Miscellaneous Conditions of Nonhuman Primates
Diabetes is frequently seen in nonhuman primates in clinical and zoological practice. The genus Cebus is over-represented. Causes of diabetes vary from obesity (carbohydrate overload), genetic predisposition, and overall poor dietary choices. The animal should be brought to the hospital fasting; laboratory tests should include a CBC, serum chemistries, a urinalysis, levels of insulin and fructosamine, and a glycosylated hemoglobin. The caretaker should be educated on dietary restrictions and the availability of newer commercial diets for these animals. Blood glucose readings can be obtained at the facility or at home by the caretaker, and oral medications such as metformin 5–10 mg/kg, PO, twice daily. as well as parenteral medications such as NPH insulin at ½ unit/kg, SC, daily, as a starting dose can be administered.
Life-threatening bloat occurs sporadically in captive nonhuman primates and may be associated with feeding after a prolonged fast or periods of water restriction or accidental overfeeding. Etiologic factors include intragastric fermentation associated with Clostridium perfringens and abnormal gastric function. Monkeys become acutely ill, with clinical findings similar to those seen in small animals (see Gastric Dilation and Volvulus in Small Animals). Acute gastric dilatation is often fatal without emergency treatment. The stomach must be evacuated and fluids replaced, in like volume, with electrolyte solution given parenterally. Shock and dehydration usually occur and require prompt treatment. Periodic evacuation of the stomach may be necessary for several days until GI function is normal. Metabolic alkalosis may result from continued loss of hydrochloric acid. Adequate sodium, chloride, and potassium must be provided via parenteral fluid therapy.
Infection with Clostridium tetani is a risk with free-ranging and outdoor-housed monkeys, particularly as a consequence of fighting, parturition, frostbite, and other forms of skin trauma. Immunization with tetanus toxoid should be considered for populations at risk. Marmosets are routinely vaccinated with adsorbed human product or equine product at 0.25 mg, IM, every 5 years. (Also see Tetanus.)
The number of aged nonhuman primates maintained in captivity has increased in recent years, primarily due to improvements in husbandry, nutrition, and veterinary care, but also because of an emphasis on animal models for aging research. This increase in the aged nonhuman primate population, particularly macaques, has been associated with an increase in the incidence of intestinal adenocarcinoma, which may exceed 20% in animals >30 years old in some colonies.
Decreased appetite, weight loss, anemia, and a palpable abdominal mass are common clinical findings. Tests for fecal occult blood are often positive. Radiographic examination may show changes associated with partial obstruction. Surgical biopsy is diagnostic for adenocarcinoma. The location of these tumors is most commonly the ileocecocolic junction, rarely in the small intestine. Histologic lesions include a thickened intestinal wall and constriction of the lumen (so-called “napkin ring” lesion), with variable signs of hemorrhage and ulceration. Metastatic lesions are uncommon, and some animals respond favorably to surgical excision.
Trauma from cagemate aggression or self-mutilation (biting or hair pulling) may occur occasionally, as may thinning of the hair due to self-induced alopecia. Trauma in captive nonhuman primates is also very commonly seen in clinical practice. Animals that live with other species in the domestic environment may be subjected to wounds inflicted by dogs and cats. Massive soft-tissue injury, such as that which occurs from these attacks, may cause increased loads of bacteria into the bloodstream, as well as acute blood loss and shock, causing coagulopathy and endothelial disruption. This complicated chain of events causes hypothermia, acidemia, and inflammation and should be treated as a life-threatening emergency. Rapid control of hemorrhage, correcting the hypothermia, early blood component administration, and high-volume fluid therapy are indicated to avert continued ischemia and renal shutdown; antibiotics should be given to prevent infection and sepsis.
Measures should be taken to enhance the psychologic well-being of nonhuman primates (eg, group housing, exercise pens, shelters, foraging activities, and cage toys; see Psychological Well-being and Environmental Enrichment of Nonhuman Primates), and animals in social groups should also be provided facilities for refuge and escape.