Old World monkeys

Reproductive physiology of the bonnet macaque (M. radiata) has been described. Menarche occurs at around 32 months of age, but there is no obvious "sex skin". Age at first conception is usually 5 years. Gestation is 168 (161-174) days. These macaques breed year-round, with most during the July-October rainy season in India. In the laboratory, housing the animals in humidified (55-65%) rooms prevented "summer amenorrhea". Cycles are much more regular in the laboratory if a male is housed in the same room with the females. Unlike other macaques, bonnet macaques exhibit a cervical mucus discharge from days 8-12 of their 28-day cycle, with ovulation occurring on days 11 or 12. This mucus discharge corresponds to levels of estradiol 17ß of over 200pg/ml. For use in breeding programs, normally cycling females with estradiol 17ß levels of >200pg/ml on days 9-10 become pregnant 80-85% of the time within 3 exposures to a proven fertile male. Females do not cycle during lactation; infants are weaned at 6 months of age.{4018}

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Guenon Physiology

Average weight of adult male Chlorocebus is 7.0 kg, and of females 5.6 kg. Males have a light red penis and a blue scrotum. They eat fruit, cultivated plants, insects, crustaceans, bird eggs and small vertebrates; in some places such as Senegal they hunt for crabs. 

The estrous cycle lasts about 30 days, and gestation is 5½ months. Females usually have young every year. Weaning is completed at 8.5 months of age.{4048}

Macaque Behavior

In the wild, macaques generally live in large groups of up to a couple hundred animals. Females stay in their families, and males stay at the periphery or live in all-male groups. Social status of the young is dependent upon the rank of their mothers.{4048}

Vocalizations include a shrill bark for alarm, barking or screeching in response to aggression, screaming when under attack, a growl of aggression, and a squawk for surprise.{4048}

In laboratory-reared macaques, behavioral testing is commonly performed using the Brazelton Neonatal Assessment Scale, which is discussed in the experimental methodology section.

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Guenon Behavior

Guenons live in large groups with several adults of each sex in the group. The social hierarchy revolves around females. They are territorial, but generally avoid serious conflicts.{4048}

Uses in Research

Obviously, uses of NHPs in research are many and varied. Some specific examples from the recent literature are:

Cercocebus atys, the sooty mangabey, is naturally susceptible to leprosy.{2765} They may be asymptomatic carriers of SIV. Their endangered status complicates extensive use for research.{4163} An article in Nature suggested that human HIV-2 originated in sooty mangabeys (CL Davis 2001).

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Common diseases

Enteric

Enteric disease is the primary cause of morbidity and mortality in colonies, particularly caused by Shigella flexneri, S. sonnei and S. boydii. Clinical signs vary; acute colitis may progress to dysentery (loss of necrotic colonic mucosa), but a more common picture is subacute to chronic diarrhea occurring intermittently. Young animals become carriers. Campylobacter jejuni is another cause of primate diarrhea, particularly in patas monkeys. It may respond to 7-14 days of erythromycin. Salmonella localizes in the ileum, and is less common in primates. Diarrhea, acute deaths and abortion may be caused by Yersinia pseudotuberculosis and Y. enterocolitica, for which wild birds and rodents are reservoirs. Contaminated food may be a source of infection for primates. Cold enrichment of cultures is needed to confirm the presence of the organism. Treatment with chloramphenicol, trimethoprim-sulfa, gentamicin or kanamycin may be effective.{2765}

Acute gastric dilatation (bloat) occasionally occurs. Potential causes include poor husbandry or perhaps an infectious agent such as Clostridium perfringens. Animals in restraint chairs bloat more frequently than those kept in corrals or pens. This is an emergency situation; treatment includes passing a stomach tube and supportive care. Animals recovering from bloat should be placed on a restricted diet for 7-10 days.{2765}

NHPs ingest foreign bodies and may also develop trichobezoars, both of which cause diarrhea, anorexia and weight loss.{2765}

