JOHNE'S DISEASE

COLLECTION AND SUBMISSION OF POST MORTEM SAMPLES

ABATTOIR

As most collection of samples will be at an abattoir, familiarity with the operation of the abattoir and a good relationship with management is essential. Collection of inappropriate samples, or samples from the wrong animals are common mistakes made at an abattoir. Failure to submit the correct specimens may prevent a negative follow up to progress the status of a herd! There is a "Duty of Care" to submit correct specimens.

As well as a blood sample and a faecal sample you should collect the last 60 cm of the ileum, the caecum, the first 30cm of the proximal colon: their mesenteric attachments (mesenteric lymph nodes) should be detached as one, from the rest of the gut. The ends of the gut should be tied before cutting to minimise spillage. The required gut should then be placed in a sealable container clearly labelled and transported back to the laboratory for sampling.

The sample is laid out so as to clearly identify landmarks. The ileum, caecum and proximal colon can be identified visually, the lymph nodes are visible on animals with low amounts of mesenteric fat and the ileocaecal valve is palpable at the junction of the ileum and the caecum.

A minimum of seven samples must be taken (see Sites for Collection of Tissue Samples for NJDMAP)

1. one (10cm X 5cm) from the proximal colon adjacent to the valve
2. the entire ileocaecal valve itself
3. one (10cm X 5cm) from the distal ileum adjacent to the ileocaecal valve
4. one (10cm X 5cm) from the ileum 20 cm proximal to the ileocaecal valve
5. all the ileocaecal lymph nodes
6. mesenteric lymph nodes, about 5cm proximal to the ileocaecal valve
7. one (10cm X 5cm) sample of caecum adjacent to the ileocaecal

The gut samples for culture should be placed in individual sterile pots, labelled with animal ID and site of origin. A small section from each of the 5 gut samples (a 2cm X 2cm) section should be separated and placed in 10% formol saline for histopathology. The samples for histopathology can be pooled in formalin in the one container per animal, clearly labelled with the animal's permanent identification.

The lymph node samples should be sectioned, with a slice 0.5cm in thickness into 10% formal saline for histopathology. The other portion should be put into individually labelled sterile pots (ie all the ileocaecal lymph nodes in one pot and the mesenteric lymph nodes in another) for culture.

The entire gut, including caecum should be opened and washed and examined for any pathological changes (hyperaemia, thickening etc). These additional areas should be dissected, with a small sample taken for histopathology and the remainder in sterile labelled bottle for culture.

STORAGE OF SAMPLES

The samples for culture should be dispatched to the diagnostic laboratory so as to arrive at the approved laboratory within 48hrs. The samples should be chilled not frozen and sent in a sealable cool box with an ice brick.