Abstract

Construction of a building designed to temporarily house chimpanzees (Pan troglodytes) facilitated health assessments, and medical and dental interventions in an established group of 33 chimpanzees. The chimpanzees lived in a completely outdoor South Florida habitat. Little medical information on these animals was previously available due to challenges involved in immobilizing, treating, and reintroducing chimpanzees in this environment. This report describes strategies to introduce and habituate the chimpanzees to the facility and will also describe procedures including physical exams and vasectomies. Viral survey results and histopathologic findings will be presented.

Introduction

The chimpanzee colony at Lion Country Safari was established in the early 1970s when chimpanzees were brought to this zoological park from diverse sources including U.S. medical research laboratories. Breeding continued within the colony through 2002. This colony is one of the largest groups of chimpanzees among American Zoological Association accredited zoos. This group includes some of the oldest chimpanzees in the U.S., animals of African origin, and young offspring. Behavioral and scientific data from these animals have been and continue to be shared with a number of research groups exploring questions of chimpanzee aging, ethology, evolution, genetics, health, husbandry, and pathology.

Methods

For several years, the chimpanzees have been divided into subgroups within the outdoor exhibit to promote compatible social grouping. Established subgrouping was maintained as much as possible before, during, and after anesthetic procedures. Planning the composition of any temporary social groups within the facility was important to encourage voluntary transfer of animals into the building and to help prevent intraspecific aggression between individuals when chimpanzees were reunited.

Four months before any anesthetic procedures, chimpanzees were encouraged to transfer into the facility as a subgroup with food rewards. The subgroup would interact with keepers throughout the day within the facility, spend the night there, and then return to the outdoor exhibit.

Adult animals expected to become highly excitable during immobilization procedures were given crushed diazepam (Diazepam, Abbott Laboratories, North Chicago, IL, USA; 0.2 mg/kg PO) in a small amount of fruit drink the previous afternoon and the morning of anesthesia. In general, this preanesthetic oral sedation was avoided to reduce the likelihood of vomiting and aspiration. Pre-darting stress was usually minimal when the animal was separated from other chimpanzees the day before and darted in the morning. Separated animals could still see and hear other chimpanzees in the facility and in the nearby exhibit. Darting was facilitated by having a staff member distract the chimpanzee from one end of the enclosure while the dart was fired from behind the animal.

A combination of ketamine (Ketaset, Fort Dodge Animal Health, Fort Dodge, IA, USA; 10–15 mg/kg IM) and xylazine (Xylazine, Phoenix Scientific, Inc., St. Joseph, MO, USA; 0.1–0.2 mg/kg IM) proved most reliable for immobilization. Telazol (Telazol, Fort Dodge Animal Health, Fort Dodge, IA, USA; 4.0 mg/kg) and xylazine (0.6 mg/kg) failed to produce satisfactory sedation in one chimp. In assessing more than 25 immobilizations, it appeared that ketamine dosed at 10–15 mg/kg with xylazine at 0.2 mg/kg afforded the most efficient and complete immobilizations with less need for supplemental drugs. When additional supplementation was needed to reduce any movement, midazolam (Midazolam HCl, Bedford Laboratories, Bedford, OH, USA; 0.2 mg/kg IM) or ketamine (1–4 mg/kg IM) was effective. During induction, chimpanzees usually moved to a sitting position on the ground. Chimpanzees sometimes leaned forward, hyperflexing their necks. This was of concern as it potentiated upper airway obstruction; therefore, neck posture and tongue position were closely monitored. Once immobilized, chimps were strapped into a stretcher which assisted in control of any arm or hand movement.

Chimpanzees were placed in dorsal recumbency, intubated, and placed on isoflurane if procedures required more than 30 min of anesthetic time. Use of a long laryngoscope blade (Miller #4, Henry Schein, Inc. Melville, NY, USA) facilitated efficient intubation.

Procedures performed on anesthetized animals included physical examinations, blood collection, intradermal tuberculin testing, electrocardiographic studies, punch biopsies for genetic analysis, chest radiographs, and collection of feces for culture and parasitology. Blood was typically collected from the distal radial vein using a butterfly system that incorporates a vacutainer (Vacutainer Brand Safety-Lok Blood Collection Set, Becton Dickinson and Company, Franklin Lakes, NJ, USA). The blood samples were then utilized to perform complete blood counts, serum biochemistry analyses and various types of serology.

