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Chimp VAG Annual Report 2006

SSP/TAG:  Common Chimpanzee  DATE:  19 September 2006 


Kathryn C. Gamble DVM, MS, DACZM Kay Backues, DVM, DACZM

Lincoln Park Zoo    Tulsa Zoo and Living Museum

Director of Veterinary Services  Head Veterinarian

2001 North Clark Street   5701 E 36th Street North

Chicago, IL 60614    Tulsa, OK 74115

Ph:  312.742.7722    Ph:  918.669.6243

Fx:  312.742.7823    Fx:  918.669.6260 

MORBIDITY (Significant illnesses/issues facing this species this year):

-     Considering the mortality profile of over 50% of adult deaths cardiac-related, it should not be surprising that congestive heart failure and cardiac disease remain the most routine consultations.  This concern was addressed in the Standard of Care: Veterinary Guidelines generated by the veterinary advisors in concert with the SSP steering committee (attached).

-     Extensive consultation by veterinary advisors and collaborative institution to address a geriatric animal housed singly which had not been examined in nearly 20 years.  Through extensive negotiation, a thorough physical was conducted including tracheal lavage, viral titres, and cardiac assessment.  Although the chimpanzee was quite healthy considering the advanced age, rational consideration was made to his health management of chronic steroid administration to address unknown rectal bleeding and identified atypical mycobacterial pneumonia and underlying positive viral serology that will be problematic for managing social situations for this animal.

-     Treatment for adult female chimpanzee with presumed cerebral stroke is currently ongoing.

-      Current consultation from veterinary advisor on an active coccidiomycosis case at a different institution than that requesting guidance last year and veterinary care at a laboratory facility. 

MORTALITY (Causes of death in this year):

      Neonates Stillbirths   0.0.0

            Conspecific trauma  0.0.2

                Metabolic bone disease 0.1.0

      Adults  Neoplasia    0.1.0 (37 yr)

            Exhibit-related   1.0.0

            Infection    1.1.0 (13, 18 , 33 yr)

            Cardiac causes

              Infarction   0.0.0 ( yr)

              Arteriosclerosis 1.0.0 (49 yr)

              Cardiac disease 4.0.0 (26, 28, 35, 41 yr – stress


          Total     7.3.2 

BIRTHS:  0.0.2 offspring – died from conspecific trauma; 0.0.2 offspring with one dam-reared, one surrogate-reared 

ANESTHESTIC PROTCOLS excerpt from Standard of Care SSP guidelines

Anesthesia:  Induction of anesthesia is routinely accomplished by intramuscular injection of a sedative(s) following an appropriate (12-24 hour) fasting interval.  In a 2006 survey of attending veterinarians in AZA-accredited institutions holding chimpanzees (n=40), 80% responded to queries about induction regimens, supplementation, adjustment of protocols for known cardiac patients, intubation frequency, reversibility of anesthetic protocols, and changes in protocols over the last decade. 

Table 1.  Typical immobilization agents included Telazol® (tiletamine-zolazepam), ketamine, or combination of these products with medetomidine.  Occasionally, xylazine, benzodiazepenes (diazepam or midazolam), or butorphanol were utilized in the combinations or as premedications.  Very rarely carfentanil was included. 

    Drug/drug combination Dose Frequency utilized*
    Telazol® alone 1.5-3 mg/kg 15 %
      3-6 mg/kg 34%
    Ketamine alone 2-5 mg/kg 9%
      8-10 mg/kg 9%
    Telazol®//ketamine 1-3 mg/kg// 1-3 mg/kg 3%
    Telazol®//medetomidine 2 mg/kg// 0.02-0.030 mg/kg 9%
    Ketamine//medetomidine 2 mg/kg// 0.015-0.025 mg/kg 9%
      2-5 mg/kg// 0.03-0.04 mg/kg 13%
      5-7 mg/kg/ /0.025-0.07 mg/kg 25%
    Ketamine//midazolam 4-5 mg/kg// 0.05-0.1 mg/kg 3%
    Medetomidine/butorphanol/midazolam 0.015mg/kg// 0.085mg/kg//  0.06 mg/kg 3%
    Medtomidine/butorphanol/ketamine 0.015 mg/kg// 0.15-0.3 mg/kg// 1.5mg/kg 3%

*Of the 33 responding veterinarians, this is the percentage of veterinarians using this regimen.  In some instances, veterinarians provided two or more routine induction protocols. 

