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@ Research > Clinical Research
Clinical Research Projects
The exotic, wildlife and zoological service has an extensive research program which includes conservation/wildlife field projects as well as clinical studies within the College of Veterinary Medicine. Examples of the clinical research projects are outlined below.
Coelomic Endoscopy of the Green Iguana
Endoscopic evaluation of the coelom (body cavity) has been recommended as a safe and important diagnostic procedure in reptiles; however, prior to this study no studies had been undertaken to evaluate endoscopy in any reptilian species. This project evaluated a bilateral coelioscopic technique in green iguanas (Iguana iguana) under general anesthesia using a 2.7 mm telescope system. The levels of difficulty to enter the coelom, insufflate the coelomic cavity, and visualize the viscera were objectively scored by the endoscopists. In addition, the level of difficulty to locate and examine the heart, lung, stomach, small intestine, large intestine, spleen, liver, gall bladder, pancreas, adrenal gland, testis, epididymis, vas deferens, ovary, oviduct, kidney, bladder, and fat body were also objectively scored. Endoscope entry, insufflation, and general coelomic visualization were straightforward. Results indicated that there was no significant difference between left and right visualization scores for lung, liver, pancreas, small intestine, large intestine, ovary, oviduct, testis, epididymis, vas deferens, bladder, fat body, or kidney. However, a left lateral approach to the heart, stomach, and spleen, and a right lateral approach to the gall bladder and adrenal gland were significantly superior (P < 0.05). This project concluded that endoscopy is a safe and effective method for the detailed examination of coelomic viscera in lizards.
[ Hernandez-Divers SJ, Stahl SJ, Hernandez-Divers SM, Read MR, Hanley C, Martinez F and Cooper TL (2004). Coelomic endoscopy of the green iguana (Iguana iguana). J Herpetological Med & Surg, 14:10-18. ]
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Evaluation of Bile Acids in the Green Iguana
The assessment of liver function and disease is difficult in reptiles and therefore this project was initiated to determine whether bile acids could be reliably measured in green iguanas and whether feeding had any affect on their blood levels. Pre-prandial plasma 3a-hydroxy-bile-acids and biochemical profiles were established for a group of healthy male green iguanas (Iguana iguana). The animals were fasted for 48 hours and then fed a herbivorous diet containing 606 +/- 52.6 mg of fat per kg body weight to stimulate bile release. Pre-prandial bile acid levels (7.5 ± 7.8 µmol/L) significantly increased at 3 and 7.5 hours post-prandial to 33.3 ± 22.0 µmol/L and 32.5 ± 8.4 µmol/L respectively. This study demonstrated a significant increase in post-prandial plasma 3a-hydroxy bile acid levels in healthy green iguanas, and therefore fasting status must be considered.
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Comparison of Isoflurane and Sevoflurane following Premedication with Butorphanol in the Green Iguana
Anesthesia remains a difficult and demanding technique in many reptiles. This project was aimed at comparing two different anesthetic gases available in general practice in healthy iguanas. The anesthetic and cardiopulmonary effects of butorphanol followed by sevoflurane or isoflurane were compared in 23 male, green iguanas (Iguana iguana). Heart and respiratory rates were recorded prior to administration of butorphanol (2 mg/kg i.m.) and at 30 min after premedication. Anesthesia was induced in 12 iguanas (Group 1) with isoflurane (5%), and 11 iguanas (Group 2) with sevoflurane (7%). Heart rate, relative arterial oxygen hemoglobin saturation (SpO2), end-tidal CO2 concentrations (EtCO2) were measured every minute for the first 5 min and every 5 min thereafter. Arterial blood gas parameters were determined at 10 and 40 min following induction. Thirty minutes following butorphanol administration, no significant changes in heart and respiratory rate were seen as compared to baseline values. Quality and time to induction were superior with butorphanol-sevoflurane (6 ± 3 min) than with butorphanol-isoflurane (9 ± 4 min). Vaporizer settings during maintenance ranged between 1 - 3% and 2 - 4% respectively. No significant differences in heart rate were noted between groups. In the sevoflurane group SpO2 values were > 90% throughout. Although SpO2 values were < 90% at 20, 25, and 30 min in the isoflurane group, no significant differences in SpO2 values were seen over time and between groups. A significant decrease in end-tidal CO2 concentrations over time was present in both groups, with no significant differences between the groups. At 10 and 40 min, SaO2 values were > 90% in both groups and no significant differences were noted over time and between groups. Recovery time was significantly longer in the butorphanol-isoflurane group (35 ± 27 min) than in the butorphanol-sevoflurane group (7 ± 4 min). The cardiopulmonary effects of butorphanol-isoflurane and butorphanol-sevoflurane assessed in this study are similar and both inhalants appear to be safe and effective for induction and maintenance in the green iguana.