Vasectomy

Six chimpanzees were vasectomized. Once anesthetized, these animals were maintained in dorsal recumbency. Towels were placed under the testicles to support their weight and to decrease tendency for dependent edema associated with surgery. Separate longitudinal prescrotal incisions were made on each side of the penis over each spermatic cord. Blunt dissection to the level of tunic was made, the tunic was sharply incised, and each vas deferens was clamped at two sites approximately 4 cm apart in its mid-section. A ligature of 2-0 polydioxanone (PDS, Ethicon, Inc., Somerville, NJ, USA) was placed proximal to each clamp and the section of vas deferens between the ligatures was excised. The open tunic was flushed with chlorhexidine (Chlorhexidine Solution, The Butler Company, Columbus, OH, USA) and a mixture of amikacin in 0.9% saline (Amiglyde-V, Fort Dodge Animal Health, Fort Dodge, IA, USA). The tunic and subcutaneous layers were sutured separately in simple interrupted fashion and a continuous subcuticular pattern was used to close the skin, with 2-0 PDS. A small amount of tissue adhesive (Nexaband Liquid, Abbott Laboratories, North Chicago, IL, USA) was used over skin sutures in some cases. Antibiotic coverage included cefazolin (Cefazolin, Geneva Pharmaceuticals, Inc., Dayton, NJ, USA; 25 mg/kg IM or SC) intraoperatively and chewable amoxicillin/clavulanate (Augmentin, GlaxoSmithKline, Research Triangle Park, NC, USA; 10 mg/kg PO, BID for 5 days) postoperatively. Flunixin meglumine (Flunixamine, Fort Dodge Animal Health, Fort Dodge, IA, USA; 1 mg/kg IM) was administered for analgesia prior to recovery.

Dental Procedures

Three, 30–55 yr-old, chimpanzees were transported to a veterinary dental clinic for complete dental radiography, evaluation, and treatment. Chronic fractures of the incisors and canines with periapical lesions were the most common abnormalities. A male that presented for a facial fistula was found to have an endodontically involved canine root fragment requiring lateral alveolar plate removal to access. Diseased incisors and canines were extracted and gingival flaps were performed. Osseoconductive synthetic bone graft material (Consil, Nutramax Laboratories, Inc., Edgewood, MD, USA) was used to fill the extraction defects. Closure was achieved with simple interrupted sutures of 4-0 chromic gut (Ethicon, Inc., Somerville, NJ, USA). Animals were maintained under gas anesthesia for 1–4 h to perform the tooth extractions.

Chimpanzees undergoing invasive dental procedures received ceftiofur (Naxcel, Pharmacia & Upjohn Company, Kalamazoo, MI, USA; 2.2 mg/kg IM) intraoperatively. Crushed chewable amoxicillin/clavulanic acid (9–11 mg/kg PO, BID x 5 days) and acetaminophen suspension (Tylenol, McNeil Consumer and Specialty Pharmaceuticals, Fort Washington, PA, USA; 9 mg/kg PO, BID x 3 days) were administered. The animals consumed the medications best when they were placed on soft fruits such as oranges or mixed with fruit drinks.

Respiratory Disease

In July of 2003, a virulent respiratory disease swept through the entire colony, most severely affecting a subgroup of 18 individuals. This subgroup was brought into the facility for observation and treatment. The most severely affected individuals showed increased inspiratory effort, purulent nasal discharge, open-mouth breathing, and decreased appetite. Infant and juvenile animals and their dams were only minimally affected. Immobilizations were not performed on animals due to the increased anesthetic risk in animals with respiratory disease. Instead, severely affected animals were treated empirically by darting with ceftiofur (2–3 mg/kg IM, SID x 5 days) followed by an oral regimen of amoxicillin/clavulanate (10 mg/kg PO, BID x 7 days). All chimpanzees fully recovered in approximately 14 days.

Results and Discussion

All chimpanzees, with the exception of an individual suffering from cerebrovascular insult, were clinically normal at the time of serologic sampling. A small number of seropositive tests for Hepatitis A (2 of 7) and Hepatitis B (1 of 9) occurred in some of the older animals; these chimpanzees were former laboratory animals believed to have been used in hepatitis research. Eight chimpanzees tested for Hepatitis C were negative. No hematologic or serum chemistry abnormalities compatible with hepatic illness were noted. All chimpanzees including those of wild origin were negative for human immunodeficiency virus, human T-lymphotrophic virus, simian immunodeficiency virus, and simian T-lymphotrophic virus.

For other viruses, the number of positive animals/number of animals tested were as follows: Influenza A (8/17), Influenza B (0/17), Parainfluenza I (2/7), Parainfluenza II (0/17). Parainfluenza III (11/17), Measles (0/17), Respiratory Syncytial Virus (0/17), Simian A-8 (0/17), Herpes simplex I (16/18), Herpes simplex II (0/17), Human Varicella (11/17), Chimp Cytomegalovirus (17/18), Epstein Barr Virus (18/18), Simian Foamy Virus (5/6). As most tested animals were seronegative for Parainfluenza III prior to the respiratory outbreak of July 2003, and several were seropositive after that time, it is postulated that this virus contributed to clinical disease expressed that summer. Several animals were seropositive for West Nile virus and/or St. Louis encephalitis virus.

