pathology sessions were conducted at a fallen stock collection centre, which gathers fallen stock from a large area of northeast England.  Each three hour session involved two experienced veterinarians, who examined a random proportion of all available diagnostic ewe carcases, to establish the cause of death. Limited further laboratory diagnostic testing was commissioned where necessary to confirm diagnosis. Agreed minimum diagnostic criteria were used to keep associated costs low.

 

Results: 

The most frequent diagnosis was mastitis, with liver fluke being the next.  The full results can be seen in the table below.  The pilot project suggested that examination at the centre (gross pathology) was reliable, as around 85% of diagnoses needed no further testing, e.g. histology.

Diagnosis Frequency Diagnostic criteria & Notes
No diagnosis

20

Autolysis

9

Carcase too autolysed for meaningful diagnosis
Mastitis

11

Gross udder appearance only (4/11) +/-   bacteriology: contaminants (6/11); M. haemolytica   cultured (1/11)
Acute fascioliasis

8

Gross pathology only
Pasteurella bronchopneumonia

7

Gross pathology only (2/6) + bacteriology (contaminants 2/7) or histopathology (4/7)
Chronic suppurative pneumonia

6

Gross pathology only (6/6)
Neoplasia

6

Gross pathology only (3/6) or   histopathology (3/6)
OPA

6

Gross pathology + histopathology (6/6)
Johnes

6

Gross pathology + faeces PCR (6/6)
Metritis / dystocia / obstetrical

4

Gross pathology only (4/4)
Abomasitis

2

Gross appearance + negative WEC (2/2)Note: suspected type II telodorsagiosis or recent PGE & anthelmintic treatment
Chronic fascioliasis

2

Gross pathology only (2/2)
PGE

2

Gross pathology + WEC (2/2)
Poor Dentition

2

Gross pathology only (2/2)
Peritonitis

2

Gross pathology only (2/2)
Acidosis

2

Gross pathology + rumen pH <5.5   (2/2)
Salmonella   61:K;1,5,7

2

Gross pathology (scour) + Salmonella cultures (2/2) Note: Not considered an adequate cause of death
Dosing gun injury

2

Gross pathology only
Megaoesophagus

1

Gross pathology only
CLA

1

Caseous mediastinal lymphadenopathy + C.   pseudotuberculosis cultured
Endocarditis

1

Gross pathology only
Acetonaemia / Fatty Liver

1

Gross pathology + ketonuria
Abdominal torsion

1

Gross pathology only
Chronic nephritis

1

Gross pathology + histopathology
Suspect larval paramphistomum

1

Gross pathology only

Total

106

 

Although good bacteriology results proved difficult to obtain, this study has shown that it is possible to diagnose the cause of death from fallen stock.  It was proposed that the systematic necropsy of fallen stock would improve data on disease incidence, and with appropriate communication back to farmers would encourage good health planning.

 

Planned activity:

Abstracts were submitted to International Sheep Veterinary Congress and British Society of Animal Science conference.  A short communication was published in the Veterinary Record in April 2013.  The results will be included in a health and welfare paper submitted to the EBLEX board, plus a report of ewe mortality in England.