[ Hernandez-Divers SM, Schumacher J, Stahl S and Hernandez-Divers SJ. Comparison of isoflurane and sevoflurane following premedication with butorphanol in the green iguana (Iguana iguana). Journal of Zoo & Wildlife Medicine, accepted August 2004. ]
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Evaluation of Cardiovascular Responses and Blood Gas Determinations in Green Iguanas
In an attempt to help unravel the complexities of reptile anesthesia, we decided to take a step back and investigate some of the critical cardiovascular responses in the green iguana. This project entailed several related studies:
- to investigate the baroreceptor response of green iguanas to atropine, beta-blockers, and alpha-2 agonists,
- to measure and characterize blood gases in conscious green iguanas breathing different concentrations of oxygen, carbon dioxide and nitrogen.
This information will be helpful in improving the safety of general anesthesia in this lizards.
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The Effects of EDTA and Heparin on Hematologic Values of the Green Iguana
Hematology represents an essential component of disease investigation in reptiles. EDTA is typically the anti-coagulant of choice in most animals but in reptiles heparin has been favored due to hemolysis in some species. This study compared the effects of dipotassium EDTA and lithium heparin on hematologic values of green iguanas. Thirty-two privately owned sibling iguanas had blood drawn and the sample was divided into three components: an EDTA tube, a heparin tube, and a non-anticoagulated blood smear. A full reptilian complete blood count was performed on each anticoagulated sample and white blood cell and leukocyte differential counts were performed on the whole blood smears. Heparin and EDTA samples differed significantly in absolute values of thrombocytes, white blood cells, heterophils, and monocytes. The EDTA had no significant effect on the packed cell volume or plasma protein values and the white blood count and differential counts produced with EDTA were more similar to those of the non-anticoagulated blood smear than were the counts produced with heparin. We concluded that contrary to common practice, EDTA is the preferred anticoagulant to use with iguana blood.
[ Hanley CS, Hernandez-Divers SJ, Bush S and Latimer KS (2004). Comparison of the effect dipotassium EDTA and lithium heparin on hematologic values in the green iguana (Iguana iguana). Journal of Zoo & Wildlife Medicine, 35:328-332. ]
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Evaluation of Meloxicam in Green Iguanas
There had not been any pharmacokinetic studies to investigate the use of analgesics in any reptile before this study. Fourteen green iguanas were used to evaluate the single-dose pharmacokinetics of oral and intravenous meloxicam (a commonly available non-steroidal anti-inflammatory drug used in animals). Following fasting for 24 hours and baseline blood collection from the caudal (ventral coccygeal) vein, each iguana was given 0.2 mg/kg of a commercially available oral formulation of meloxicam (Metacam, Merial, Duluth, GA 30069, USA) by stomach gavage. Serial blood samples were collected at 4, 8, 12, 24, 48 and 72 hrs after dosing. Blood was collected into heparin separator tubes, centrifuged, and the harvested plasma samples were frozen at -70°C. Meloxicam levels were determined by high performance liquid chromatography. After a 14 day wash-out period fourteen green iguanas were again blood sampled for baseline levels before being intravenously injected with 0.2 mg/kg of an experimental formulation of meloxicam (5 mg/ml, Merial). Blood samples were collected at 1, 4, 8, 12, 24 and 48 hours after dosing. Blood was collected into heparin separator tubes, centrifuged, and the harvested plasma samples were frozen at -70°C. Meloxicam levels were determined by high performance liquid chromatography. There were no signs of adverse drug reaction and the injectable route provided appropriate levels for 36 hrs. It is hoped that this study will help facilitate the routine use of analgesics for iguanas and other reptiles in discomfort.
