Background and Purpose: Several non-human primate species are used as laboratory animals for various types of studies. Although importation of monkeys may introduce different diseases, special attention has recently been drawn to Marburg and Ebola viruses. This review presented here discusses the potential risk of these viruses for persons working with non-human primates as laboratory animals by focusing on epidemiology, virology, symptoms, pathogenesis, natural reservoir, transmission, quarantine of non-human primates, therapy, and prevention. Conclusion: A total of 23 Marburg and Ebola virus outbreaks causing viral hemorrhagic fever has been reported among humans and monkeys since the first outbreak in Marburg, Germany in 1967. Most of the 1,100 human cases, with nearly 800 deaths, developed in Africa due mainly to direct and intimate contact with infected patients. Few human cases have developed after contact with non-human primates used for various scientific purposes. However, adequate quarantine should be applied to prevent human infections not only due to Marburg and Ebola viruses, but also to other infective agents. By following proper guidelines, the filovirus infection risk for people working with non-human primates during quarantine exists, but is minimal. There seems to be little risk for filovirus infections after an adequate quarantine period. Therefore, non-human primates can be used as laboratory animals, with little risk of filovirus infections, provided adequate precautions are taken.

Background and Purpose: Histopathologic changes, cellular composition, and bacterial spreading were studied in rat spleen after experimentally induced infection with Salmonella typhimurium. Methods: Lewis rats were inoculated intraperitoneally with 10 6 bacteria. Spleen weight, cell numbers, and cell surface markers were studied together with histopathologic changes, and expression of inducible nitric oxide synthase (iNOS). The spread of bacteria to blood, spleen, liver, mesenteric lymph nodes, lung, and kidney was studied at 12 hours, and 1, 3, 7, 14, and 28 days after inoculation. Results: Experimentally induced infection caused an increase in spleen weight and leukocyte numbers, and a decrease in CD49d, on postinoculation days (PID) 3 through 7. Numerous granulomas were disseminated throughout the splenic red pulp also on PID 3 through 7. From PID 14 on, clearance of cellular exudate and regeneration of tissue structure were observed. Massive expression of iNOS was seen on PID 3. Bacterial growth was observed in liver and spleen from 12 hours to 14 days after inoculation. Bacteria were detected in blood on PID 3 and mesenteric lymph nodes were infected from PID 3 through 14. Conclusions: Salmonella typhimurium was rapidly taken up by the reticuloendothelial system. The infection induced weight increase and reversible changes in the spleen, peaking on PID 3 with granuloma formation and infiltration with macrophages. On PID 3, extensive production of iNOS within the granulomas was observed, suggesting initial killing of phagocytosed bacteria, followed by bacterial clearance and tissue regeneration. Cell surface marker expression on CD4+ T cells indicated no change in their numbers; however, there was a time-dependent change in expression of CD49d.

Background and Purpose: Soman, an organophosphorus, anticholinergic, chemical warfare nerve agent, is studied at few research facilities, and there have been few pathologic studies of soman-exposed primates. We describe the brain, heart, and skeletal muscle lesions, review lesions described in literature, and discuss possible pharmacologic mechanisms for soman-induced neuron necrosis. Methods: In this retrospective, histopathologic study, records were obtained for 36 rhesus macaques (Macaca mulatta) that were euthanized 10 days after soman exposure, from a larger group of 103 monkeys that were exposed to soman and used for pharmacologic and lethality studies. Results: Brain lesions were seen in 9 of 15 animals that convulsed and in only 1 of 21 that did not convulse. The brain lesions in our primates were limited to the hippocampus, amygdala, and thalamus (of one animal), and consisted of neuron necrosis and dropout, spongiosis, gliosis, astrocytosis, and vascularization. Heart lesions consisted of myocardial degeneration and necrosis. Three animals had brain and heart lesions, 7 had brain lesions only, and 3 had heart lesions only. Skeletal muscle lesions, although minimal to mild, were in most of the animals, whether they had convulsed, but most had muscular tremors. These lesions were in the biceps brachii (11 of 22 monkeys), anterior tibialis (8/22), biceps femoris (7/22), flexor carpi radialis (5/22), gastrocnemius (3/22), and diaphragm (1/22). The limited literature on soman lesions in primate brain and heart, and the limited information on skeletal muscle lesions, is reviewed. Conclusions: Brain lesions were not as wide-spread as reported in other studies of primates and rodents, and were significantly associated with convulsions. Unlike other studies using rodents, we observed poor correlation between heart and brain lesions; thus, a single hypothesis to explain the pathogenesis for the brain and heart lesions may be difficult to establish.

