V   Nonhuman Primates

Reading Recommendations:  In-text links.

Study Guide

1. Taxonomy of Nonhuman Primates:
   
   Kingdom Animalia
   Phylum Chordata
   Class Mammalia
   Order Primate

   Suborder Prosimia  (prosimians):                        
        Infraorder Lemuriformes-  Lemurs, Indri, Sifaka and Aye-Aye
        Infraorder Lorisiformes-  Loris, Potto and Galago
        Infraorder Tarsioformes-  Tarsiers  (maybe)

    Suborder Anthropoidea  (simians-  monkeys, apes and humans)-
        Infraorder Platyrrhini  (New World monkeys)
                  Family Callithricidae-  marmoset and tamarin
                  Family Cebidae-  squirrel monkey, spider monkey, etc.
        Infraorder Catarrhini  (Old World monkeys, apes and humans)
             Superfamily Cercopithecoidea  (monkeys)
                  Family Cercopithecidae- macaques, baboons, colobus, etc.
             Superfamily Hominoidea  (apes and humans)
                  Family Hylobatidae-  gibbon 
                  Family Pongidae-  orangutan
                  Family Panidae-  chimpanzee, bonobo and gorilla
                  Family Hominidae-  human

   (Don't panic over all these suborders, infraorders and superfamilies!  DON'T memorize this information.  This taxonomic breakdown is intended to give you an idea of the relationship of the different primates, nonhuman and human.)
   

2. Sources of Nonhuman Primates in Research:

   Traditionally, the nonhuman primates used in research have been wild-caught animals imported into the United States, quarantined for 30 - 90 days and sold to laboratories with minimal conditioning.

   Restrictions on importations in the 1970s and concerns over endangered primate populations led to the establishment of eight  primate centers in the United States for captive breeding of nonhuman primates.  This has reduced laboratory demand on wild nonhuman primate populations.  The centers also coordinate increased sharing of animals in studies to decrease the number of primates needed.  The primary species bred at these centers are rhesus macaques, squirrel monkeys and chimpanzees. 

   Approximately 15,000 wild-caught primates continued to imported into the United States annually.  Most of these are rhesus, cynomologus, squirrel and owl monkeys from the Philippines, China and Peru.

   In December 0f 2000, President Clinton signed the Chimp Sanctuary Bill (Cimpanzee Health Improvement, Maintenance and Protection).  This established a "retirement" facility called Chimp Haven for chimpanzees no longer needed for research.  

3. Role of Nonhuman Primates in Research:

   Nonhuman primates are ideal models for human studies due to similar genetic make-ups: humans are primates (98.7% of our genes are identical).  All primates share many anatomical and physiological characteristics.   Approximately 58,000 nonhuman primates were used in research in 2000:  0.33% of all research animals (and 4% of covered animals).

   Several important advances and uses of primates includes:

   • Study and development of vaccines for infectious diseases such as poliomyelitis, yellow fever, measles, hepatitis A and hepatitis B
   • Malaria research using the owl monkey (malaria kills 2.3 million people annually!)
   • Aging research  (age-related changes in anatomy and physiology, behavior, mental function, Parkinson's disease and Alzheimer's disease)
   • Endometriosis in macaques (uterine tissues are located outside of uterus)
   • Communication  (American sign language acquisition by chimpanzees and gorillas)
   • Rh factor  (Rhesus macaque--mom's antibodies attack offspring)
   • Surgical techniques-
     • Investigation and development of new surgical techniques  (baboons)
     • Removal of  retinal scar tissue leading to macular regeneration.  (this may lead to treatment for human macular degeneration, the leading cause of blindness in  people over 55 years)
   • Transplantation research-
     • Heart transplant surgery  (refined in cynomologous monkey)
     • Baby Fae (first nonhuman heart transplant--baboon--in 1984)
   • Cancer studies-
     • Cell separation technique to remove neoplastic cells from bone marrow without destroying healthy cells in baboons
     • Inflammation in colon of cotton-topped tamarin is similar to lesions in humans that develop into colon cancer
   • HIV studies-
     • Isolation of white blood cells (lymphocytes) that respond to HIV
     • Animal model for AIDS-related dementia
     • Recently an effective HIV vaccine in monkeys has been developed

   There are a number of disadvantages to using nonhuman primates in research.  They are expensive to purchase and maintain.  Their reproductive rate is low (typically one offspring per reproductive cycle) and the developmental period of the young is long.  There are special handling and management requirements, based on the temperament and potentially lethal zoonoses of primates.  In addition, ethical issues on the primates, especially chimpanzees, have limited their use.

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4. Nonhuman Primate Statistics:
   

   Criterion	Nonhuman  Primates*
   Life Span	20 - 30+ years
   Adult Size	200 g to 200 kg
   Temperature	100.6 - 102.6° F
   Pulse	120 - 180 bpm
   Respirations	30 - 40 rpm
   Estrous Cycle	7 - 28 days
   Gestation	150 - 175 days
   Weaning Age	12 - 27 months

*These are representative numbers:  there is considerable variation between the different species of primates.

