A case of zinc toxicity in a galah (Eolophus roseicapilla)

Case history

A 2-year-old female galah (Eolophus roseicapilla) was presented with a 2-day history of inappetence, vomiting, passing loose droppings and a ‘fluffed up’ appearance. t he bird had vomited frequently for the past 2 days but not on the day of examination.

t he bird’s normal diet was varied and consisted of vegetables, pellets, seed, vitamins and willow tree branches. It had been in the owners’ possession since it was fledged. t here were no other aviary birds on the property, and it had not received anthelmintics since it had been in their possession.

t he bird had free range of the property for part of each day so access to unspecified plants in the garden was a possibility. A recently purchased zinc-galvanised cage had some flaking of the coating on it, however the owner felt the bird was becoming unwell prior to arrival of the new cage. Approximately 3 weeks ago a bird toy in the shape of shoe had been purchased from which metal eyelets were now missing.

Clinical findings

on distance examination, the bird was sitting fluffed up in the carry cage. t here was accumulation of bright green faecal material on the feathers around the vent and crusted material in the chest feathers. Prior to closer examination the patient was placed in a darkened, warm, humid environment for 30 minutes to recover from travel and reduce stress. on close examination the bird was in ideal body condition and weighed 265 g. t he crusting in the chest feathers was consistent with vomited crop contents. t he crop was empty. No abnormalities were detected on coelomic palpation. No dyspnoea was present.

t he problems identified from the history and the clinical examination were vomiting, diarrhoea, reduced appetite and lethargy. t he history was indicative of vomiting rather than regurgitation. Differential diagnoses for vomiting include dietary indiscretion (toxins, plants, spoiled food), infections (proventricular dilatation disease (PDD), bacterial, fungal, gastric yeast), psittacosis (Chlamydia psittaci ), heavy metal intoxication (lead or zinc), or metabolic (hepatopathy, sepsis, pancreatitis) (Bowles et al. 2007). In assessing this list, dietary indiscretion

Contact: lisas@vetsouth.co.nz was considered most likely given the free-range time outside, and heavy metal intoxication was quite possible given the damaged toy. PDD is considered to be exotic to New Zealand according to mAF Biosecurity (2009), although it is widely distributed in caged parrots in Australia. Psittacosis was lower on the differential list as this often presents with respiratory as well as gastrointestinal clinical signs.

Diagnostic findings

Based on the differential list, a plan was formulated to check serum biochemistry for metabolic disorders, haematology for evidence of infectious disease, serum concentrations of heavy metal and radiographs for signs of gastrointestinal tract dilation, obstruction and any significant changes to the coelomic organs.

t he patient was pre-oxygenated while being maintained in a warm environment. using a gas mask, light anaesthesia was induced with isoflurane (Isoflurane medsource NZ Ltd, Ashburton NZ) delivered at 2 L/minute via facemask, starting at t he following abnormalities (according to the reference ranges applied) were observed: mild increase in potassium concentration, decrease in creatine kinase activity and decrease in phosphorus concentration. Based on these results, hepatopathy was ruled out and the supportive treatment plan remained unchanged. table 1. s erum biochemistry results measured in-clinic for a female galah with a 2-day history of innappetence and vomiting. c Extrapolated from reference ranges for albumin and globulin d Converted to SI units using the website http://www.endmemo.com/medical/unitconvert t he tests for blood lead and serum zinc concentrations were performed at New Zealand Veterinary Pathology and the results reported 2 and 6 days respectively after the samples were submitted ( table 2). t he serum zinc concentration was so high that it required retesting by the laboratory. t he delayed reporting meant chelation therapy could not be discussed with the owner while the bird was still in clinic.

0.5% and increasing by 0.5% every 30 seconds until a sufficient plane of anaesthesia for radiography was reached at 1.5%. t he patient was stable with an uneventful recovery following blood collection and radiography.

Blood was collected from the right ulnar vein with pressure applied after venipuncture to reduce haematoma formation. As the total volume collected must be <0.5–1% of bodyweight including any haematoma which forms (Doneley 2018), tests had to be prioritised to give maximum information. A serum biochemistry screen ( table 1) was immediately processed inclinic using the Vetscan Avian/Reptilian Profile Plus rotor on the Vetscan VS2 machine (Abaxis Inc. union City CA, uSA) to reduce post-collection artefact (Hoppes et al. 2015). Results were compared to two reference ranges for psittacines as a reference range for Eolophus spp. could not be found. Sufficient blood was collected to allow measurement of lead concentrations in blood and zinc concentrations in serum (New Zealand Veterinary Pathology, Hamilton, NZ). A microhaematocrit sample was assessed in-clinic as having a packed cell volume of 44% (reference rang 38–48%; Adamcak et al. 2000) and a blood smear assessed in-clinic showed no significant abnormalities. t here was insufficient sample to request a full haemogram at the external laboratory.

