Blindness in Lambs After Housing

Some farmers may choose to house their ‘tail end’ lambs for finishing, either to preserve limited grass stocks for ewes, to manage potential fasciolosis risk or to achieve a quicker and more efficient finish before lambing starts in 2021.  One condition to be aware of in these circumstances is a ‘post housing encephalopathy’ which is probably as a result of indirect salt poisoning or water deprivation.

Our Aberdeen centre have diagnosed a case this autumn and we saw a series of cases on two farms this time last year.  The history is quite specific; usually an onset of clinical signs one to two days after housing, sometimes slightly longer, possibly because the lambs were unfamiliar with the water source.  It has also been recorded following a known interruption of water supply.  The clinical signs are blindness in otherwise multiple apparently healthy lambs.  Occasionally more severe neurological signs such as head pressing or teeth grinding and sudden deaths can be seen.

Differential diagnoses include CCN, sulphur toxicity, closantel toxicity and lead poisoning.  The clinical history and a lack of response to vitamin B1 therapy is quite characteristic in these cases.  It has been suggested that high blood sodium levels in clinically affected sheep may provide supportive diagnostic information.  At post mortem examination of aqueous and vitreous humour, plus brain, eye and visceral histopathology can help confirm a diagnosis.

More information can be found here.

Posted by Veterinary Services on 18/12/2020