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Renal Evaluation in the Green Iguana: Assessment of Plasma Biochemistry, Glomerular Filtration Rate, and Endoscopic Biopsy
Renal disease remains a common problem in reptiles, particularly iguanas. This study was initiated to improve our abilities to diagnose renal disease by formulating a practical method for measuring renal function in the green iguana (Iguana iguana). Plasma biochemistry, iohexol clearance and endoscopic renal evaluation, and biopsy were performed in 23 clinically healthy 2-yr-old green iguanas. Mean (± SD) values for packed cell volume (30 ± 3 %), total protein (62 ± 7 g/L, 6.2 ± 0.7 g/dL), albumin (25 ± 2 g/L, 2.5 ± 0.2 g/dL), globulin (37 ± 6 g/L, 3.7 ± 0.6 g/dL), total calcium (3.0 ± 0.2 mmol/L, 12.0 ± 0.7 mg/dL), ionized calcium (1.38 ± 0.1 mmol/L), phosphorus (1.32 ± 0.28 mmol/L, 4.1 ± 0.9 mg/dL), uric acid (222 ± 100 µmol/L, 3.8 ± 1.7 mg/dL), sodium (148 ± 3 mmol/L or mEq/L), and potassium (2.6 ± 0.4 mmol/L or mEq/L) were considered within normal limits. Values for urea were low (< 1.4 mmol/L, < 4 mg/dL) with 70 % of samples below the detectable analyzer range. Following the i.v. injection of 75 mg/kg iohexol into the caudal (ventral coccygeal or tail) vein, serial blood collections were performed over 32 hr. Iohexol assays by high performance liquid chromatography produced plasma iohexol clearance graphs for each lizard. A three-compartment model was used to fit area-under-the-curve values and obtain the glomerular filtration rate using regression analysis. The mean glomerular filtration rate (± SD) was 16.56 ± 3.90 ml/kg/hr, with a 95% confidence interval of 14.78 - 18.34 ml/kg/hr. Bilateral endoscopic renal evaluation and biopsy provided tissue samples of excellent diagnostic quality, that correlated with tissue harvested at necropsy and evaluated histologically. None of the 23 animals demonstrated any adverse effects of iohexol clearance or endoscopy. Recommended diagnostics for the evaluation of renal function and disease in the green iguana include plasma biochemical profiles, iohexol clearance, endoscopic examination, and renal biopsy.
[ Hernandez-Divers SJ, Stahl SJ, Stedman NL, Hernandez-Divers SM, Schumacher J, Hanley CS, Wilson GH, Vidyashankar AN, Zhao Y and Rumbeiha WK. Renal Evaluation in the green iguana (Iguana iguana): Assessment of plasma biochemistry, glomerular filtration rate, and endoscopic biopsy. Journal of Zoo & Wildlife Medicine, accepted August 2004. ]
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Evaluation of Anthelmintics for the treatment of Pinworms in Radiated Tortoises (Geochelone radiata)
Before this study there had been no evaluation of routine de-worming medications in any reptile species. Twenty radiated tortoises with natural pinworms infections were subjectively and objectively evaluated using fecal flotation and McMaster methods. Oxfendazole and pyrental were trialed, but greatest success was achieved using oral oxfendzole at a dose of 66 mg/kg.
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Avian Minimally-Invasive Surgery: Development of Endosurgical Techniques including Castration and Salpingohysterectomy
Rigid endoscopy is most commonly used for diagnostic purposes in birds, and in particular internal visualization and biopsy. As a result most endoscopic systems utilize a rigid telescope housed within a sheath, through which basic instruments can be inserted into the field of view. This technique has been extremely effective for visualization and biopsy but is severely limited in its ability to facilitate surgery where the triangulation of multiple instruments is required. The advent of human pediatric laparoscopy equipment has opened the door to true multiple-entry endosurgery in small exotic species, including birds. This project pioneered the use of human pediatric laparoscopy equipment in birds and has been used to successfully sterilize male and female pigeons and parrots.