Lateral and ventrodorsal radiographic views (Figure 1) of the whole bird showed the presence of four radiopaque particles in the ventriculus which had a similar radio-opacity to the metal marker and the metal leg band on the patient. t here was no dilation of the gastrointestinal tract suggesting obstructive disease. t hese observations sent heavy metal toxicosis to the top of our differential list despite not yet having the results of zinc and lead testing.

A crop swab and faecal sample taken a day prior to this consultation had been submitted to Gribbles Veterinary Pathology (mosgiel, NZ). Both samples were submitted for culture (but not cytology). t his revealed a heavy growth of Streptococcus spp. in the faecal sample but no growth from the crop swab. t he presence of Streptococcus spp. in the faecal sample was interpreted as normal faecal flora (Alan Fudge, pers. comm., Veterinary Information Network).

Analyte Measurement (units) Comment from laboratory

Zinc 207 µmol/L Zn levels >30 are diagnostic of zinc toxicity. t his is an extremely high zinc level, compatible with zinc toxicity.

Lead <0.03 mg/L Wildbase, massey university recommends that avian blood lead concentrations should not exceed 0.1 mg/L.

Treatment

While the bird was sedated for blood sampling and radiography, its maintenance fluid requirement (13 mL based on a rate of 50 mL/kg/day) was administered as lactated Ringer’s solution (LRS; Baxter Healthcare Ltd, Auckland, NZ) SC over the dorsum in three sites. A recommendation was made that the bird was hospitalised so that fluid therapy could be continued via crop and/or SC supplementation while the results of final diagnostics were obtained. However, this was declined and treatment as an outpatient was initiated with 0.5 mg/kg metoclopramide (metoclopramide HCl; Baxter Healthcare Ltd, Auckland, NZ) given orally 2–3 times daily, with oral electrolytes (oralade; macahl Animal Health Ltd, uK). While there are no pharmacokinetic studies, there are anecdotal recommendations to use metoclopramide to improve crop motility and control regurgitation (Bowles, 2007). t he plan was that if vomiting continued and or fluid intake was insufficient then the patient would be admitted to the hospital.

t he patient was re-examined and admitted to hospital the following morning as it was not drinking at home. Supportive treatment started with oral fluid therapy as protracted vomiting was not occurring. If oral fluids were insufficient then the next option would have been intermittent SC fluids, followed by IV or intraosseous access if needed. maintenance fluid requirements had been calculated at 13.25 mL/day and the bird was estimated to be 5% dehydrated after 24 hours at home with minimal fluid intake. Aiming to replace the first 50% of the dehydration loss within the first 24 hours, this gave a goal of 20 mL fluids/day plus any ongoing losses. t he estimated safe crop volume for medium parrots is 10–15 mL and large parrots is 20–30 mL (Lisa Argilla, pers. comm.; Wismer 2009). t he fluids were administered to the galah at a rate of 5 mL every 2–3 hours which was well within the crop volume guidelines. LRS was selected for the first two doses of crop fluids. When this was tolerated with no vomiting, oralade was added in a 1:1 ratio to the LRS for the next two feeds. t here was no vomiting through day 1 of hospitalisation and by later in the day the patient was starting to eat fruit and vegetables out of the nurses’ hands. No vomiting was observed at any stage while in the hospital. During day 2 of hospitalisation, oral fluid supplementation using oralade and LRS in a 1:1 ratio for a total of 20 mL was repeated. t he patient continued to eat when hand fed and later in the day started voluntarily drinking as well. t he faeces were still bright green but the urates were white. Body weight remained stable at 265 g. t he patient was discharged for supported feeding at home while we awaited the results of the heavy metal testing. Follow-up phone calls with the owner confirmed that the bird was drinking well with an improving appetite but was still quiet. t he faeces continued to gradually return to their normal colour and consistency.

Six days after the initial presentation, the serum zinc concentration was reported as 207 µmol/L consistent with zinc toxicity. For recommendations for treatment for zinc toxicity see Box 1. By the time the zinc results were available, the owner reported that the bird’s behaviour, eating and drinking habits had returned to normal. t hey declined another hospital admission and more intensive therapy at this stage. t he decision was made to start ½ teaspoon psyllium (metamucil, Procter & Gamble, Auckland, NZ) daily, added to 60 mL baby food, diluted peanut butter or fruit and vegetables to encourage metal items to pass through the gastrointestinal tract.