Table 2.  Typical supplementation agents included Telazol® (tiletamine-zolazepam) or ketamine intramuscularly (at higher doses) or intravenously (at lower doses).  Inhalant anesthetic agents, primarily isoflurane, were used to effect when this was routinely planned for the procedure.  Occasionally, propofol (1-2 mg/kg, i.v., n=1, 3%) or diazepam or midazolam (0.1 mg/kg i.m., n=1, 3%) were utilized to maintain the induction.   

Drug Dose Frequency utilized**
Telazol® alone 1-2 mg/kg   6%
Ketamine alone 1-2 mg/kg 50%
  3-4 mg/kg 13%

** Of the 33 responding veterinarians, this is the percentage of veterinarians using this regimen. 

Maintenance of the anesthetic event will be determined by the extent of the procedure and can be accomplished by supplemental parenteral agents or inhalant methods.  However, it is strongly encouraged that for procedures longer than 30 minutes (i.e., most standard physical examinations) chimpanzees be intubated and maintained by inhalant agents such as isoflurane or sevoflurane in oxygen.   In the survey, 48% of the 33 veterinarians responding routinely intubate all anesthetized chimpanzees, 19% routinely intubate at least 50% of the time, while 25% do not routinely intubate any of their chimpanzees. 

Revision of the induction protocol should be considered for animals with cardiac disease or risk factors for cardiac disease – i.e., obesity, advanced age (30 yr or greater), or undocumented cardiac health in these older adults.  In the survey, only 17 veterinarians have managed – or are managing - active cardiac disease in chimpanzees.  Of these, 6 (35%) did not alter their primary induction method, as they were using ketamine or Telazol® exclusively at the lowest dose possible to safely induce the animal.   Eleven of the remaining veterinarians, 5 indicated that the primary induction regimen changed to ketamine alone, 2 avoided alpha-2 agonists (i.e., xylazine or medetomidine), and 1 changed to Telazol® alone.  Three of the veterinarians reported discontinuing elective sedations in known cardiac disease patients. 

Intra-procedural monitoring of heart rate and rhythm, pulse quality, capillary refill time (CRT), respiration depth and rate, and body temperature is the minimal assessment necessary during an anesthetic event.  Close monitoring should be ongoing regularly throughout the procedure.  During protracted procedures, veterinarians are encouraged to add EKG, pulse oximetry, and blood gases as monitoring tools.   Although re-positioning will occur due to the procedure needs, lateral recumbency typically provides improved anesthetic maintenance. 

During recovery, chimpanzees should be positioned to minimize risk of aspiration if regurgitation, vomition, or heavy salivation occurs.  It may be helpful to maintain this position with hay or blankets placed along the animal’s dorsum with the head slightly elevated but the mouth directed downwards.  The torso can be placed in lateral or sternal recumbency with these directions.  Medetomidine induction can be reversed intra-procedurally or at the conclusion of the procedure with i.m. atipamezole at 5 mg of atipamezole for each 1 mg of medetomidine utilized.  All but one institution using medetomidine reversed the sedation in this manner.  Institutions using xylazine utilized yohimbine (0.13mg/kg) i.m. to reverse the sedation.  Where butorphanol or midazolam were utilized, occasionally it was reported that naloxone (Narcan®) or flumazenil were used for reversal. 

Over the last decade, changes were reported in anesthetic protocols in 40% of the responding institutions.  These changes largely focused on increased use of medetomidine and reduced use of Telazol®.  Despite this, 19% of the responding veterinarians reported mixed results, rousable inductions, or reduced confidence in medetomidine regimens. 

