Abstract

A dead five-year-old leucystic American alligator was presented to the University of Florida, College of Veterinary Medicine aquatic animal research laboratory for necropsy. Gross necropsy showed only mild inflammation of the proximal small intestine, apparent fibrosis of the kidney, and mild congestion of the lungs. Organ samples were submitted to histopathology and also to ABC Research Corp. for metal and nutrient analysis. A blood sample was submitted for microbiology. Organ sample histopathology showed some liver fibrosis and inflammation, but no lesions were detected that would result in sudden death. Clostridium sp. was found in the blood culture and clostridia infection was the assigned cause of death.

Introduction

A female leucystic alligator approximately 5 years in age was presented to the University of Florida, College of Veterinary Medicine aquatic animal research laboratory for necropsy. This animal was originally captured wild in July 1994, 4 months before it was donated to the Audubon Zoo. The estimated hatch date was September 1994. It was in apparent good condition at the time of acquisition but had not been eating well. The animal was nearly pure white in color, except for the eyes, which were blue-gray in color, and it also had greenish marks over the left eye and between the eyes.

This animal was housed at the Audubon Zoo until January of 1999 when it was transferred to Gatorland Zoo in Orlando, Florida. This animal had a history of health problems at the Audubon Zoo. It was treated for ulcerative dermatitis on numerous occasions in 1996, and for a suspected bacterial disease in 1997. A culture from the dermatitis was found to be E. coli. This was successfully treated with antibiotics (Baytril). The suspected bacterial infection reported in 1997 was treated with Amikacin. There were no reported problems with the animal in 1998. It had been moved from display due to renovations at the Audubon Zoo in the area of its enclosure. The animal died February 9, 1999 at Gatorland Zoo, one month after shipment from Audubon Zoo. It had eaten the day before at 6:30 PM and was found dead in its pen 7:30 AM the following morning. A necropsy was performed at 5:30 PM, less than 10 hours post-mortem to determine the cause of death.

Necropsy & Results

Upon presentation, the animal was weighed and measured. It was 130 cm in length, and weighed 6.91 kg. There were no lesions present on the exterior of the body, and the animal was considered to be in good condition (6.6% body fat). A ventral mid-line incision running cranial-caudal was made from the pectoral girdle to 2 centimeters cranial to the cloaca. A red tinged fluid was present in the body cavity. All internal organs appeared normal from a visual inspection. The liver was a pale light brown in color but the nutrient analysis was considered normal (moisture 78%, protein 13.5%, fat 6.2% and ash 1%). The kidneys were somewhat hard and fibrous upon inspection. Inflammation was present in the proximal small intestine in the area of the duodenum. Mild congestion of the intestine was noted throughout its length but no parasites were found. No other gross anatomical abnormalities were noted.

Histopathology of ovary, intestine, liver, heart, kidney, lung, and spleen were performed at the University of Florida Veterinary Medical Teaching Hospital pathology laboratory. No abnormalities were found in the ovary, heart, or spleen. Moderate chronic locally extensive fibrosis was found in the liver. Acute moderate diffuse congestion and acute multi-focal mild tubular necrosis was found in the kidney. Acute diffuse mild congestion was found in the lungs. The large and small intestines were found to have mild sub-acute multi-focal lymphocytic enterocolitis with prominent lymphoid tissue. The changes did not indicate the cause of sudden death in the animal. Prominence of lymphoid tissue in the intestines suggested up-regulation of the immune system.

Tissue submission to ABC Research Corp. did not show any evidence of significant heavy metal concentration. Lead, mercury, arsenic, cadmium, and zinc levels were within safe ranges for liver and kidney. The following levels were those extracted from the liver and kidney of this animal.

Clostridium sp. was cultured from blood. No blood-born parasites were seen in a direct smear. Clostridium is the second most common bacterial pathogen of the alligator¹ and is the assigned cause of death for this animal. This alligator had a history of bacterial infections in the past and it is possible that the prior infections had either never completely resolved or that a new infection was present. Stress from the transfer could have been a factor as well. It is assumed that this animal was immunologically weak, and any stress could have allowed opportunistic bacteria to overwhelm the animal quickly. A prior necropsy of an albino alligator that died from bacterial disease was judged to be immunologically compromised², which is a possibility in this animal.

Acknowledgements

Thanks to pathology and microbiology laboratories at the University of Florida Veterinary Medical Teaching Hospital for their assistance. Also thanks to Dr. Roberto Aguilar and the Audubon Park Zoo for providing the animals' health records.

References

1.  Barnett JD, PT Cardeilhac. 1995. Clinical values associated with opportunistic bacterial diseases in farm raised alligators. Proceedings of the International Association for Aquatic Animal Medicine, P. 22.

2.  Floyd GM, K Marshall, J Wolf, J Barnett, PT Cardeilhac. 1996. Fatal Aeromonas Infection in an Albino American Alligator. Proceedings of the International Association for Aquatic Animal Medicine, P. 53.