Box 1. Treatment recommendations for heavy metal toxicosis in birds (Green 2004)

1. Fluid therapy with LRS to prevent renal damage from dehydration and potential chelation toxicosis, and to offset the fluid loss due to polyuria. Fluid rates of up to 100 mL/kg/hour are recommended and the oral route can be used if gastrointestinal tract is working.

2. Warm environment of 28–30°C with a humidification source.

3. Chelation therapy – administration of an agent that binds to zinc forming non-toxic complexes which can then be excreted.

4. Catharsis (e.g. psyllium) to encourage metal items to pass through the gastrointestinal tract.

5. If seizures develop, then use of diazepam may need to be considered.

A plan was made to repeat the measurement of serum zinc concentration and radiography 2.5 weeks after the initial presentation to see if the zinc particles had been excreted, if the zinc concentration was reducing and revisit whether chelation therapy was required. At this revisit, the bird had maintained its weight and had no history of further vomiting or diarrhoea. Radiography showed only one radiopaque particle remaining in the ventriculus. t he serum zinc concentration had reduced from 207 µmol/L to 48.7 µmol/L, consistent with the reduced amount of radiopaque material in the ventriculus (assuming that this material had contributed to the zinc toxicosis). Based on this improvement, chelation therapy was not pursued. Addition of psyllium to the diet was continued for a further 2 weeks. t he patient made an uneventful recovery and no further monitoring was performed.

Discussion

Just as with other veterinary species, the first step of managing and treating a sick bird is a thorough history and clinical examination to allow differential diagnoses to be considered and the most appropriate diagnostic tests to be performed. Distance examination and minimising stress prior to and during handling are even more important in birds than other veterinary species.

With regards the differentials under consideration for this case, infectious causes (e.g. by food contamination), toxins (heavy metal, plants, other environmental contaminants), foreign body ingestion, pancreatitis, secondary causes of vomiting such as hepatic or renal disease, were all under consideration. Parasitism seemed less likely differential given the bird was not in an aviary situation and exposed to frequent faecal contamination in the environment, however given it had some outdoor access, this could not be completely discounted. Pancreatitis in birds is rarely documented antemortem but should be suspected in birds showing abdominal pain or gastrointestinal dysfunction. Similar to mammals, hyperamylasaemia can be suggestive of pancreatitis, but it is not present in all affected birds and amylase is not included on the Vetscan Avian/ Reptilian rotor.

A crop swab and faecal sample collected the day prior to the initial consultation were submitted for bacterial culture. In retrospect, rather than a culture of the crop contents, a swab would have yielded more information faster. Alan Fudge recommends swabbing the crop with a saline-moistened swab and using this to make a saline wet mount, followed with a Gram's stain. t his can be used to look for bacteria, yeasts and flagellates such as Giardia or Trichomonas in some bird species. Gram staining of fecal smears are a commonly used tool in parrots to assess enteric health with low numbers of Gram-positive bacteria predominating in the healthy psittacine gastrointestinal tract. Evans et al. (2014) looked at the agreement of faecal Gram stains with culture results in 21 healthy parrots and found that Gram's stains and bacterial culture may need to be performed with a parallel testing strategy to limit the likelihood of misclassifying the microbial flora of psittacine patients. Performing a faecal Gram stain would have been a quicker way of identifying if there was bacterial overgrowth and if antibiotics or other diagnostic work-up was indicated while waiting for the culture results. A faecal egg count could also have been performed to see if there was any indication for anthelmintic treatment.

By the time the test results indicating zinc toxicosis was received, the patient was clinically improving. t he movement of metal particles through the gastrointestinal tract of a bird is very different to that of a mammal (Green, 2004). t he ingested particles are often trapped with the ventriculus contents and are gradually ground into smaller particles, creating a greater risk of metal poisoning for birds. Lead and zinc toxicosis can produce similar signs affecting multiple organ systems including the gastrointestinal tract, nervous system, kidneys and haematopoietic system. Zinc is not sequestered in bone or other tissue like lead, so once it is cleared from the gastrointestinal tract there is no concern about mobilisation from bone increasing circulating concentrations again months after the initial ingestion. Zinc toxicosis is more often seen in caged birds due to more potential sources of zinc being available domestically. Clinical signs can include regurgitation, diarrhoea, anorexia, lethargy, depression, ataxia, seizures, feather picking, polyuria/ polydipsia, anaemia and sudden death.

