title: Pathology of runting in farmed saltwater crocodiles (Crocodylus porosus) in Australia.
abstract: Extremely poor growth of some individuals within a birth cohort (runting) is a significant problem in crocodile farming. We conducted a pathological investigation to determine if infectious disease is associated with runting in farmed saltwater crocodiles (Crocodylus porosus) and to look for evidence of other etiologies. In each of 2005 and 2007, 10 normal and 10 runt crocodiles, with an average age of 5.5 months and reared under identical conditions, were sampled. Laboratory testing included postmortem; histological examination of a wide variety of tissues (with quantitation of features that were noted subjectively to be different between groups); hematology; serum biochemistry (total protein, albumin, globulins, total calcium, phosphorus, and iron); bacterial culture of liver and spleen (2005 only); viral culture of liver, thymus, tonsil, and spleen using primary crocodile cell lines (2007 only); and serum corticosterone (2007 only). The only evidence of infectious disease was mild cutaneous poxvirus infection in 45% of normal and 40% of runt crocodiles and rare intestinal coccidia in 5% of normal and 15% of runt crocodiles. Bacterial and viral culture did not reveal significant differences between the 2 groups. However, runt crocodiles exhibited significant (P < .05) increases in adrenocortical cell cytoplasmic vacuolation and serum corticosterone, decreased production of bone (osteoporosis), and reduced lymphoid populations in the spleen, tonsil, and thymus. Runts also exhibited moderate anemia, hypoalbuminemia, and mild hypophosphatemia. Taken together, these findings suggest an association between runting and a chronic stress response (hyperactivity of the hypothalamic-pituitary-adrenal axis).
authors.affiliation: Berrimah Veterinary Laboratories, Department of Primary Industry and Fisheries, Northern Territory Government, Berrimah, Northern Territory, Australia cathy.shilton@nt.gov.au.
authors.forename: C
authors.initials: C
authors.lastname: Shilton
authors.affiliation: The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: G P
authors.initials: GP
authors.lastname: Brown
authors.affiliation: Berrimah Veterinary Laboratories, Department of Primary Industry and Fisheries, Northern Territory Government, Berrimah, Northern Territory, Australia.
authors.forename: L
authors.initials: L
authors.lastname: Chambers
authors.affiliation: Berrimah Veterinary Laboratories, Department of Primary Industry and Fisheries, Northern Territory Government, Berrimah, Northern Territory, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Benedict
authors.affiliation: Berrimah Veterinary Laboratories, Department of Primary Industry and Fisheries, Northern Territory Government, Berrimah, Northern Territory, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Davis
authors.affiliation: Berrimah Veterinary Laboratories, Department of Primary Industry and Fisheries, Northern Territory Government, Berrimah, Northern Territory, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Aumann
authors.affiliation: The University of Sydney, Sydney, New South Wales, Australia Porosus Pty. Ltd., Noonamah, Northern Territory, Australia.
authors.forename: S R
authors.initials: SR
authors.lastname: Isberg
mesh_terms: D000489:Alligators and Crocodiles / Q000254:growth & development*; D000818:Animals; D017756:Aquaculture; D001315:Australia; D001772:Blood Cell Count / Q000662:veterinary; D001774:Blood Chemical Analysis / Q000662:veterinary; D001835:Body Weight; D015331:Cohort Studies; D005260:Female; D008297:Male; D010913:Pituitary-Adrenal System / Q000503:physiopathology; D012623:Seawater; D013154:Spleen / Q000503:physiopathology; D013312:Stress, Physiological
keywords: adrenocortical hyperplasia; crocodile; farmed; histopathology; inanition; lymphoid atrophy; runting; stress