Background and Purpose: Nonsteroidal anti-inflammatory drugs (NSAIDs) induce gastroduodenal injury and ulceration. The pathogenesis is uncertain, although reductions in cytoprotective prostaglandins and nitric oxide (NO) have been proposed. The effects of several cytoprotective agents on inhibition of gastroduodenal ulcerogenesis induced by CI-987, a novel NSAID, were evaluated in Wistar rats. Methods: Male Wistar rats were given CI-987 orally (PO) at a dosage of 300 or 450 mg/kg of body weight or subcutaneously (SC) (3 x 50 mg/kg), alone or with misoprostol pretreatment (2 x 1 mg/kg, PO). In a second experiment, rats were pre-treated with 2 ml of gelusil PO, 500 mg of sucralfate/kg, PO, 100 mg of ranitidine/kg SC, or 200 mg of N ω-nitro-L-arginine methyl ester (L-NAME)/kg, SC. Duodenal injury was induced by administration of 450 mg of CI-987/kg, PO, 3 x 50 mg of CI-987/kg, SC, or 300 mg of cysteamine/kg, SC. Animals were euthanized within 24 to 48 hours, and the gastrointestinal tract was examined for evidence of gross or microscopic change. Results: The L-NAME significantly reduced the incidence and severity of gastroduodenal injury induced by CI987 and cysteamine. Prostaglandin ameliorated duodenal lesions induced by CI-987 given SC, and Gelusil, ranitidine, and sucralfate were without effect on duodenal lesions induced by NSAID. Conclusions: Preemptive blockade of NO synthase is important in preventing NSAID-induced duodenal injury in rats. Inhibition of cytoprotective prostaglandins and enhanced acid-induced damage are unlikely to be primary mechanisms underlying NSAID-induced duodenal injury in rats.

Background and Purpose: The aim of the study reported here was to investigate the pathomorphologic changes caused by experimentally induced dicroceliosis and their correlation with hepatobiliary function. Methods: Studies were carried out at days 80 and 120 after oral inoculation of hamsters with 40 metacercariae of Dicrocoelium dendriticum. Results: The parasite-induced pathologic changes were assessed by presence of fluke eggs in feces, increased plasma alanine transaminase and aspartate transaminase activities and morphologic alterations. Dicroceliosis was characterized by bile ductular proliferation and enlargement of the bile duct surface area caused by hyperplastic cholangitis in septal bile ducts. The liver from infected animals contained portal tracts infiltrated with small to moderate numbers of lymphocytes, macrophages, and eosinophils. Simultaneously, there was an increase in portal tract collagen that extended to the interlobular septa and caused pressure atrophy of the hepatic parenchyma. The concentration of thiobarbituric acid-reactive substances and the ratio of oxidized to reduced glutathione, measured as markers of oxidative stress, were significantly increased. Conclusions: The presence of oxidative alterations could be related to the morphologic evidence of chronic inflammatory response as well as to liver cellular injury indicated by cellular swelling, and increased presence of peroxisomes and lysosomes.

Background and Purpose: Intranasal challenge of immunocompetent mice with Pasteurella haemolytica results in little or no pulmonary inflammation. The study reported here was designed to investigate the inflammatory response in the lungs of immunodeficient scid/beige mice after similar challenge. Methods: Fifty-five scid/beige mice were challenged intranasally with saline or one of three doses (2.8 x 10⁶, 3.4 x 10⁹, or 3.3 x 10¹¹ colony-forming units [CFU]/ml) of P. haemolytica. The lungs were examined for changes in weight, bacterial count, and presence of gross and microscopic lesions at 24, 48, or 96 hours after challenge. Results: Intranasal challenge with concentrations ≥3.4 x 10⁹ CFU/ml of P. haemolytica induced significantly heavier lung weight, with severe pulmonary lesions, and development of suppurative and fibrinous bronchopneumonia in dose- and time-dependent manner 48 hours after challenge. Pasteurella haemolytica was consistently isolated from the lungs at 24 hours after challenge. Conclusions: Bronchopneumonia was induced by P. haemolytica in mice without manipulation of the mouse or the bacteria. The lesions were similar to those that develop in the lungs of cattle infected with P. haemolytica and indicate potential use of the model for the study of this host/bacterial interaction.