Polychlorinated biphenyls (PCBs) are a component of some concrete sealers. Old World monkeys housed on such concrete surfaces have developed photophobia, palpebral edema, alopecia, gingivitis, periodontitis, diarrhea and emaciation. A characteristic squint is produced by distension of the ducts of the Meibomian glands.{2765}

Respiratory

The second most common cause of morbidity and mortality in primate colonies is respiratory disease (at least it was in 1984!). Pneumonia causes facial cyanosis, and animals sit upright holding onto the cage bars to assist in respiration. Rapid, shallow respiration is observed, with radiographic consolidation. Viral infections such as measles should be ruled out. Bacterial causes include Klebsiella pneumoniae, Streptococcus pneumoniae (which may also cause meningitis), Bordetella bronchiseptica, and Pasteurella multocida.{2765}  

Tetanus causes early signs of depression, dysphagia, stiffening and adduction of the pectoral limbs and a hopping gait. Trismus, piloerection, and extensor rigidity follow; risus sardonicus is the term for facial spasm that leads to flattening of the ears. Death is due to respiratory paralysis. Tetanus antitoxin and treatment of local wounds is essential; routine immunization should be considered, with two doses given 4-12 months apart.{2765}

Tuberculosis poses the most insidious threat to colonies of Old World monkeys. Infection with M. tuberculosis or M. bovis is progressive and usually fatal. It is not a naturally-occurring disease of NHPs, but is contracted from humans. Route of exposure is inhalation. Delayed hypersensitivity, the basis of the intradermal test, takes at least 3 weeks to develop after exposure. A 90-day quarantine with TB testing using mammalian old tuberculin (1500 units, but who assays it?) every 2 weeks is the method of choice for detection. M. avium and related organisms of the MAIS group cause granulomatous enteritis and mesenteric lymphadenitis, although this is rare and sporadic.{2765}

Parasites: In NHPs with diarrhea, large numbers of protozoans are frequently seen, particularly Trichomonas and Giardia. They may be the cause, but are more likely an incidental finding or a sequel to the initial cause. Oral metronidazole (50mg/kg sid x 5-10 days) is helpful. Animals imported from other countries may be infected with malaria. African primates may be infected with a malarial organism called Hepatocystis kochi. Pneumocystis carinii is occasionally found in immunosuppressed macaques with pneumonia. Nematodes such as whipworms (Trichuris) are frequently found in baboons. Strongyloides fulleborni, which can be contracted through ingestion, skin penetration, or autoinfection, can cause serious outbreaks in NHPs. The most common nematode of Old World NHPs, though, is Oesophagostomum. Animals are infected through ingestion, and the larvae penetrate the large intestine producing nodules which rupture. Thiabendazole kills mature worms in the intestine, but not the larvae in the nodules. Anatrichosoma cutaneum is found in the nasal mucosa of the rhesus; usually the infection is inapparent, but cutaneous eruptions may be noticed in the hands, feet and face of cynomolgus monkeys. Finally, the lung mite, Pneumonyssus simicola, is a very common find in wild-caught NHPs, although mild to moderate infestations do not cause severe disease.{2765} 

Fungal: Candida albicans, a skin saprophyte, causes white plaques on the dorsum of the tongue and oral cavity. Coccidioides immitis, found the dry Southwest US, infects animals via spore inhalation and has infected Old World monkeys.{2765}

Viral: Too often viruses that cause no signs of disease in their natural hosts cause fatal outbreaks in other species. Examples from Old World primates and man include Marburg/Ebola, measles, herpesvirus B, simian hemorrhagic fever, yellow fever, and simian varicella virus.{2765}

Any pox-like disease is reportable to the CDC. In Old World monkeys, monkeypox causes outbreaks of high morbidity but low mortality. Yaba in macaques and baboons causes subcutaneous nodules 4-6cm in diameter that resolve spontaneously. OrTeCa pox (BEMP) causes raised nodules .5-1.5cm in diameter involving the epidermis, but not vesiculating. All these are zoonotic.{2765}

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©1999, Janet Becker Rodgers, DVM, MS, DipACLAM, MRCVS

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Comments? Send an email to janet.rodgers@vet.ox.ac.uk