Two sheep farms running 2500 sheep in total were affected with lameness. In one of the flocks had approximately 70 of 1000 sheep were affected. These two flocks were run semi-extensively, being kept inside only during the lambing period. The rest of the year ewes and rams grazed on the outskirts of Zaragoza in areas that had been kept uncultivated that year. In recent years, the predominant crop was wheat, but at this time weeds such as Amaranthus spp., Salsola kali and Tribulus terrestriswere abundant.
Tribulus terrestis is associated to hepatotoxicity and a chronic progressive, irreversible, locomotor disorder in sheep (Bourke, 2006, 2012 and Finnie, 2011). Tribulus terrestris is a flowering plant in the family Zygophyllaceae, native to warm temperate and tropical regions of the Old World in southern Europe, southern Asia, throughout Africa, and Australia. The flowers are 4-10 mm wide, with five lemon-yellow petals (Fig.1). A week after each flower blooms, it is followed by a fruit that easily falls apart into four or five single-seeded nutlets. The nutlets or "seeds" are hard and bear two to three sharp spines, 10 mm long and 4-6 mm broad point-to-point (Fig. 2). These spines are sharp enough to puncture bicycle tires and lawn mower tires and to cause painful injury to bare feet (Tribulus terrestris in BoDD - Botanical Dermatology Database).
Our services were required because the flock had 7% lame sheep. After the clinical examination of the affected animals any neurological signs were observed and the condition was localized to the hoof. The interdigital space and coronary band were normal. The hooves were cleaned and pared without finding injuries. The soles were then washed and surfaces layers were removed with a knife revealing punctiform lesions in the sole (Fig.3).
These lesions were caused by the thorns of T. terrestris. Sometimes the whole fruit was firmly fixed under the hoof (Fig.4).
In some of the affected animals had these lesions were infected causing hoof separation. Several bacteria were isolated from these due to secondary contamination of sole injuries.
All affected animals were treated with long acting oxytetracyclines and an antiseptic footbath following trimming of the hoof to remove the infected tissue in the worst affected animals. It was recommended that the sheep were not given access to the pastures with abundant Tribulus terrestris.
After the recovery of the affected animals, no more clinical cases of lameness were observed.
In this case T. terrestris has been associated with lameness due to puncture of the sole and contamination of the underlying tissues. Local treatment and long-acting antibiotics resulted in the recovery of almost all affected animals.
Tribulus terrestris should be considered as a cause of lameness in sheep.