VACCINE RECOMMENDATIONS excerpt from Standard of Care SSP guidelines

Immunization:  Vaccinations should be considered for each animal and troop by collection history, risk of exposure, and current human prophylaxis guidelines.  Pediatricians and infectious disease specialists can serve as both a reference and possibly a source of these products.  Separate protocols for juveniles and adults should be developed and maintained.  Vaccinations that should be considered minimally include measles, polio, and tetanus.  Hand-raised infants may require additional vaccinations as compared to mother-reared infants due to increased direct exposure to human caregivers.  Chimpanzees with routine exposure to free-ranging mammalian wildlife should be considered for extra-label rabies prophylaxis. 

Whenever possible, killed or subunit vaccine products should be utilized rather than modified-live (MLV) products for vaccinating chimpanzees. This choice will minimize adverse vaccination events, particularly those due to re-activation of disease agents.  It is particularly important to note that neither efficacy nor safety has been confirmed formally for these vaccination products in chimpanzees, or any great ape species, so are used in an extra-label manner.  However, with the extensive administrations that have occurred in AZA institutions to date, no particular species sensitivities have been identified.  However, it is recommended to heed warnings that accompany human guidelines, such as not administering rubella vaccinations to pregnant or non-contracepted, reproductively active females. 

Additionally, influenza vaccination should be considered based on troop history, exhibit construction, visitor proximity, and current status of influenza in the human population. 

CONTRACEPTION excerpt from Standard of Care SSP guidelines 

To control reproduction, basic anatomy and physiology must be understood for this species so that the optimal approach is selected.   In female chimpanzees, the normal (menstrual) cycle is 36 days with a 72 hours menses.  Grossly visible blood in the urine is inconsistently observed although hematuria can be detected by reagent strips and may be used to track individual females.   Sexually mature female chimpanzees also develop marked swelling of the perianal and perineal tissues due to interstitial fluid accumulation that fluctuates with hormonal influences.  This genital swelling (intumesence) increases to peak size and turgidity during the follicular phase of the cycle.  Lutenizing hormone (LH) increases and causes ovulation to occur during the last 24-28 hours of maximal swelling.  The luteal phase, following ovulation, is characterized by reduction of swelling as the estrogen concentrations decline and progesterone concentrations rise.    

Perineal intumesence is a distinct visual marker of receptivity and potential fertility with marked impact on sociosexual behavior.  During peak swelling, females demonstrate more assertive behavior.  Troop males of all ranks interact preferentially with intumescent females and their offspring. Competition between males, concurrent with agonistic behaviors, will occur with increased frequency in the presence of cycling females.  It is has been documented that mother-raised infants benefit from the presence of cycling females in a troop and have improved adult social and sexual competence. 

Because of the profound effects on the normal sociosexual behavior of chimpanzees, genital swelling should not be completely eliminated by the contraceptive option elected.    In considering contraceptive options, both genders must be evaluated to permit prevention of pregnancy while minimizing impact on troop behavior.  It is important to consider reversibility and safety of these options as well as the tendency of weight gain seen with the hormonal methods of contraception. 

Female contraception:  Oral contraceptives ("birth control pills”) are the same products utilized for human females with a combination of progesterone and estrogens.  It is important to note that the human menstrual cycle is shorter at 28 days but the standard to higher-dose products can be prescribed successfully for chimpanzees at this dose frequency.   These medications act by negative feedback on the hypothalamus with ultimate suppression of the LH surge and follicular stimulating hormone (FSH) activity.  The progesterone component has other effects on the reproductive tract (see below) that improves the contraceptive ability of the product.  The majority (58%) of the reversible contraceptive bouts reported to the Contraceptive Advisory Group (CAG) for chimpanzees are by this method.  Oral contraceptives are reported with a < 4% failure rate in chimpanzees but it is unclear if this is failure of the product or non-compliance of the chimpanzee; in humans, missed doses are essentially the cause of contraceptive failure with these products.    In addition to good contraception, these products are rapidly cleared by the body following discontinuation so are rapidly reversible.  In some cases, minimal to moderate impact on the cyclic intumesence is seen in females on this method of contraception with various degrees of swelling and breeding behavior possible. 

