Abstract

Three major disease problems which occurred in groups of alligators hatched in 1982 and 1983 on Florida alligator farms were investigated. The first investigation concerned an outbreak of metabolic bone disease that resulted from feeding boneless turkey without mineral supplementation. Clinical signs included reduced feed consumption, lethargy, toes curled upward, inability to use hindlimbs, and spontaneous fractures. Loss of bone mineral and spontaneous "green stick" fractures were seen in radiographs. Infestation with larvae of Sebekia oxycephala caused a second major disease problem. Clinical signs were anorexia, weight loss, and respiratory distress. Live mosquito fish were the source of this parasite and the mobile larvae caused tissue damage and hemorrhage, and severe mechanical damage to the lungs. The third disease problem occurred in a group of 1000 hatchlings following cold shock. Over 90% of these animals died over a two year period. Clinical signs were cachexia, slow growth, and death. Five hatchlings were selected for microbiologic and pathologic study. Hyphae consistent with Paecilomyces spp. were observed within granulomatous lesions of the kidneys and lungs. Fungi were cultured from the lesions.

Introduction

Crocodilians have been hunted for their hides for hundreds of years, however, within the last quarter century, hunting pressures and human population increases have drastically reduced crocodilian habitats and numbers. In order to maintain a supply of hides and consequently an industry, attempts have recently been made to farm crocodilians.

The intensive culture of these animals has produced disease conditions not previously reported for wild animals. In the present report, we consider the 3 most important disease problems that we encountered in Florida alligators hatched in 1982 and 1983. Most alligators hatch in Florida on 1 September ± 15 days; September is month 1 of culture.

Materials, Methods, and Results

Case Histories Metabolic

Bone Disease (1)

An outbreak of metabolic bone disease occurred in a group of 298 hatchlings owned by a farm located near Avon Park in South Central Florida.  Fire destroyed the freezer and cooler used in feed storage during month 7 of culture (March) and the hatchlings were fed boneless turkey purchased at a local market. During month 10 of culture (June), after 90-120 days of being fed boneless turkey, the hatchlings began to show signs of lethargy, poor appetite, locomotor difficulty, and deaths.

In month 11 of culture (July), the hatchlings were lethargic, unable to use their hindlimbs, their toes were curled upward, and the mandible and maxilla could be easily deformed (rubber jaw). Three (3) animals showing typical symptoms were submitted for examination. Radiographs of the animals showed the following: 1) marked cortical thinning of the long bones; 2) multiple folding (green stick) fractures involving most long bones; 3) well-defined but poorly mineralized periosteal new bone growth adjacent to the fractures; 4) a compression-type of fracture in the proximal third of the cervical vertebrae; 5) low bone density of the ribs and skull (teeth had the appearance of floating in a cartilaginous model).  Histological preparations were made in a routine manner and stained with hematoxylin and eosin. Microscopic examination demonstrated cortical thinning and remodeling of long bones with evidence of callus formation at previous sites of fracture. The diet of these hatchlings was changed to ground beef, whole chicken, and whole fish supplemented with a standard vitamin mineral supplement used in turkey rations. Hatchlings showing clinical signs were given 30 mg/kg body weight oxytetracycline by stomach tube. Most animals began to eat 3 days following medication, but 128 animals of the group of 298 died from this disease outbreak. Pentastomiasis (2)

Pentastomiasis caused by larvae of Sebekia oxycephala, occurred in a group of 30 hatchlings 4 weeks of age being fed catfish heads, crickets, and live mosquito fish, Gambusia affinis. Clinical signs included were anorexia, weight loss, respiratory distress, and death.

Inflamed hemorrhagic lungs and larvae (7.0; SID +/- 2.3) were observed grossly in the lungs of all animals examined. Microscopic examination of tissues revealed pulmonary hemorrhage, hepatic lipidosis, collapsed air sacs, and parasites in the pulmonary and hepatic parenchyma.

An examination of individual components of the diet showed that mosquito fish were the source of the larvae. Feeding of the mosquito fish to control animals produced infection with the larvae and clinical signs similar to those seen in the hatchlings with natural infections. Clinical signs of disease disappeared from infected hatchlings within 4 weeks following removal of mosquito fish from the diet and changes in husbandry techniques.

Paecilomyces Infection

Approximately 1000 hatchling alligators were purchased in September 1982 by an alligator farm in North Central Florida (Keystone Heights, FL). The farm used intensive culture techniques and was designed to maintain hatchlings at a constant temperature of about 32ºC.