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The Effects of Pre-pubertal Gonadectomy on Adult Health and Behavior of Umbrella Cockatoos (Cacatua alba)
There are many avian behaviors that may result in owner dissatisfaction or relinquishment, including aggression, inappropriate vocalizations, self-injurious behaviors such as feather picking and self-mutilation, and sexual behaviors such as masturbation and regurgitation. Previous individual case experience shows that these behaviors may be mitigated or alleviated through neutering. In addition, avian reproductive diseases are a common problem and may be life threatening. The goal of this project is to determine if neutering cockatoos prior to puberty would have an effect on behavior and health, reducing the number of hormonally-related behavioral and medical problems in these companion animals. Performing these spays or castrations endoscopically also opens up a new area of minimally invasive surgery in birds.
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Chemical Castration of Domestic Pigeons via Endoscopic Intratesticular Injection of Zinc Gluconate Neutralized by Arginine
Recently the FDA approved an injectable sterilant for puppies marketed under the trade name Neutersol ® (Addison laboratories www.addisonlabs.com/Products.htm). This chemical sterilant is zinc gluconate neutralized by arginine and has been shown to atrophy the testes and prostate and render the dog permanently and irreversibly sterile in 99.6% of dogs according to the index study with this drug. This purpose of our study was to evaluate the clinical safety and efficacy of a single intratesticular injection of Neutersol ® in causing sterility/infertility and the effects on testosterone levels in one avian species, domestic pigeons. It is the eventual goal of this line of research to develop a safe, effective, and convenient method of castration for avian species so that birds kept as companion animals will be less likely to develop the behaviors that result in a fracture of the human-animal bond and related medical problems.
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Radiation Tolerance Doses of Cutaneous and Mucosal Tissues in Psittacine Birds Using Colbalt-60 Teletherapy
An understanding of the tolerance of normal tissues included in the treatment field is essential in radiation treatment planning for any animal. Dose response, influence of fractionation, and normal tissue injury have been evaluated extensively in many companion animals. However, there have been no controlled studies of external beam radiation therapy in any avian species. Currently used dosages for external beam megavoltage radiation therapy in birds have been extrapolated from mammalian patients and often appear to provide inadequate doses of radiation for effective tumor control. Thus the goal of this study was to determine the tolerance doses of cutaneous and mucosal tissues of normal birds to provide more effective treatment for tumors that have been shown to be radiation responsive in other species. Ingluvial mucosae and the skin over the ingluvies of nine Psittacine birds were irradiated in 4 Gy fractions to a total dose of either 48, 60, or 72 Gy using an isocentric Cobalt-60 teletherapy unit. Minimal radiation-induced epidermal changes were present in the high dose group histologically. Neither dose-related acute nor chronic radiation effects could be detected grossly in cutaneous or mucosal tissue over a year period.
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Pharmacokinetics and Bioavailability of Meloxicam in Ring-necked Parakeets (Psittacula Krameri)
Reduction of pain and inflammation is an important part of medical and surgical management of avian patients. However, information on the pharmacokinetics and pharmacodynamics of anti-inflammatory drugs in psittacine birds, the most common companion birds, is relatively scarce. Meloxicam preferentially inhibits COX-2, making renal and gastrointestinal side effects less common. This study evaluated the pharmacokinetics of meloxicam given to ring-necked parakeets (Psittacula krameri) orally and intravenously at a dose of 0.5 mg/kg. The elimination half-life was 15 hours after oral administration and 4 hours after intravenous administration. Peak serum concentrations were 1.38 ug/ml and 3.86 ug/ml after oral and intravenous administration respectively. The results suggest that meloxicam should be administered at 0.5 mg/kg every twice daily orally or every 4 hours intravenously.
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Comparison of Three Methods of Long Bone Fracture Repair in Rabbits
Rabbit bones are delicate in comparison to that of other domestic companion animals. For example, the skeleton of a rabbit represents only 7-8% of body weight but is 12-13% of body weight in a cat. Therefore, rabbit long bone fractures are a common problem and the application of inappropriate surgical implants can lead to repair failure. So, the purpose of this study is to compare three methods of routine surgical repair:
- plate applied to the lateral surface;
- interlocking nail;
- IM pin with a tie in to a type 1 external skeletal fixator.
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