Abstract

A young-adult male squirrel monkey (Saimiri sciureus) presented with a 1-wk history of anorexia, weakness, wasting, diarrhea and vomiting. Upon admission, it was dehydrated, postrated and had diarrhea with blood, generalized muscle atrophy and pale mucous membranes. The haircoat was dry and dull and there was focal hypotrichosis in the tail and hindlimbs. The animal was stabilized with lactated Ringer’s (i.v. and s.c.), enrofloxacin (5 mg/kg i.m., s.i.d., 7 days; Baytril® 2,5%, Bayer, Leverkusen, Germany) and dexamethasone (1.75 mg/kg i.m.; Resdex, Schering-Plough, Segré, France). A direct fecal revealed eggs similar to those of Strongyloides; the animal was treated with ivermectin (200 µg/kg s.c.; Ivomec®, Merck Sharp & Dohme BV, Haarlem, The Netherlands) within 18 hr. Fat-soluble vitamins (5,000 IU A, 1,250 IU D₃ and 25 IU E, i.m.; Veterín-Vit A+D₃+E®, Hoechst-Roussel, Barcelona, Spain) and B-complex vitamins (10 µg B₁₂, 5 mg B₆ and 2.5 mg B₁, i.m.; Hidroxil® B₁₂-B₆-B₁, Laboratorios Almirall, Barcelona, Spain) were administered on days 0 and 5 respectively. From day 0 fluid therapy was furthered with an oral energetic product containing water-soluble vitamins and minerals (Pet Energy Punch, PER®, Boaz, AL) that the animal began to drink voluntarily from day 4. It recovered from shock and started urinating within 16 hr of presentation. Blood disappeared grossly from feces (day 0) and diarrhea stopped on day 3; culture of a rectal swab was negative for enteropathogenic bacteria (day 1). Hematology revealed prominent elevations of CPK, ALT, and LDH, consistent with muscular damage, elevated amylase and lipase, hypercalcemia with normal phosphorus and AlkP, and mild hypoalbuminemia and azotemia. On day 5, azotemia worsened despite rehydration and there was a 3.8- and 2.8-fold rise in amylase and lipase respectively; hypoalbuminemia was more prominent and calcium dropped slightly below normal. Vitamin E (13 mg/kg i.m.) and selenium (0.14 mg/kg i.m.) (Vitasel, Laboratorios Ovejero, León, Spain) were administered based on a presumptive diagnosis of nutritional myopathy (day 5). On days 2–6 the animal was fed a high protein, high fat mix (Nutribird A19, Prestige Products NV Versele-Laga, Denze, Belgium) despite weakness and impaired deglutition. On day 6, it developed cardiorespiratory arrest and died; blood was collected and serum frozen at −80ºC.

At necropsy, generalized muscular atrophy was in contrast with moderately abundant fat stores. The pancreas had white nodules up to 3 mm in diameter. The tongue had well-demarcated reddish swollen areas on cut surfaces. A complete set of tissues was preserved in 10% buffered formalin and routinely processed for histology; special stains on selected tissues included periodic acid Schiff (PAS), Ziehl-Neelsen (ZN), Gram, von Kossa, Warthin-Starry, Perls’ iron and Congo red. Liver and hair were frozen at −20°C.

Lesions of chronic pancreatitis (CP) consisted of acinar and ductal dilatations by plugs, ductal hyperplasia and mucous metaplasia, acinar atrophy and degeneration, fibrosis, lymphocytic infiltrates, and granulomatous and necrotizing pancreatic steatitis. There was diffuse degeneration of gastric glands associated with chronic lymphocytic gastritis and no spiral bacteria. Chronic degenerative myopathy (DM) with dystrophic mineralization was generalized but most pronounced in limb and tongue muscles. The skeletal fibers in the esophagus had vacuoles containing von Kossa- and ZN-negative, PAS-positive basophilic material. The tongue had two other lesions: fungal pseudomembranous superficial glossitis and bacterial necrotizing glossitis. The heart had diffuse lipofuscinosis. A ZN-negative, PAS-positive, finely granular intracytoplasmic material was seen in adipocytes (brown fat), and cardiac and tongue myocytes. In the kidneys, distal and collector tubules contained casts of a finely granular to fibrillar eosinophilic material, most likely myoglobin; the epithelium of affected tubuli usually had prominent intracellular edema or was flattened. The testes had early atrophy and degeneration (presence of multinucleate giant spermatids, almost complete absence of tailed spermatids, and predominance of Sertoli’s cells and primary spermatids).

