Miscellaneous Conditions of Nonhuman Primates

Diabetes mellitus is frequently observed in nonhuman primates in clinical and zoological practice. The genus Cebus is overrepresented. Causes of diabetes vary from obesity (carbohydrate overload), to genetic predisposition, to overall poor dietary choices.

An animal suspected of having diabetes mellitus should be brought to the hospital fasted. Laboratory tests should include CBC, serum biochemical panel, urinalysis, levels of insulin and fructosamine, and glycosylated hemoglobin.

The caretaker should be educated on dietary restrictions and the availability of commercial, species-specific 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 (25–50 mg/kg, PO, every 12–24 hours), as well as parenteral medications such as NPH insulin (0.5 U/kg, SC, every 24 hours) as a starting dose, can be administered.

Insulin glargine has rarely been used to treat diabetes in nonhuman primates, because studies indicate that this drug does not achieve glycemic control in most nonhuman primates with type II diabetes. Because the drug has a potential for complications, such as severe hypoglycemia, its use in nonhuman primates should be limited to animals in research and specialty centers that can be very closely monitored.

For some species, dietary changes with weight loss and calorie restriction can decrease or eliminate the need for medication.

Like dogs, cats, and humans, nonhuman primates are prone to tartar buildup and periodontitis. Periodic examination and teeth cleaning are needed to maintain dental health. Dental radiography should be performed as part of the dental examination. A thorough physical examination should be performed with dental examinations because oral lesions can occur in mild cases of systemic zoonotic diseases such as measles, candidiasis, and streptococcal infections.

When scaling teeth in nonhuman primates, veterinary personnel should wear respiratory and eye protection, especially when working with macaques, which can carry Cercopithecine herpesvirus 1 (Herpesvirus simiae, herpes B virus). Many veterinarians prefer hand scaling over ultrasonic scaling to minimize the potential for aerosolizing the virus, if present, when working with macaques.

Tooth root abscesses are most often due to fracture of a crown, with subsequent exposure of the pulp cavity to bacteria.  Clinical signs include facial swelling, purulent drainage below the eye, nasal discharge, anorexia, and pain on chewing. Diagnosis is confirmed by visualizing tooth root osteolysis radiographically. Several bacteria have been isolated from these lesions; Staphylococcus spp and Streptococcus spp seem to be the most common.

Antimicrobial treatment with amoxicillin (10–30 mg/kg, IM, PO, or SC, every 8–12 hours, for 7–10 days) or amoxicillin clavulanate (10–13 mg/kg, PO, every 8 hours for 7 days) can decrease clinical signs of a tooth root abscess; however, antimicrobials might be inadequate to eliminate the underlying cause.

Extraction of the infected tooth and irrigation of the draining tract might be required. Canine teeth are deeply rooted in nonhuman primates, and alveolar bone removal over the tooth root facilitates extraction. Transection of multiple-rooted teeth into multiple, single-rooted parts also facilitates extraction.

Uncommonly, oral infection with Shigella can result in severe periodontal disease with bleeding gingivitis and loosening of the teeth. Diagnosis is based on oral culture of the affected site. Treatment with dental scaling, extraction of loose teeth, and enrofloxacin (10 mg/kg, PO, every 24 hours for 5 days) is curative.

Oral shigellosis must be differentiated from other causes of gingivitis, including trauma, generalized periodontal disease, and gingivitis associated with tooth eruption in juveniles.

Endometriosis is the presence of ectopic endometrial tissue in the peritoneal cavity. It occurs only in menstruating primates. Clinical signs include abdominal discomfort, slow onset of anorexia and depression in middle-aged or older, female monkeys, a history of menstrual irregularities, infertility, and, occasionally, a palpable mass in the abdomen.

In severe cases of endometriosis, cysts containing dark fluid (chocolate cysts) might be present in the abdominal cavity. These can be visualized directly via laparoscopy or as anechoic cysts via ultrasonography.

Treatment of endometriosis involves ovariectomy with or without removal of the uterus. Medical management to induce a chemical menopause can provide temporary relief; however, it is recommended only for treatment of infertility in endangered species or as a preoperative measure to decrease the risk of bleeding before surgical excision of the ovaries/uterus.

Life-threatening bloat occurs sporadically in captive nonhuman primates and can be associated with feeding after a prolonged fast, periods of water restriction, or accidental overfeeding. Etiological factors include intragastric fermentation associated with Clostridium perfringens and abnormal gastric function.

Nonhuman primates with gastric dilatation become acutely ill, and clinical findings are similar to those in small animals, except that volvulus is less common than in other species.

Acute gastric dilatation in nonhuman primates is often fatal without emergency treatment. The stomach must be evacuated and fluids replaced, in like volume, with electrolyte solution administered parenterally. Shock and dehydration usually occur and require prompt treatment. Periodic evacuation of the stomach might be necessary for several days, until GI function is normal. Metabolic alkalosis can result from continued loss of hydrochloric acid. Adequate sodium, chloride, and potassium must be provided via parenteral fluid therapy.

The number of aged nonhuman primates maintained in captivity has increased over time, primarily because of improvements in husbandry, nutrition, and veterinary care, but also because of an emphasis on animal models for research on aging.

