Abstract. Only one case of infection by tetrathyridia larvae ofthe tapeworm genus Mesocestoides was detected in 4 16 necropsies ofcaptive vervet monkeys (Cercopithecusaethiops). Two hundred nine larvae were distributed between both pleural cavities. Mass and size ranges of larvae were determined. A plasma cell reaction indicated a humoral immune response to parasite antigens, which may have contributed to acute, lethal cardiac shock.Coagulative myocytolysis was confirmed. The history of this case and associated circumstantial evidence and reports in the literature suggest that infection of primates by tetrathyridia probably occurs after capture rather than before.Key words: Adrenaline; African Green monkeys; cockroaches; contraction bands; tapeworms; tetrathyridia; thyroid.Vervet monkeys (Cercopithecus aethiops) are called African green monkeys in the United States. An adult female trapped near the Orange River in the Cape Province of South Africa late in 1983 weighed 4.2 kg, which is heavy for a wild female. During the subsequent 6 years and 3 months in a closed indoor facility, she became obese, with a maximum weight of 5.38 kg. Clinically, she was apparently healthy, except that she seemed to be infertile after rearing one infant. She died unexpectedly without prodromal signs. At 8:00 a m . , her habitus, appetite, and feces were normal. At 1200 p.m., she was dead with no visible indications of the cause. The relaxed cadaver was warm and weighed 5.24 kg. The interim was estimated at up to 1 hour. Necropsy was performed immediately.Two hundred nine parasites were evenly distributed between the pleural spaces, lying free in serous fluid containing strands of fibrin. The parasites were soft, pliable, creamy white in color, elongated, and flattened. Slow, spontaneous body ripples indicated they were viable. Based on their anatomy and occurrence free, not in cysts, the parasites were identified as tetrathyridia larvae of the genus Mesocestoides.Parasites from both pleural cavities were weighed, measured and fixed in 10% buffered formalin (pH 7.2). The liver, heart, kidneys, brain, and spinal cord of the monkey were sliced at approximately 5-mm intervals to facilitate penetration by formalin after immersion. The lungs were filled with formalin via the trachea. Tissues and parasites were prepared for light microscopy by standard methods. To detect effects of migrating parasites on tissues, multiple sections were prepared of lung (102), ventricular myocardium (68), arteries (32), and the central nervous system (95). All sections were stained with hematoxylin and eosin (HE). Von Kossa stain and reticulin stain were applied to selected sections. Fresh organ weights were compared with those from nonobese healthy contemporary adult females in the same environment, thereby establishing gland : somatic tissue ratios for vervets (Table 1). Chemical pathology, hematology, thyroid functions, and plasma lipid records of the affected monkey were reviewed for possible effects of the parasites.The average weight per parasite ( n ...