Background and Purpose: Hypothermia and death are used as experimental markers in murine models of staphylococcal enterotoxic shock. This study determined whether body temperature and physical activity, monitored telemetrically, could predict impending death and provide an earlier, more humane experimental endpoint. Methods: The study consisted of two iterations (experiments 1 and 2) to determine reproducibility of the model. Each experiment consisted of 24 BALB/c mice surgically implanted with intra-abdominal telemetry transmitters and then injected intraperitoneally with sublethal or lethal doses of staphylococcal enterotoxin B (SEB) and/or lipopolysaccharide (LPS). Core body temperature and physical activity were continuously monitored in all mice for 10 days before, and 5 days after, injections. Additionally, in experiment 2, subcutaneous temperatures were compared with core body temperatures obtained by telemetry. Results: Body temperature and physical activity were reduced in mice after administration of SEB and LPS, or LPS alone, but not SEB only. There was a significant (P < 0.05) correlation between mortality and body temperature (P = 0.0077), but not physical activity (P = 0.97). Conclusion: Body temperature proved to be an early indicator of mortality in this murine model of staphylococcal enterotoxic shock.

Background and Purpose: The canine intestinal and venous access port (IVAP) model is valuable for investigating hepatic elimination and region-specific intestinal absorption of pharmaceuticals. Previously, long-term functionality of this preparation has been variable. Methods: Catheters of different construction were placed in the proximal and distal portions of the small intestine, colon, and portal vein of subject animals and were attached to separate subcutaneous access ports. Intraoperative, postoperative, and long-term maintenance techniques were developed, modified, and analyzed. Results: Intestinal catheter infections and access site failures were associated with breakdown at the intestinal insertion site. The ileal catheter was prone to obstruction with ingesta. A modified Witzel technique, specialized port-catheter systems, scheduled port-flushing methods, and venous port infection treatment protocols improved the model's longevity. Conclusions: The canine IVAP model is a powerful tool for investigation of regional differences in intestinal absorption and hepatic elimination of drugs. Other researchers can derive increased longevity with the IVAP model by using the technical modifications detailed here: strict sterile technique, closed-end slit-valve catheters, GPV^® ports, the Witzel tunnel technique, routine portal vein infection surveillance, 50% dextrose intestinal catheter infusion, rapid removal of infected intestinal catheters, and critical appraisal of their results. Longevity of the model continues to be improved.

Background and Purpose: Total body scans were performed on 89 domestic cats of various ages, using dual energy x-ray absorptiometry (DEXA) to determine body composition, including fat, lean, and bone mineral content. Bone mineral density results from scans also are presented. Methods: This cross sectional study included data for cats from a closed colony and from privately owned cats. Data were grouped by age and were analyzed by sex and reproductive status to provide information as to the rate of growth of the individual components of body composition. Results: The results indicate that the rate of accretion of bone mineral, fat, and lean tissue differs throughout maturation and by sex. Regressions are provided to highlight age- and sex-related differences. Conclusions: The results of this study emphasize the benefits of examining the growth of each component of body composition when studying the effects of nutrition, disease processes, or therapeutic interventions.

Background and Purpose: Validation of a method for obtaining blood samples that does not change cortisol or prolactin concentrations yet allows serial blood samples to be collected from animals under anesthesia, without prior handling, from freely interacting social groups of small mammals. Methods: Results from five experiments are reported. Male dwarf hamsters (Phodopus spp.) were housed in modified home cages under continuous flow of compressed air that could be switched to isoflurane in O₂ vehicle without approaching the cages. Results: Dwarf hamsters respond to manual restraint with behavioral distress and increase in the concentration of the dominant glucocorticoid, cortisol, and decrease in prolactin concentration. Both effects are evident within one minute. In contrast, when this new method was used, neither cortisol nor prolactin changed in response to repeated sample collection (up to 8 successive samples at 2 hour intervals), prolonged isoflurane exposure, or substantial blood volume reduction (30%). Prolactin concentration was suppressed and cortisol concentration was increased in response to stimuli from other hamsters tested without anesthesia. Suppression of prolactin concentration was graded in response to the degree of stress and equaled the pharmacologic reduction caused by bromocryptine mesylate (50 μg of CB154 x 3 days). Conclusions: The technique is superior to alternatives for studies of behavioral endocrinology of freely interacting small mammals.

