Equine Grass Sickness Indican Study

Quantification of indican in the serum of Equine Grass Sickness cases and control horses.

Alan Pemberton, University of Edinburgh

The indican study came from a search for putative toxins in Equine Grass Sickness (EGS) serum.  After extensive processing and extraction, a blue-coloured substance was detected in serum from acute EGS cases, but not controls.  This was identified as indigo blue, an artifactual breakdown product of indican (indoxyl sulphate). Therefore, a simple HPLC method was developed to quantify indican in serum from horses.  This was run and the results summarised.  Unfortunately, the original data is lost, only the summary of mean, standard deviation (SD) and the number of animals used in the study (n) remains.  The results indicated a significantly higher concentration of indican in acute EGS samples compared to control horses (or other non-EGS control groups).  Indican is a breakdown product of indole, which is itself produced by bacterial breakdown of tryptophan in the intestine.  Circulating and urine levels of indican are increased where the intestine is obstructed and putrefaction occurs.

Results

Table 1:  Measure of indican in the serum of EGS cases and Control horses.

Disease status

n

Mean (µm)

SD (µm)

Acute GS

14

63.80

52.70

Subacute GS

9

42.60

44.60

Chronic GS

5

8.90

5.80

Colic

7

10.60

6.90

Other controls*

6

10.20

9.40

Healthy horse controls

7

3.60

3.60

* Horses with illness unrelated to the GI tract i.e. lameness