5. Species Used for Research:

   There are two hundred species of primates comprising four basic groups:  prosimians, Old World monkeys, New World monkeys, and apes.  Approximately thirty species have been used in research, with ten being used most commonly.

   Prosimians are  primitive animals and not widely used in research.  Old World monkeys are the macaques, baboon, patas monkey and vervet (African green) monkey.  New World monkeys commonly used in research are the marmosets and squirrel, spider and owl monkeys.  The chimpanzee is the primary ape used in research.  

   The Old World monkeys belong to Infraorder Catarrhini.  They have downwardly directed nasal openings that are close together.  Their forelimbs shorter than their hind limbs and their palms and soles are naked.  Their tail may be long or vestigial (short), but it is not prehensile (they can't grasp with it or use it for motion).  Many have ischial callosities (hairless areas) or bright-colored skin on their rumps for displays).  All of the Old World monkeys are diurnal and are primarily arboreal, except for baboons.  

   Macaques are found from North Africa to Asia.  The two primary species are widely used in research, the 5 - 10 kilogram rhesus macaque (Macaca mulatta) and the smaller cynomologous or long-tailed macaque (M fascicularis).

   The baboon is Papio.  It is a large African primate with marked sexual dimorphism:  the female weighs 10 - 15 kilograms and the male is twice her size, at 20 - 30 kilograms.  

   The African green or vervet monkey is Cercopithecus aethiops.  It is native to subSaharan Africa and is fairly small (the males weigh 3 - 6 kg and the females 2-4 kg).

   The patas monkey (Erythrocebus patas) is also originates from subSaharan Africa. It is similar in size to the rhesus monkey and it has a more tractable temperament than many of the primates.
   
   Chimpanzees (Pan troglodytes)  are large (to 50 kilograms) apes from equatorial Africa.  These animals are docile when young, but may become aggressive and dangerous after puberty.  Chimpanzees are listed in Appendix I (endangered ) of Convention on International Trade in Endangered Species of Fauna & Flora (CITES) and are not available for importation.  

New World monkeys belong to Infraorder Platyrrhini.  They have flat noses with widely separated outwardly-directed nasal openings.  The tail is prehensile in some species (esp. the spider monkey), allowing them to grasp with their tail and use it for movement.

Marmosets and tamarins are small (300 gram) New World primates.  The common marmoset (Callithrix) is bred in limited numbers in the United States, but is being used more frequently in research projects.  It is used for behavior, neurophysiology and reproductive studies.  Monogamous in wild, it should be pair-housed.

The owl monkey (Aotus) is a nocturnal New World monkey that lives in small family groups.  It is a small (1 kilogram) primate and the only one that is susceptible to Plasmodium falciparum, one of the organisms that causes malaria.  These primates are still available for importation.  

The squirrel monkey is Saimiri sciureus.  It has been used in behavioral studies since the 1930s.  Captive breeding began in the 1940s (although wild-caught squirrel monkeys are available).  Its ease of handling and easy adaptation to the laboratory environment make it useful in research.

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5. Anatomy and Physiology of Nonhuman Primates:

   There are a number of characteristics that are shared by the variety of species of primates.  Most primates are tropical and subtropical.  They vary in size from the 30 gram mouse lemur to the 200 kilogram gorilla.  

   Pentadactylism is a characteristic shared by almost all primates--they have five digits on each foot.  Their fingers (and toes, except in human primates) are prehensile--they can grasp.  They are very flexible and mobile and have flat nails instead of claws on at least some of their digits.  

   They tend toward an erect posture and are occasionally bipedal (two-legged).  The fore and hind legs are very mobile; the clavicles are strong and the shoulder joints are flexible, allowing them to brachiate (use their hands to move from branch to branch).  Their snout size  and the olfactory area of their brain reduced, with concomitant decrease in their ability to smell.  Vision, however, is increased, including depth and color perception.

   Gestation is prolonged and the offspring are somewhat altricial--they are born with open eyes and ears and at least partially furred.  The young remain dependent upon their mothers, however, for an extended period of time.  

   The primate lifespan is fairly long, exceeding forty years in some apes.  Most primates are diurnal, except for the owl monkey, and most are at least partially arboreal (life in trees).  They are highly social, with complex vocalizations and displays, especially grooming rituals.  
   
   Primates are monogastric animals with similar dentition to humans.  Vitamin C and vitamin D supplementation is required

    

7. Nonhuman Primate Reproduction:

   Female primates are continuously or seasonally polyestrous  with an estrous cycle of 7 - 28 days (depending upon the species).  Some Old World species, such as rhesus, baboons and chimps, develop a "sex skin", a reddened, wrinkled appearance to their face and genital area during estrus.  These areas emit sexual pheromones. 

   The male may appear to injure the female during courtship and mating.  This is generally a show of dominance and usually ends without harm.  

