Subject: The sheep affected were Romney Marsh ewes and lambs. The ewes were of good type, and were used by the owner to breed his flock rams. They were of varying ages and numbered 147, with lambs from three weeks to three months old at foot.
History: The condition had developed within the eight days preceding inspection. Eight days previously the mob had been shorn, and were held 24 hours in the shed. After leaving the shed, they were put into a small paddock carrying little feed except stunted barley grass about four inches high, but with fully developed seed heads, almost ripe. Inspection of this paddock revealed that this grass had been eaten off. The owner advised that the sheep were suffering from a facial condition characterised by swelling and black staining of the face, and that one ewe had died.
Symptoms: On inspection 14 ewes and 7 lambs were found to be showing gross swelling of the lips and face, and a distinct black staining of the hair and wool about the face. Affected sheep were poorer in condition than the remainder of the flock, and all showed varying degrees of muco-sanguineous nasal discharge. Close examination of several bad cases revealed that the swelling was only slightly oedematous. The most obvious feature was the presence of literally thousands of blow-fly larvae in the lesions, and these had removed large pieces of flesh from the lips and face, and in one case there was an almost complete, bilateral under-running by the maggots of the healthy skin over the masseter muscles. Several cases showed direct passage from the face to the nasal cavity, and through the palate to the buccal cavity. Two ewes were seen to be breathing through these sinuses, and not through the nostrils which were blocked by nasal discharge and a seething mass of larvae.
As this was obviously a case of acute strike, and so much tissue damage had resulted, the predisposing cause was completely masked. Consequently, a further examination was made of several ewes showing less marked, but still obvious, swelling and staining, and which had not been struck. This revealed the presence of marked ulcers, all of which were packed tightly with barley grass seeds, on the palate and between the cheeks and gums. In the more advanced cases the seeds had penetrated into the nasal cavity or through the cheeks to the face. It was a mass invasion of seed over large areas. From this it was obvious that the initial lesions were caused by the seed, and that once penetration from mouth to face was complete, conditions became attractive to the primary fly, which was active at the time. This strike was soon followed by the secondary fly in large numbers. and these larvae invaded not only the tracks of the seed, but also the surrounding healthy tissues. An equally heavy infestation of blow-fly larvae had not been seen previously. Post mortem examination of one case revealed that the maggots had removed portion of one turbinate bone, and had invaded both the hard and soft palates.
Treatment: Treatment of the struck sheep was considered impossible in view of the extensive tissue damage, and the owner was advised to destroy them and burn the carcases. This was done, 12 ewes and 5 lambs being destroyed. It was recommended then that each individual sheep be examined, all grass seeds be removed from the mouth lesions and the lesions then swabbed with a five per cent. solution of copper sulphate, to be repeated in three days. When carrying out the treatment, only a further 10 bad cases were found. All cases were treated, raddled, and returned to the flock, which was then depastured in a paddock containing sub clover and rye grass. When yarded three days later the lesions were found to be clean and apparently healing. Treatment was repeated and a further examination three days later revealed that healing was so well in progress that no further treatment was necessary. Cases showing facial lesions were not struck following treatment with the copper sulphate.
Discussion: The extremely rapid penetration of the tissues by the grass seeds, and the extensive tissue damage by the blow-fly larvae are remarkable in this case. The basal cause of the condition was the starvation period in the yards, and the fact that no selective grazing was available to the sheep, which were forced to eat the barley grass. It might be noted that only the older lambs were affected, and secondly that no alveolitis was noted in the flock.