Abstract

Sixteen alligators ranging size from 189 to 282 cm in length were captured in the Conservation areas of the Everglades. The animals were weighed, measured and blood samples were collected for the determination of complete blood counts (CBC), serum chemistry and protein electrophoresis. The clinical values were compared with the same values determined for alligators hatched from eggs collected in the Everglades and Southern Louisiana and raised in captivity. Values from 40 tests run on each of the three groups were compared using ANOVA. The values from both captive groups were similar but the wild Everglades alligators had significant differences in several of the tests and particularly in the serum globulins. The condition of the animals and the changes indicated chronic inflammation in the wild Everglades alligators.

Introduction

The American alligator (Alligator Mississippiensis) is an important animal in terms of economics for the southern states economy and also in terms of the natural environment as a top predator. In an effort to study the physiology of this animal, routine blood samples have been collected for several years in order to set the normal parameters for a captive raised healthy alligator. The setting of standards for healthy alligators will enable clinicians and researchers to determine variations from normal values of alligators that are debilitated either from disease, parasitism toxins, or malnutrition.

Materials and Methods

A series of forty different tests were run on blood collected from the alligators. These tests included a complete blood count (CBC), full blood chemistry profile, and protein electrophoresis. All the animals tested for the establishment of normal values for clinically healthy alligators were held at Gator land Zoo in Orlando, Florida. The subject animals were all hatchlings that were raised from eggs incubated at the University of Florida, College of Veterinary Medicine. The eggs were collected from captive Gator land Zoo alligators, Louisiana alligators from the Rockefeller Refuge, and eggs collected from the Everglades National Park. All eggs were cleaned after collection and disinfected with 1% Nolvasan prior to hatching.

After hatch, the animals were delivered to Gator land zoo and held in enclosures measuring one meter square, varying from 0.3m to 0.48m deep. The deeper end holds water that is under constant flow. Air temperature is held at 31.6 degrees C. The animals are fed a mixture of horse meat supplemented, with 55% protein meal, containing vitamins, minerals, free amino acids, and Oxytetracycline at 250 ppm, and Virginiamycin at 60 ppm for the first six months of life. No more than 15 alligators are held in one enclosure. After six months, they are moved to a growing house for first year animals. Using the techniques described, we have been able to grow a 1.2m animal within one year. The high growth rate and the absence of clinical signs of disease are the evidence used to describe these alligators as normal.

Sixteen alligators from the conservation area of the Everglades were brought to the University of Florida, College of Veterinary Medicine for surgical implantation of radio transmitters to facilitate long term tracking of the animals. All alligators were weighed, measured, and blood was collected. Length of the alligators varied from 189 cm to 282 cm. The weight varied from 18 kg to 79 kg. Nine of the alligators were male and eight were female. The same series of tests were performed on blood collected from the Everglades alligators as had been previously run on the captive normal control alligators. All blood tests were performed by the clinical pathology laboratory at the University of Florida, College of Veterinary Medicine. This laboratory was used to eliminate testing variance that could be encountered by use of different analytical methods. All data from blood samples submitted was analyzed using SAS statistical software. ANOVA was run on the pooled samples from the Everglades, Louisiana, and Conservation area of the Everglades (wild caught) alligators. The Everglades and Louisiana hatchlings had been farm reared and were considered to be clinically healthy animals. Sample sizes for the Everglades and Louisiana hatchlings were 27 and 28 animals, respectively. A Duncan's multiple range test was performed in conjunction with the ANOVA for the pooled samples to determine statistical differences between pooled samples.

Results and Discussion

CBC interpretation from the wild caught alligators showed a significant increase in white blood cell counts and evidence of eosinophilia and basophilia. A lymphocytosis was also noted. Heterophils were significantly decreased in number compared to farm raised alligators. White blood cell counts averaged 55% higher in Conservation area alligators compared to farm raised alligators. Both eosinophils and basophils were approximately 100% higher in ratio to total white cell count in wild alligators compared to farm raised. The lymphocyte ratio was 5% higher than Everglades, and 10% higher than Louisiana alligators. Heterophil ratios averaged nearly 30% less than farm raised alligators. Eosinophilia and concomitant basophilia often occur in parasitic infections or hypersensitivities. Lymphocytosis can occur due to antigenic stimulation and is common in all domestic species, and may occur during chronic stages of infection. Heterophils are analogous to neutrophils in mammals. Neutropenia in mammals is always considered serious and often warrants a guarded to grave prognosis, however, the cause for heteropenia in alligators is unknown, as is the prognosis carried with heteropenia. Band cells that may be immature foms of heterophils were not seen in the blood smears.^12,3,5