The hatchlings were kept through month 4 (January) of culture in 50 cm² tanks, 30ºcm deep with 20ºcm of deck and 30ºcm of water. A growth diet consisting of approximately equal parts of beef, poultry, and fish with a vitamin-mineral supplement was fed. After month 4, the hatchlings were moved to larger indoor tanks, but because of problems with the heating system, the animals could not be heated after month 4 of culture.

The animals did not grow well after heat loss, and during month 7 (March), deaths of up to 5 animals per day began to occur. Deaths continued over a 2 year period, until over 900 losses were recorded in the group of 1000 animals.

The hatchlings were cachectic and appeared "hunched up" or contracted on gross examination. Necropsies were performed on 7 animals. Yellow, soft foci varying in size were found within the lungs upon gross examination. One animal had similar small foci located within both kidneys.

Microscopic examination of affected lungs indicated multifocal granulomas. The granulomas were composed of a central core of degenerating heterophils surrounded by multinucleated giant cells. Septated mycelin 2-4 microns wide containing conidiophores and characteristic of Paecilomyces spp. were seen centrally within granulomas stained with silver stains.

Microscopic examination of the kidneys showed occasional tubules that were dilated and contained a mucinous secretion laced with heterophils, debris, and bacteria. Several areas of the kidneys were replaced by granulomas similar to those seen in the lungs. Fungi identified as Paecilomyces sp. were isolated from cultures of the granulomas.

Discussion

Intensive culture of alligators is a new industry in the field of aquaculture. Many of the farmers have never cultured a reptile before; thus, mistakes in husbandry practices may occur. Metabolic bone disease has been reported in zoo animals (1) and it is now apparent that hatchling alligators which increase in weight as much as 6% per day require whole animals (bones), bone meal, or a calcium supplement (calcium carbonate - 1.0 %; calcium diphosphate - 0.9%) (3,4) to the diet.

The problem of getting hatchling alligators to eat led to the present problem of pentastomiasis. A hatchling is inherently attracted to live moving prey and many farmers start them eating with live crickets or minnows. In this case, the minnows carried larvae of S. oxyceplala (5). Although infestations of this parasite occurs in wild alligators (6), clinical disease has never been reported. The condition can easily be managed by freezing the fish at -10 C for 72 hours which will kill the larvae. Farmers should also avoid the use of live moving prey to induce the start of feeding in hatchlings.

Cold shock in hatchlings was also an artifact of captive rearing. The confined animals were abruptly exposed to temperatures more than 20 degrees colder than their accustomed culture temperatures. In conditions of artificial culture, the animals are unable to seek natural protection from the cold.  Stress of this type is known to permit infections with opportunistic organisms present in the environment (7) -- Paecilomyces sp. was one of the opportunistic organisms in this outbreak.

References

1. Wallach, J.D. Feeding and nutritional diseases of reptiles. In Zoo and Wild Animal Medicine, M.E. Fowler, ed. W.B. Saunders, Philadelphia, 1978
2. Telford, S.R., and Campbell, H.W. Parasites of the American alligator, their importance to husbandry, and suggestions toward their prevention and control. In: proceedings of the First Annual Alligator Production Conference, February 12-13, 1981, pp. 46-51 (1981).
3. Cardeilhac, P.T. Nutritional Diseases of Alligators. In: Proceedings of the First Annual Alligator Production Conference, P.T. Cardeilhac, T.J. Lane, and R.E. Larsen, eds. IFAS, University of Florida, Gainesville, FL, pp. 58-64 (1983).
4. Cardeilhac, P.T. Mineral metabolism. In: Textbook of Physiology, J.E. Breazile, ed. Lea and Febiger, Philadelphia, pp. 451-455, 1972.
5. Vernard, C.E. and Bangham, R.V. Sebekia oxycephala (Pentastomida) from Florida fishes and some notes on the morphology of the larvae. Ohio J. Sci. 41(l): 23-28 (1941)
6. Cherry, R.H. and Ager, A.L. Parasites of American alligators (Alligator mississippiensis) in South Florida. J. Parasit. 68(3): 509-510 (1982).
7. Jacobson, E.R. Viral and fungal diseases of alligators. In: Proceedings of the First Annual Alligator Production Conference, P.T. Cardeilhac, T.J. Lane, and R.E. Larsen, eds. IFAS, University of Florida, Gainesville, FL, pp. 42-45