It is critical that the female receive this product daily, consistently at the same time of day, and completely without refusal for optimal pregnancy prevention.  Chimpanzees can be experts at secreting pills offered so complete consumption must be assured and the training maintained by utilizing the package placebos.  When a pill is missed, a second dose should be administered promptly and if one day is entirely missed, two doses should be offered within 24 hours to maintain efficacy.  A side effect of administration of many antibiotics, particularly by the oral route, is reduced efficacy of oral contraceptives due to changes in drug metabolism.

Parenteral progesterone analogues (MGA implants, Norplants®, intramuscular Depo-provera®) share the same contraceptive mechanism of interference with fertilization by thickening cervical mucus, interrupting gamete transport, and disruption of implantation.  It is important to note that ovulation and cycling do occur on these products, even with successful contraception.  The CAG database maintains that 29% of the female chimpanzees have utilized a solid silastic implant (melengestrol acetate, MGA) with a 4% failure rate.  It is unclear what portion of these failures is loss of the product or failure of the drug.  Norplant® (levogestrol) is no longer utilized in human medicine due to repeated failures as the product approaches the end of its five year cycle.  Although these products are good contraceptives and do not require daily medication events, a surgical procedure is required to place some of these products, except the depo-provera injection.  Implants must be routinely checked to be in place by palpation during training or scanning a transponder microchip placed within the implant.  Unlike the oral contraceptives, the parenteral progesterones tend to gradually eliminate perineal intumescence with accompanying negative social side effects although the return of visible cycling can be used as a marker of reduced contraceptive efficacy.        

With Depo-Provera® administration, repeated administration is required every three months.  With implants, implant preparation is required before surgical intramuscular placement of the device.  A window of two weeks is required to gas sterilize (EtO) and aerate the implant before utilizing it.  Following this, the implant is placed but not considered fully effective for four weeks.    The surgical site must be fully healed before contraception is assumed.  The failure rate of the MGA implant is 25% in chimpanzees. 

Mechanical contraception (intrauterine devices or IUDs) causes irritation to the endometrium to prevent implantation of an embryo.  Surgery is required to place these devices and the retrieval threads must be cut short to prevent voluntary removal.  Higher contraception failures are reported with IUD use, including spontaneous expulsion of the devices, particularly from young, nulliparous animals. 

Permanent contraception can be accomplished by ovariohysterectomy (OHE) or tubal ligation.   OHE should be considered in only those females with reproductive tract lesions.   The chimpanzee pelvic canal is very deep and splitting the pelvic symphysis may be required to fully access the uterus during an OHE.  In situations where uterine fibromas (leiomyomas) are present, complete removal of the ovaries is necessary to prevent recurrence with potential fatal consequences.   

Male contraception:  These contraceptive efforts have the advantages of minimizing impact on the troops’ cycling females, including preventing their weight gains.  Male contraception is a consideration for multi-male breeding troops to permit selection of paternity. 

Permanent/semi-permanent contraception can be accomplished through vasectomy that simply severs the vas deferens to prevent sperm passage from the testes to the penile urethra.  As this is not castration, hormonal profiles remain intact so the male’s libido and sexual interactions should remain typical.   Castration should only be considered in situations of genitourinary tract disease.  With appropriate surgical technique, the deliberate reversibility of the technique can be improved while preventing spontaneous recanalization and return to fertility. 

Although this procedure requires immobilization and surgery, it is routine in approach.  In contrast to the human male, the chimpanzee vasectomy must be approached inguinally or along the spermatic cord rather than along the scrotum.  The vas deferens is isolated then transected.  When permanent contraception is desired, suture ligation should be placed before transaction that permits removal of substantial (1.5-2cm) portions of the vas or, in new techniques that seem more successful at preventing recanalization, a light cautery is applied to the mucosa of the cranial (distal) vas segment, by placing a thin cautery needle into the lumen that preserves the muscular tunic. This intact but sealed segment of vas prevents recanulization of the vas and return to fertility in humans, whereas ligating each segment has led to necrosis of the vas with recanalization.  For potentially reversible vasectomies, the caudal (proximal) segment of the vas is not cauterized to allow sperm to escape into the vaginal tunic, creating a sperm granuloma.  In humans, this method has prevented excessive pressure from sperm blockage in the epididymis that would otherwise damage the delicate tissues of the epididymis and permanently negatively impact sperm production. 

