Nutritional osteodystrophy in iguanas

-Nutritionally induced osteodystrophy is probably the commonest disease of iguanas (Iguana iguana), affected animals being dull and lethargic, with a decreased appetite. Activity is usually reduced, often to the point that the hindlimbs barely move and muscles may be atrophied. The animals appear closer to the ground and may present with 'spontaneous' fractures. Tetany (convulsions and rigidity) may also be seen. In females the onset of egg laying may precipitate the appearance of signs, despite the eggs being normally soft-shelled .

Undermineralisation is relatively obvious on radiography and blood calcium levels will be below the normal 2.3 mmol/l .

Treatment of acute hypocalcaemia involves rapid correction of the blood levels using 1% calcium gluconate (0.5ml of 20% in 9.5ml water) at a rate of 1-2ml per 100g body weight - 100-200mg calcium gluconate/kg. Repeated doses may be required to achieve remission of signs. If the i/v route is used the calcium should be given slowly.

Dietary calcium levels need correction with high calcium supplements eg. Nutrobal (Vetark). This can be given at a rate of 0.1g/kg per day over a period of 6-8 weeks or until the problem is corrected. The dose then adjusted to perhaps alternate days. Such supplements are designed for routine long-term supplementation of reptiles. Monitoring of serum calcium levels is advisable. Radiography to monitor progress is also valuable. A calcium level of 2% (on a dry matter basis) seems to be required by iguanas. Vionate (1g/kg per day) plus extra calcium in mealworms, combined with the use of ultra-violet light is also described for long-term maintenance.

Treatment of associated fractures depends on the level of undermineralisation of the bone; severely undermineralised bone needs prior supplementation before intramedullary fixation is used. In the interim, external supports eg. Hexcelite (Hexcel) fitted like a jacket may be useful.

The use of ultra-violet light to convert 7-dehydrocholesterol into the active form of vitamin D is probably important and needs to be taken into account when assessing the level of dietary supplementation required.