Seventeen chimpanzees were given intradermal tuberculin tests (Tuberculin Mammalian, Human Isolates Intradermic, Synbiotics Corporation, San Diego, CA, USA) and were negative. Nine of these chimpanzees also had blood tuberculosis tests for Mycobacterium tuberculosis complex that were negative. (Primagam, BioCore Animal Health, Omaha, NE, USA).

A 38-yr-old, male chimpanzee had acute, left-sided hemiparesis and depression. A diagnosis of cerebral infarction was made via CAT scan. The animal had normal radiographic, electrocardiographic, and cardiac ultrasound findings during this illness. It further declined and expired 5 days after presentation. Severe myocardial fibrosis was seen on histopathology. An approximately 40-yr-old female chimpanzee also succumbed to cardiac disease characterized by myocardial fibrosis. Because fatal cardiac fibrosis has been associated with vitamin E deficiency in primates, analysis for liver concentration of alpha-tocopherol was performed.^3,4 Hepatic levels of vitamin E were approximately 24 µg/g in the male and 2.3 µg/g in the female. Expected liver vitamin E level in human adults is 20 µg/g (E. Dierenfeld, personal communication) It has been postulated that depressed vitamin E levels may lead to myocardial fibrosis that is not reversed by subsequent vitamin supplementation.⁴ The lifetime dietary history of these two chimpanzees was not known. It has also been theorized that viral infections may contribute to myocardial fibrosis.^1,2 The viral survey performed in this colony lends insight into the identities of viruses that may contribute to cardiac disease.

No anesthetic-related mortalities occurred. One chimpanzee had brief, severe hypoxia from upper airway obstruction due to hyperflexion of the neck soon after being darted. Vomiting occurred in three individuals in the postoperative (vasectomy) period. These three chimpanzees were among the first immobilized and had received a small amount of diazepam in juice within 2 h prior to darting, a practice which was discontinued as anesthetic dosages were refined. Vomiting could also have been caused by abnormal gastrointestinal motility as a result of gas anesthesia or the use of xylazine.

All vasectomized chimpanzees recovered from surgery without significant complications. Two animals had scrotal swelling that was most apparent several days postoperatively. This complication occurred despite intraoperative attempts to support the weight of the scrotum and to provide gentle tissue handling. These chimpanzees were monitored daily. Although use of anti-inflammatories was considered, the postoperative inflammation resolved on its own. One animal had a mild incision line infection that was successfully treated with minor debridement and oral antibiotics.

No complications from dental procedures were observed. All chimpanzees were awake and ambulatory within 4 h post-extubation and all consumed juice and/or fruit in the immediate postoperative period. Outward manifestations of oral pain were not apparent in any chimp. The male that underwent removal of a retained canine fragment and a female that underwent incisor and canine extraction exhibited substantially brighter behavior following the procedure. Although these chimps had not been known to have difficulty chewing or drinking prior to or after the procedure, keepers noted them to be more energetic and vocal following the extractions. Keepers described the male as a “new chimp.”

Acknowledgments

Special thanks to Drs. Pat Frost, Steve Bolin, Jim Oosterhuis, and David Fagan for several telephone consultations. Thanks also to Wildlife Director Terry Wolf, chimpanzee keepers Kelly Greer, Andrew Halloran, and Michele Schwartz for their tireless efforts with this unique group of animals. The support of Lion Country Safari veterinary technicians and curators is greatly appreciated.

Literature Cited

1.  Cotran, R.S., V. Kumar, and S.L. Robbins. 1994. The heart. In: Schoen, F.J. (ed.). Robbins Pathologic Basis of Disease. 5th ed. W. B. Saunders Co., Philadelphia, Pennsylvania. Pp. 517–582.

2.  Craighead, J.E., S.A. Huber, and S. Siram. 1990. Animal models of picornavirus-induced autoimmune disease: their possible relevance to human disease. Lab. Invest. 63:432–446.

3.  Liu, S., E.P. Dolensek, J.P. Tappe, J. Stover, and C.R. Adams. 1984. Cardiomyopathy associated with vitamin E deficiency in seven gelada baboons. J. Am. Vet. Med. Assoc. 185:1347–1350.

4.  McNamara, T., E.P. Dolensek, S. Liu, and E.D. Dierenfeld. 1987. Cardiomyopathy associated with vitamin E deficiency in two mountain lowland gorillas. Proc. Int. Conf. Zool. Avian Med. 1:493.