Blood smears from all but one of the alligators contained an erythrocyte parasite of the Haemogregarina species. These parasites were numerous in all the slides in which they appeared. This organism has been considered to be commensal and not pathogenic. From the high numbers of organisms seen in the blood films however, it is possible that the organism is causing pathogenic effects on the alligator during times of debilitation from malnutrition, parasitism, intoxication, or other disease. Since all of the alligators were underweight, Haemogregarina organisms may have further debilitated the animals. Serum chemistry of the wild caught Conservation area alligators were marked by a large increase in globulin levels. The albumin level was decreased compared to farm raised alligators. The total protein concentrations for the alligators were slightly elevated in Conservation area alligators, and the increase was small but statistically significant. It appears that there was a shift in protein concentrations from albumin to globulins due to the inflammation process, and albumin production decreased in order to maintain proper blood oncotic pressure in the blood.

Protein electrophoresis had the most dramatic changes seen in the blood from farm raised to wild alligators. Electrophoretic concentrations of albumin for wild caught alligators averaged 0.82 g/dl; while, Everglades farm raised alligators were double that (1.62g/dl). A slight decrease in the region of alpha 1, alpha 2, and beta 1 globulins was noted for wild caught alligators compared to farm raised. The largest changes occurred in the beta 2 and gamma 1 regions of the electrophoretogram. The beta 2 region had concentrations of 0.13 g/dl for farm raised alligators, however, wild caught alligators averaged 1.47 g/dl in the beta 2 region. The gamma 1 region of the electrophoretogram exhibited the same pattern of polyclonal gammopathy. The gamma 2 region was slightly decreased in wild caught alligators compared to farm raised.

Chronic phase proteins, namely beta and gamma immunoglobulins, can cause a marked increase in globulin levels. Polyclonal gammopathies are characterized by a broad based electrophoretic peak, as is seen in the wild caught alligators. These broad based peaks are composed of a heterogeneous mix of immunoglobulins. Polyclonal rises are normally associated with long term antigenic stimulation occurring in chronic inflammatory diseases, immune mediated diseases, and liver diseases. Because all the alligators were collected randomly, it would seem unlikely that immune mediated or liver disease was present in all animals captured. Therefore, chronic disease seems more probable.¹

The alligators from the Conservation area of the Everglades were also underweight and appeared malnourished for their length. Causes for their poor body condition are possibly nutritional related to either insufficient prey numbers and/or unsuitable prey. Sub-clinical disease caused from either bacterial and/or parasitical infection could also be a factor for the poor body condition of the animals. It is likely that combinations of all the factors listed are resulting in the relatively poor body condition the animals appeared to be in. Intoxication may also causing the condition of these wild alligators, but the toxin has yet to be found. No testing has been done to date on wild alligators we have had in our possession. Feces of the Conservation area alligators have not been examined for parasites, although they were quite probably infected with internal parasites.

Conclusions

Baseline data from clinically healthy alligators along with visual examination provided a basis to suspect disease processes were occurring in wild caught alligators from the Everglades. Chronic inflammation and/or infection are present in wild Everglades alligators as evidenced from CBC, serum chemistry, and protein electrophoresis data. The possible causes include parasitism, both gastrointestinal blood, and external parasites, sub-clinical bacterial disease, and malnutrition from lack of prey numbers or unsuitable prey.

References

1.  Duncan, R.J., K.W. Prasse, and E.A. Mahaffey. 1994. Veterinary Laboratory Medicine: Clinical Pathology. Iowa State University Press, Ames, Iowa, Pp. 3 7-62.

2.  Glassman, A-B., T.W. Holbrook, and C.E. Bennett. 1979. Correlation of leech infestation and eosinophilia in alligators. Journal of Parasitology 65 (2):323-324.

3.  Glassman, A-B., C.E. Bennett and T.C. Hazen. 1981. Peripheral blood components in Alligator Mississippians. Transactions of the American Microscopical Society 100(2):210-215.

4.  Khan, R.A., T.M. Forrester, T.M. Goodwin, and C.A. Ross. 1980. A Haemogregarine from the American Alligator (Alligator Mississippians). Journal of Parasitology 66 (2):324-328.

5.  Mateo, M.R., E.D. Roberts, and F.M. Enright. 1984. Morphologic, cytochemical, and functional studies of peripheral blood cells of young healthy American alligators (Alligator Mississippians). American Journal of Veterinary Research 45 (5):1046-1053.