Numbers of swans treated for lead poisoning
Currently out of a yearly throughput of 3000 Mute swans we treat about 6 per month (around 72 per year) for lead poisoning. This is in contrast to before the Control of Pollution ( Angler’s Lead weights) Regulations 1986 when 86% of cases required treatment For lead poisoning (although the yearly throughput was lower).
Initial diagnosis of lead poisoning
Our diagnosis and treatment is based almost solely on clinical signs and response of clinical signs to treatment.
Many birds can tolerate very high background blood levels of lead with no clinical signs making laboratory estimations impossible to interpret or use. I am sure you are aware of the studies carried out by Dr. Jane Sears and colleagues at the Edward Grey Institute, Dept. of Zoology, Oxford.
Response to treatment can give a result more quickly than a laboratory result turnaround.
The only times we have obtained blood lead estimations recently are when we have needed evidence of lead poisoning to support the clinical signs for reasons other than therapy.
We do carry out radiography of the abdomens of suspected lead poisoning cases to assess presence of radio-opaque objects in the gizzard and extent of gut impaction and gizzard enlargement. The well-known limitations apply, such as the opacities not necessarily being lead, or being only lead coated, or lead poisoning being present even in the absence of lead in the gizzard We do occasionally find a foreign body which we remove, such as the odd metal lure or 15cm long metal spiky thing.
At the risk of being accused of teaching any cider female member of my family to suck eggs, the main signs of lead poisoning are:
Flaccid limb paralysis, usually bilateral; Kink in neck;
Bright green diarrhoea;
Noticeable in the oesophagus of the lower neck when very severe passing of undigested food in faeces;
Ataxia, recumbence, loss of righting reflex, coma, convulsions, especially in cygnets;
“Diamond eye” where the aperture of the eyelids forms a diamond instead of an oval;
Inappetence lethargy and weight loss:
Gaping on respiration.
The main differentials are:
Trauma caused by flying accident, humans, dogs, foxes or mink – any available history, site of rescue, signs of wounds all very important. Dislocated neck can give kink but can palpate a specific site of dislocation;
Botulism – lead poisoning often more apparent in colder seasons, Botulism confined to very hot dry periods. Botulism outbreak often manifests as massive die-off on area of water, including many other water fowl, other birds, fish and vegetation;
– bird often looks sicker and more miserable with Botulism – with lead can look remarkably bright despite all its problems!
– neck often thrown right over back to lie with beak touching dorsum between wings with Botulism;
– salivation with thick mucous consistency with Botulism – “cacky mouth” leading to “cacky back”
– flaccid limb paralysis tends to involve all limbs in Botulism, whereas can involve wings but bird still able to stand with plumbism;
– don’t get same food non-digestion or bright green faeces with Botulism;
– don’t get cephalic oedema or diamond eye with Botulism.
Other causes of inappetence and weight loss – usually bright green diarrhoea and nervous signs enough to distinguish.
I am headily glad you don’t mention gizzard washout under anaesthesia as this is detrimental to the bird. We only anaesthetize leaded birds if absolutely necessary (e.g. to perform a coeliotomy to retrieve a 15cm long metal spiky thing…).
Anaesthetic recovery times in leaded birds are considerably prolonged. We treat according to severity of clinical signs and response to treatment until clinical signs have resolved and the bird is thriving.
All birds are given antibiotic cover by injectable Clamoxyl LA or Baytnl. Inappetent birds are given Vitamin B 12 injections. We do not routinely worm birds but would give any stunted cygnets or juveniles injected Ivomec or oral Panacur.
Generally speaking we find stomach tubing very stressful for the birds and prefer to encourage them to eat and provide intravenous fluid support.We used to give subcutaneous sodium calciumedetate but it is often ineffective. For cases of any severity we start treatment with a 24 hour intravenous dose of EDTA (Animalcare, 250mg/mI) of 6m1 for a 10kg bird in IL Hartmann’s solution, with Duphalyte if the bird is inappetent. This may be followed by a second similar 24 hour EDTA/Hartmann’s drip, or intramuscular injections, the dose of which depends on initial signs and response over the first 24 hours. An initial 3-day course will be followed by three days off EDTA but on any supportive care. Again, subsequent EDTA courses length, frequency and proximity depend on clinical signs.Some birds present with a slight neck kink and mild plumbism signs despite large pieces of radio-opaque material being in the gizzard. These are lead-coated pieces of metal, and the lead poisoning resolves over 24-48 hours with a low dose of EDTA.
Birds often need less intensive supportive care for some time after treatment and so stay in our outside treatment pens until fit for release.
Mrs Sally L. Goulden BvetMed, MRCVS
Veterinary surgeon to The Swan Sanctuary