Case Report - Black Swan (Cygnus atratus)

History

An adult Black Swan was found by a member of the public on a lake in Pakenham.  It looked unwell and was taken to the Australian Wildlife Health Centre for assessment.  

Clinical Examination

On examination the swan was emaciated and very weak.  It has considerable difficulty standing and holding up its head. There were no obvious signs of trauma.  The bird was force-fed and started on antibiotics in case it had a bacterial infection, and also given an anti-fungal medication, as water birds commonly develop fungal infections in captivity.  

Diagnostic Tests

As water birds can carry avian influenza, the bird was swabbed and tested, but the result was negative.  Blood was taken to check lead levels and also tests for botulism, as both frequently cause weakness and depression in water birds.  The blood lead level was found to be extremely high. 

Diagnosis

Lead poisoning. 

Treatment

The bird was treated with Calsenate, which binds up any lead in the blood, prevents it from reaching the brain and leads to the rapid removal of lead from the body.  Unfortunately the disease in this swan was too far advanced and it did not respond to treatment and died.  At post-mortem examination two lead balls were found in the bird's gizzard.  

Conclusion

Unfortunately lead poisoning still occurs, mostly in water birds.  Discarded fishing sinkers and lead shot are common causes of poisoning.  These are accidently eaten while the birds dabble in the mud looking for food. 

Lead poisoning can be treated successfully if caught early enough.  Unfortunately wild birds are often very difficult to catch until they are extremely sick.  This means that many birds arrive in the last stages of the disease, making treatment very difficult.  Birds that are shot do not develop lead poisoning.  The pellets can cause significant damage and potentially kill the bird, but if they don't hit any vital structures they will sit in the muscles or abdomen and not cause any problems.