The length of gestation varies with the species of primate, but typically is 150 - 175 days long.  This long gestation results in more developed babies and a greater survival rate.  Most primates have single babies; multiple births are rare.  The baby stays with its mother for one to two years.  The material instinct is usually strong and most primates are good mothers, rarely abandoning or mistreating their young.  Occasionally, a female may eat a stillborn baby, but other mothers may carry their dead baby around for days.

Males typically are larger and more aggressive than females.

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8. Nonhuman Primate Temperament:

   Primates are highly social, quick learners and extremely inquisitive.  They have a strong need for contact and communication with others of their species.  Grooming plays an important part of their social lives; individually housed primates are unable to participate in this ritual.  Primates will grab anything within reach, including pens, syringes and lab coats.  

   Some primates are very aggressive toward their caretakers and it is essential to take precautions around them.

9. Nonhuman Primate Technical Procedures:

   The first step in primate handling is proper training due to potential zoonotic diseases and physical danger from the animals.  Primate handlers must use proper restraint, overcome fear, observe safety measures, use good personal hygiene and always wear protective clothing.   

   Prior to beginning work with primates, personnel should be vaccinated for small pox, tetanus, polio, measles and typhoid.  Semiannual injections of gamma globulin should be administered to protect against infectious hepatitis.  All personnel should be tested for tuberculosis.  Serum should be collected and stored for potential diagnostic comparison if disease is suspected.  Protective clothing includes masks, eye and face shields, heavy leather gloves, caps and gowns.  Strict personal hygiene must be practiced:  personnel must shower and completely change clothes, including shoes, when entering and exiting the primate facility.  

   Primates are very strong and may be difficult to handle.  Restraint can be accomplished by using squeeze cages, with movable panels that decrease cage size, restricting the movement of the primate.  Restraint collars and poles are similar to collars and leashes used with dogs, except that the pole is inflexible and allows you to hold the primate away from your body.  Manual restraint may be used on primates smaller than ten kilograms, by holding the animal's forearms behind its back and extending the hind legs firmly forward.  

The federal Office of Laboratory Animal Welfare has an on-line tutorial on "Working Safely With Nonhuman Primates."  

Tattoos, collars and subcutaneous transponders can be used for identification.

Blood can be collected from the cephalic, femoral, saphenous and jugular veins.

8. Nonhuman Primate Husbandry:

   Primates should be housed in  group cages if possible.  If primates are individually caged, they must be in visual contact with other primates.  It may be necessary to use solid cage sides or ensure that the cages are far enough apart so that primates can't reach into another's cage.  Cage size depends on species, age and research needs.    Cages should have locks that primates can't open.  Slotted floors allow urine and feces to drop through.

   Primates are extremely dirty and will throw food and feces at their caretakers and at each other.  A smooth hard finish to the floor, walls and ceiling are important characteristic of the primate room.  Epoxy resins on the floor and walls provide a good biological seal, are easily cleaned and very durable.  Fixtures should be flush with the walls and ceilings.  Exposed water pipes may be pulled down by playing primates.  The optimal temperature for most primates is 70 - 78° F and humidity should be 40 - 60%.  

   Most primates are vocal and hearing protectors may be needed when working in a primate room.

   Environmental enrichments are essential to a primate's well-being (and required by federal law!).  Enrichments can include resting perches, nesting boxes, foraging boards (carpeted boards with seeds embedded in the pile), swings and balls.   
    

   Most primates are omnivores and some are strict herbivores.  In the laboratory, commercial monkey chow with supplemental vitamins C and D is fed along with fresh fruits and vegetables.

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9. Nonhuman Primate Health and Disease:

   Primates are susceptible to many diseases, including some potentially lethal zoonotic viruses.  It is essential to be aware of the possible threats to you and the animals in your care.  

   Bacteria such as Escherichia coli, Salmonella, Campylobacter and Shigella may cause severe diarrhea in any animal, including human and nonhuman primates.  Proper husbandry procedures, including sanitation, help prevent disease associated with these bacteria.

   All primates, including man, are susceptible to tuberculosis (TB).  Primates should be tested upon arrival at the animal facility and every two weeks until three consecutive negative tests occur, and quarterly retesting is recommended.  Personnel working with primates should have semiannual TB skin tests.

   Of particular importance due to zoonotic infections are the viruses that may be present in primates, some of which cause inapparent  or subclinical infections in primates, but severe clinical disease in humans.

   Cercopithecine herpesvirus 1 (herpesvirus B) should be assumed to be present in all primates, especially macaques (which rarely exhibit clinical signs).  Transmission can occur through saliva (from bites or contamination of superficial wounds) and other body fluids.  In general, signs in nonhuman primates are limited to cold sore-like lesions; however, fatal encephalitis has occurred in primate handlers.

   Hemorrhagic fevers, such as Ebola and Marburg, occurs in primates and may be transmitted to man.  These diseases are associated high fever, epistaxis (nose bleeds), ecchymoses (bruising), bleeding into the gastrointestinal tract and other organs, hypotension due to blood loss and death. 

   Nonhuman primates can also acquire infections from humans, such as measles, influenza and tuberculosis and care must be taken to prevent this transmission.