Hyperplastic goitre and mortality in captive-reared black stilts ( Himantopus novaezelandiae ).
OBJECTIVE
To study the gross, histopathological and clinico-pathological findings in cases of hyperplastic goitre in sub-adult captive- reared black stilts following their release on riverbeds in the south Canterbury region of New Zealand.


METHODS
Necropsies were undertaken on the recovered carcasses of 48 black stilts over a 3-year period (1997-1999). The cause of death was determined, and thyroid glands were examined histopathologically and compared with those of free-living pied stilts. Concentrations of triiodothyronine (T3) and thyroxine (T4) in the serum of sub-adult and adult stilts were measured before and after iodine supplementation.


RESULTS
The main causes of death of captive-reared black stilts following release were trauma, predation and starvation. An increase in size of the thyroid gland due to follicular hyperplasia and dilation was seen in all birds with intact thyroid glands (n=27). Dysplastic follicular changes such as epithelial desquamation, lipid deposition and haemorrhage were common in a large proportion of individuals with goitre. Dietary supplementation with iodine greatly improved survival rates in sub-adults following release, and significantly increased concentrations of T3 and T4 in serum.


CONCLUSIONS
Subclinical goitre due to thyroid hyperplasia and dysplasia was the cause of hypothyroidism and this contributed to the poor survival of released sub-adult black stilts raised in captivity. Iodine supplementation of the diet of captive adults and sub-adults resulted in increased concentrations of T3 and T4 in serum and improved survivability.
Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand. m.r.alley@massey.ac.nz
M R
MR
Alley
C M
CM
Twentyman
S E
SE
Sancha
P
P
Clark
R F
RF
Maloney
D000818:Animals; D000835:Animals, Wild; D001715:Bird Diseases / Q000097:blood / Q000401:mortality* / Q000473:pathology; D001717:Birds; D003247:Conservation of Natural Resources; D006042:Goiter / Q000401:mortality / Q000662:veterinary*; D006965:Hyperplasia / Q000401:mortality / Q000662:veterinary; D009520:New Zealand / Q000453:epidemiology; D013961:Thyroid Gland / Q000473:pathology; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D014284:Triiodothyronine; D013974:Thyroxine