Diagnosis of zinc toxicosis may be supported by presence of hypochromic microcytic anaemia, increased alanine aminotransferase (ALt ) activity and increased blood glucose. Interestingly these anomalies were not recorded in this case – however the Vetscan Avian rotor does not measure ALt activity. Zinc is an essential dietary trace element and some amount of zinc is expected to be present in the serum of healthy birds however it should be <30–55 µmol/L depending on the reference range used by the reporting laboratory (NZVP, Lisa Argilla, pers comms.). t he concentration recorded in this galah (207 µmol/L) could therefore be considered extremely high. When reviewing the management of this case, daily weighing of the patient was a useful tool. It also would have been ideal to have weighed any food or water left in the cage so that the actual voluntary intake could be calculated. t here was not an effective assessment of whether the bird had abdominal pain which required analgesia (e.g. butorphanol). Fluid therapy was appropriate for maintenance and to correct for fluid losses from vomiting. Birds should not be fasted due to their high metabolic rate and energy requirements (Doneley, 2001), which is why oralade was added into the oral fluids to replace electrolytes and some energy until the patient was eating. t he galah’s serum zinc concentrations were high enough initially that starting chelation therapy would have been appropriate. However, as it was starting to improve when the diagnosis was confirmed, the owners declined this treatment and opted to retest and monitor. When the zinc concentration was re-checked, it had dropped from 207 µmol/L to 48.7 µmol/L; chelation therapy was still justifiable (but again declined). Recommendations for chelation therapy are to administer calcium EDtA at a dose of 25–50 mg/kg Im every 12 hours for 5 days then reassess serum zinc concentrations 2 days later and repeat the treatment if needed (Lisa Argilla, pers. comm.). Calcium EDtA can be compounded by a veterinary compounding pharmacy (e.g. optimus Healthcare Ltd, Penrose, Auckland NZ) to give a volume suitable for injection into the patient. While receiving chelation therapy, supportive treatment with fluids, warmth and rest are important.

Conclusion

Heavy metal intoxication should always be considered in any bird showing gastrointestinal signs. Zinc toxicity is more common than lead toxicity in pet birds due to more exposure to this metal within their living environment. management of avian cases is possible and rewarding in general practice: just follow the same process as for all other patients – a good history, a diagnostic plan and supportive care while the treatment plan is sorted.

Acknowledgments

t hanks to Lisa Argilla (Wildlife Hospital Dunedin) for taking the time to discuss this case and her recommendations regarding zinc toxicosis management in parrots.

Relevant Reading

Adamcak A, Hess LR and Quesenberry KE. Intestinal string foreign body in an adult umbrella Cockatoo (Cacatua alba). Journal of Avian Medicine and Surgery 14, 257–63, 2000

Bowles H, Lichtenberger M, Lennox A. emergency and critical care of pet birds. Veterinary Clinics of North America: Exotic Animal Practice 10, 345–94, 2007

Doneley RJT. Acute pancreatitis in parrots. Australian Veterinary Journal 79, 409–11, 2001

Doneley RJT. Clinical Pathology of Exotic Pets. https:// www.vin.com/apputil/content/defaultadv1. aspx?pId=22915&catId=124640&id=8896524 (accessed 16 April 2023). World small Animal Veterinary Association Congress proceedings, 2018

Evans EE, Mitchell MA, Whittington JK, Roy A, Tully TN. measuring the level of agreement between cloacal Gram's stains and bacterial cultures in Hispaniolan Amazon parrots ( Amazona ventralis). Journal of Avian Medicine and Surgery 28, 290–6, 2014

Green C. Heavy metal toxicoses in birds. Companion Animal Society Newsletter 15 (3), 24–8, 2004

Hoppes SM, Boyd JD, Brightsmith DJ. Impact of delayed analysis in avian blood biochemical values measured with the Abaxis Vets can Vs2. Journal of Avian Medicine and Surgery 29, 200-9, 2015

Lumeij JT, Overduin LM. plasma chemistry references values in psittaciformes. Avian Pathology 19, 235-44, 1990

MAF Biosecurity New Zealand. Import Risk Analysis: Psittacine Hatching Egg s draft, pp 62–5, https://www.mpi.govt.nz/ dmsdocument/6076-psittacine-hatching-eggs-draft-import-riskanalysis-august-2009, (accessed 19 April 2023). Wellington, NZ, 2009

Wismer T. Managing Toxicoses in Exotic Animals. Wild West Veterinary Conference 2009, 2009 l t his article was written as part of the requirements for receiving the Dechra/CAV "A week with ..." scholarship

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