Vas plugs of silastic material have only been used in a few animals with inconsistent results.  Concerns of permanent sterility even following removal or failure to block transfer of viable sperm to the urethra have both been encountered.    

Both genders may be contracepted with gonadotropin releasing hormone (GNRH) analogues (deslorelin and leuprolide).  These products act by over-stimulating then suppressing FSH and LH from the anterior pituitary gland through negative feedback.  It is important to note that the initial effect of these products is increased fertility so adequate contraception must be overlaid while the GNRH analogue reaches maximal effects.  Ultimately due to GNRH analogues, contraception occurs with a subsequent decrease in testosterone and sperm production for males that is expected with a concurrent reduction in aggression.  This may be another use of these products in troop management.  Decrease in estrogen and progesterone with ovulation suppression is expected in the female.  However, GNRH analogues are not widely in use at this time.  Success and failure rate has not been determined yet for chimps nor is the impact on normal sociosexual behavior known.  Further research is warranted for the use of this contraceptive in chimpanzees of both sexes.


Great Ape Blood-typing (Gamble, Moyse):  Common chimpanzee blood types are under review with the other three great ape species in a multi-year (2006-2009) project based at Lincoln Park Zoo.  Table-top human techniques are being utilized and validated to improve clinical responses in transfusion situations and consider evolutionary biology in comparison to human and other ape species blood types. 

Development of a cardiac disease formulary (Backues, Gamble):  Based on recent experiences and drug uses, this document will be generated then reviewed by human cardiologists for additional new medications to consider. 

NUTRITIONAL RECOMMENDATIONS except from Standard of Care SSP guidelines

Although daily human caloric needs can be a guide for this species, NRC guidelines were published recently for non-human primates.   A good quality complete food (biscuit) that provides essential nutrients of protein, carbohydrates, fat, vitamins and minerals forms the typical base diet with mixed produce (vegetables, fruit/starches).  Minimal dairy and additional protein sources are considered needed.  Supply of browse is important whenever possible by seasonal availability but may be more enrichment than fiber source for this species.  It is important that all plants used as browse be properly identified as non-toxic species and sources that are not chemically treated.  Toxic plants vary by geographic area and seasonally so texts or specialists should be utilized for the specific facility.  

As complete diets should be balanced for vitamin and minerals, routine supplementation is not expected as necessary although non-human primates have an absolute requirement for vitamin C. (See also Pregnancy Management).  However, human supplement products can be used by label direction; selection of products without excess iron is important unless iron-deficiency anemia is specifically under treatment.   Excessive dietary iron has been associated with hepatic iron storage disease in many exotic species so control of iron intake is advised. 

In juveniles, documented cases of vitamin D deficiency (metabolic bone disease) have occurred in chimpanzees housed exclusively indoors.  Prevention includes routine outdoor access.  When this is not possible due to exhibit design or season, appropriate supplementation with Vitamin D either orally or parenterally as i.m. depot formulation. 

For adults, obesity is a substantial risk factor for cardiac disease and inconsistent with good long-term health.  It is important to include calories obtained from enrichment and operant conditioning sources as part of the balanced diet.  Judicious use of sugar free or low sugar products will assist in maintaining appropriate weight and body condition as well as reduce dental disease.  Regular – several times yearly - weighing is critical to monitoring long-term nutritional maintenance and encouraging weight loss when indicated. 


Standard of Care SSP Veterinary Guidelines was generated and distributed through SSP Steering Committee in 2006. 


Standard of Care SSP Veterinary Guidelines was generated and distributed through SSP Steering Committee in 2006. 


Consultation with Gombe was ongoing on several aspects of medicine this year.  Fecal parasite survey by technical staff at Lincoln Park Zoo has continued. 


None veterinary related but see Chair report for others.


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