This increase in the aged nonhuman primate population, particularly macaques, has been associated with an increase in the incidence of intestinal adenocarcinoma, which can exceed 20% of animals > 20 years old in some colonies. Intestinal carcinomas are the most commonly reported types of neoplasia in most nonhuman primate species.

Decreased appetite, weight loss, anemia, diarrhea, and a palpable abdominal mass are common clinical findings of intestinal neoplasia in nonhuman primates. Tests for fecal occult blood often yield positive results and should be routinely performed in geriatric animals. Radiography might show changes associated with partial obstruction, and ultrasonography might show an expansive lesion at or near the ileocecocolic junction with or without enlarged lymph nodes, hyperechoic mesenteric fat, or free abdominal fluid. Abdominocentesis and cytological analysis can reveal neoplastic cells within the effusion.

Surgical biopsy is diagnostic for adenocarcinoma. This tumor is most commonly located at the ileocecocolic junction, or, rarely, in the small intestine. Histological lesions include a thickened intestinal wall and constriction of the lumen (“napkin ring” lesions), with variable signs of hemorrhage, ulceration, and advancement of neoplastic cells beyond the basement membrane. Some animals respond favorably to surgical excision with wide margins; however, recurrence is common.

Leiomyoma is the most common benign neoplasm in female nonhuman primates. Although generally subclinical, it can be associated with dysmenorrhea in middle-aged females. Leiomyoma often presents as smooth uterine enlargement on uterine palpation and a clearly defined intrauterine mass on ultrasonography.

Leiomyoma must be differentiated from progressive conditions such as uterine polyps and endometriosis. Diagnosis is achieved via biopsy or cytological analysis of a percutaneous fine-needle aspirate.

Other cancers, such as lymphoma, squamous cell carcinoma, and mammary epithelial carcinoma, are rarely reported in nonhuman primates. Surgical excision of tumors can result in a cure in the absence of further invasive therapy. However, these conditions are often advanced at the time of identification, so complete excision might be unachievable.

Diarrhea is common in nonhuman primates and can occur in the absence of infectious etiologies. Inflammatory bowel disease, food intolerance or concurrent poor diet, or amyloid deposition in organs such as the small and large bowel can contribute to this condition.

Endoscopic intestinal biopsies might be required to definitively diagnose noninfectious causes for persistent diarrhea. Treatment of inflammatory bowel disease or food intolerance should include dietary trials.

In some refractory cases of noninfectious diarrhea in nonhuman primates, probiotics and fiber with immunomodulatory antimicrobials such as tetracycline (20 mg/kg, PO, every 12–24 hours for 7–14 days), sulfasalazine (10–15 mg/kg, PO, every 12 hours for 7–14 days), or tylosin (10–20 mg/kg, PO, every 24 hours for 7–14 days) can assist with resolution of clinical signs. Rarely, prednisone (0.5–1.5 mg/kg, PO, every 12–24 hours for 7–14 days) might be indicated for suspected cases of inflammatory bowel disease.

Trauma resulting from cagemate aggression or self-mutilation (biting or hair pulling) occurs occasionally in nonhuman primates, as does thinning of the hair due to self-induced alopecia. Trauma in captive nonhuman primates is also very commonly observed in clinical practice. Nonhuman primates living in domestic environments might be subjected to wounds inflicted by other animals, such as dogs and cats.

Superficial lacerations and uncomplicated injuries can be treated without antimicrobials. However, analgesia and bandaging are often necessary to ensure normal healing because of the tendency of nonhuman primates to remove sutures or staples.

Massive soft tissue injury in nonhuman primates, such as that from attacks by other animals, can result in acute blood loss and shock, causing coagulopathy and endothelial disruption, with resulting bacterial infections. This complicated chain of events causes hypothermia, acidemia, and inflammation and should be treated as a life-threatening emergency. Rapid control of hemorrhage, correction of hypothermia, early blood component administration, and high-volume fluid therapy are indicated to avert continued ischemia and renal failure. Antimicrobials should be administered to prevent infection and sepsis.

Multimodal pain management—including use of lidocaine (1–2 mg/kg, IV initially, followed by 10–50 mcg/kg/minute, IV CRI) or fentanyl (1–30 mcg/kg, IV CRI), as needed, where indicated—is also necessary for these cases. Gabapentin (10 mg/kg, PO, every 8–12 hours as needed) and acetaminophen (5–10 mg/kg, PO, every 6–8 hours as needed) can also provide analgesia, in combination with opioids.

In cases of severe trauma, renal status and perfusion should be closely monitored before administration of NSAIDs (generally meloxicam at 0.2 mg/kg, PO or SC, once, then 0.1 mg/kg, PO or SC, every 24 hours as needed) to nonhuman primates, because of the risk of acute renal injury associated with myoglobin release.

Group housing opportunities, exercise pens, shelters, foraging activities, and cage toys should be provided to enhance the psychological well-being of nonhuman primates and minimize the chance of trauma caused by aggression. In addition, animals in social groups should be provided facilities for refuge and escape to prevent trauma and decrease the risk of self-injurious behaviors.