Vitamins E and A, and selenium determinations were done on serum collected at the time of death; hair was tested for zinc and liver for selenium. Vitamins E and A were determined by high performance liquid chromatography, whereas flame and hydride-generation atomic absorption spectrophotometry were employed for zinc and selenium analyses respectively. Serum vitamin E levels (0.0092 µg/ml) were extremely low; most primates range 5–20 µg/ml^7,13 (E. Dierenfeld, personal communication); hepatic selenium (<0.1 ppm) and hair zinc (171 μg/g) levels were low.^8,12 Vitamin A was at 6 µg/dl, that may also be deficient.^13,23

CP is thought to have played a major role in the wasting syndrome associated with DM and apparent deficiency of multiple antioxidants in this animal. Morphologically, the pancreatic lesions are reminiscent of chronic calcifying pancreatitis (CCP) of man, that is characterized by the formation of pancreatic calculi sometime during the disease.^4,17 However, some findings (acinar plugs and ductal hyperplasia) are not expected in CCP and have been described in children with kwashiorkor, a form of protein-calorie malnutrition (PCM) that causes pancreatic acinar atrophy,² after refeeding with a balanced diet; together with ductal plugs and fibrosis, these lesions have been considered a possible transitional form between the pancreatic lesions of PCM and those of CCP.¹⁵ It is not possible to rule out underlying PCM in this squirrel monkey as its hematologic and histologic diagnostic features may have been masked, if present, by CP and the other diseases found. In man, possible causes of CCP include a low fat and protein diet, antioxidant deficiencies, hypercalcemia, and alcoholism coupled with a high fat and protein diet;^4,5,17,19 despite some associations with PCM,^5,15 PCM alone does not seem to be a cause of CCP.¹⁸ Despite normal calcemia on day 5, the cause of initial hypercalcemia associated with mild hypoalbuminemia is unknown and may have been involved in the development of CP. The etiology of CP in this squirrel monkey may be multifactorial and the lack of knowledge on its diet precludes further discussion on possible nutritional causes. Trichospirura leptostoma, the spirurid nematode commonly found in the pancreatic ducts of New World primates, seems to have little impact on their health but can be associated with CP;^16,22 T. leptostoma was found in a colony of common marmosets with wasting, apparent malabsorption and CP.¹⁶ T. leptostoma was not found in 75 sections from seven different areas in the pancreas of this squirrel monkey.

In man, fat-soluble vitamin deficiencies are common in CP as a result of steatorrhea and inappropriate nutrition.^9,19,23 This animal was apparently deficient in multiple antioxidants, including vitamin E, selenium, zinc and probably vitamin A. In humans, deficiency of multiple antioxidants has been well documented in CP,^19,23 and may be involved in its pathogenesis.¹⁹ Elevations of CPK, LDH and ALT, vitamin E deficiency and apparent selenium deficiency correlated well with DM. Whenever DM is suspected panels of CPK, LDH, ALT and AST should be selected for their higher sensitivity and specificity for the diagnosis of DM.⁶ DM in vitamin E-deficient primates has been described,^1,3,7,11,13 and the disease has been associated with wasting and pancreatic acinar atrophy in callitrichids.^1,3 In this squirrel monkey, it is reasonable to assume that CP caused malabsorption/maldigestion associated with a primary and/or secondary deficiency of multiple antioxidants, that may have been involved in the pancreatic lesions, DM, dermatosis and testicular atrophy. PCM and antioxidant deficiencies should be considered in the differential diagnosis of reproductive failure in primates.

Initially, azotemia was mild and apparently prerenal; however, after rehydration there was a 2.8-fold rise in BUN and a lesser increase of creatinine that were attributed to myoglobinemic nephrosis. DM may have also increased creatinine per se. Hyperamylasemia and hyperlipasemia may correlate with azotemia and/or pancreatic and gastric lesions; however, on day 5, amylase and lipase values were 5.7 and 4.8 times greater than the upper limit of normal, respectively, which is unlikely to result from renal dysfunction alone.

Both candidiasis and bacterial necrotizing glossitis strongly suggest a poor immunologic status and should not be considered unusual complications in debilitated or hospitalized primates treated with antibiotics or corticosteroids or otherwise immunocompromised. Antioxidants play a major role in immunity;^10,14,20 vitamin E levels correlate positively with positive delayed-type hypersensitivity to Candida,¹⁴ the candidacidal activity by neutrophils is reduced during selenium deficiency,¹⁰ and reduced macrophage phagocytosis of Candida occurs in zinc deficiency.²⁰ Thus, candidiasis (and perhaps bacterial glossitis) were probably the result of a breakdown in the antioxidant system of this squirrel monkey.

Acknowledgments

ISIS blood reference values for squirrel monkeys were gently provided by Dr. Roberto Aguilar, Audobon Zoological Gardens, New Orleans, LA. This report is part of a prospective study on wasting syndromes and antioxidant deficiencies of New World primates that is supported by Laboratorio de Diagnóstico General, Universitat Autònoma de Barcelona, and Clínica Exòtics (Barcelona, Spain).

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