Background and Purpose: Spontaneous viral encephalitis is rare in the baboon; yet, during a 13-month period (1993–1994), eight juvenile baboons (Papio cynocephalus spp.) developed acute, progressive nonsuppurative meningoencephalomyelitis caused by an unknown agent. Clinical signs of disease included disorientation and truncal ataxia that rapidly progressed to hemiparesis or paraparesis. Clinicopathologic findings were not remarkable and appreciable gross lesions were not seen at necropsy. Microscopic examination revealed CNS lesions that were characterized by lymphoplasmacytic perivascular cuffing, microglial nodules, demyelination, axonal degeneration, vacuolization, and hemorrhage. Subsequently, a novel syncytium-inducing mammalian orthoreovirus was isolated from the brain tissue of five baboons with clinical signs of infection. Methods: To confirm the etiologic role of the orthoreovirus, two juvenile baboons were inoculated with the virus, then were monitored for 6 weeks. Results: Lesions similar to those seen in spontaneous cases were found in the CNS, and orthoreovirus was isolated from the brain of both animals. Conclusion: Analysis of the outbreak indicated juvenile baboons were most susceptible to disease and the virus had a possible incubation time of 46 to 66 days, but did not indicate a source of the virus or mode of transmission.

Background and Purpose: Episodic phases of continuous poor-quality oocytes obtained from South American Clawed Frogs (Xenopus laevis) often are observed. In publications dealing with the surgical technique of oocyte removal, the frogs' robust constitution and resistance against infections provided by magainins are pointed out. For this reason, clean rather than sterile conditions for the surgical procedure are mostly recommended. However, in most instances, antibiotics are added to the buffer medium when in vitro experiments are performed using oocytes. Methods: After a long phase of poor oocyte quality at our facility, involving oocytes that had been obtained by use of a “clean” surgical procedure, we subsequently cultured oocytes in a buffer medium containing the three antibiotics: penicillin G, gentamicin, and streptomycin. Results: During DNA injection experiments, the oocytes developed black spots on their surface by postoperative day two. Pure culture of the gram-negative non-fermentative rod Pseudomonas fluorescens was obtained from the impaired oocytes; the isolate was resistant to the three antibiotics. By contrast, after aseptic surgical removal and culture of oocytes in buffer medium containing the antibiotics tetracycline and gentamicin, perfect oocytes without bacterial contamination were obtained. Conclusion: Whenever impaired oocyte quality is observed, microbial contamination should be considered as a possible cause.

Background and Purpose: The sexual activity of male tree shrews is socially influenced; therefore, the testicular lesions in adult male tree shrews were of interest. Methods: The testes of 229 adult and 9 subadult male tree shrews were obtained during routine necropsy and were subjected to light microscopy. At one time, 138 animals were experimentally exposed to social conflicts. Results: Hypospermatogenesis (testicular inactivity) was observed in social stress-exposed males up to two years of age. Seasonality of hypospermatogenesis could not be statistically supported. Testicular atrophy, observed in 21 animals, was neither stress- nor age-related; it developed unilaterally, with the left testis preferred. Testicular tumors developed in animals older than 2 years, with increasing frequency particularly of Leydig cell tumors in animals more than fours year old. Conclusion: Testicular lesions were more frequently found in male tree shrews than they were observed in nonhuman primates kept at the German Primate Center. Connections to social stress were statistically supported, particularly with respect to hypospermatogenesis. Testicular tumors, in contrast, were distinctly age related.

Background and Purpose: A recent case study indicated that a hydrocephalic rhesus monkey had abnormal response patterns in a standardized neonatal primate assessment. We conducted a retrospective study to determine whether this assessment could also differentiate neonatal rhesus monkeys that appeared normal but developed signs of hydrocephalus later in life from neonates with normal development and no evidence of hydrocephalus. Methods: One-hundred eighty-two rhesus monkeys were assessed on postnatal days 7, 14, 21, and 30. As neonates, clinical signs of hydrocephalus or other illnesses were not evident in any animal. Six monkeys developed signs of hydrocephalus between 5 months and 5 years of age, and each received confirmed diagnoses of hydrocephalus at necropsy. Results: Compared with colony norms, the monkeys that developed hydrocephalus had diminished orientation abilities, more muscle tension, less behavioral evidence of distress, and more pronounced responses to some reflexevoking stimuli, and difficulty in self-righting (day 7 only). Discriminant function analysis comparing the hydrocephalic animals with a matched control group provided a high probability of correct group assignment at days 7, 14, and 21. Conclusions: Some as yet undetermined factor may predispose some monkeys to develop hydrocephalus, which may also be reflected in different scores on neurodevelopmental test items during early infancy.