Abstract

A 6-yr-old female red ruffed lemur (Varecia variegata rubra) with a 48-hr history of lethargy and anorexia was presented for evaluation of a large cervical mass. A soft fluctuant subcutaneous swelling extending from the dorsal aspect of the skull to the ventral cervical region was present at physical examination. CBC and serum biochemistries were unremarkable at the initial examination. Radiographs of the cervical region showed the mass containing discrete areas of mineralization. Ultrasonography of the mass was non-diagnostic. Surgical exploration of the area revealed a multiloculated mass with each individual cyst-like structure containing hundreds of bead-like nodules (< 1mm). A wet-prep evaluation of the nodules determined that they were cestode larvae. Histopathology of a single mass was described as granulomatous cellulitis with intralesional larval cestodes, a cysticercus. The cestode larvae were identified as Taenia crassiceps. Treatment was initiated with praziquantel (Droncit, Bayer, Shawnee Mission, KS 66201 USA) at 23 mg p.o. q 10 days for three treatments and amoxicillin (Trimox, Bristol-Myers-Squibb, Princeton, NJ 08540 USA) at 95 mg p.o. b.i.d. for 10 days. Albendazole (Valbazen, Pfizer, Exton, PA 08540 USA) at 28.5 mg p.o. b.i.d. was administered for three 10-day treatments with 10-day intervals between each treatment.

Weekly examinations were performed for 2 mo to evaluate response to treatment and to monitor for albendazole-related leucopenia. A 75% reduction in mass size was evident 2 wk after initiation of treatment. Eosinophilia was at this time (1800/µl) and persisted at day 21 (2541/µl). All subsequent CBC and serum biochemistries were unremarkable. At 1 mo post examination the cervical mass was greatly reduced with only minor thickening of the ventral cervical region present. Subsequent examinations at 5 and 7 mo were similar. No further symptoms of the disease have been observed for over 1 yr.

The definitive hosts of Taenia crassiceps are wild, northern hemisphere canids including the grey fox (Urocyon cinereoargenteus) and coyote (Canis latrans). Many wild rodent species serve as intermediate hosts. Cysticercus formation typically occurs in rodents after ingestion of a Taeniid egg. The cestode infestation in this case most likely occurred after ingestion of grey fox feces by the lemur. The enclosure in which this lemur was housed would not allow entry of any animals but it is possible that a fox could have defecated close enough to the enclosure so that the lemur could reach the feces.

Cysticercosis has been reported in other non-rodent species, most recently in immunocompromised domestic dogs^1,4 and humans.³ Cestode infection in lemurs has been primarily reported as a necropsy finding. Hydatid disease due to Echinococcus granulosus was described in ring-tailed lemurs (Lemur catta).⁵ Severe invasive cysticercosis due to Taenia crassiceps infestation was identified at necropsy in a black lemur (Eulemur macaco macaco).² Multiple cysticerci were present within the pleural and peritoneal cavities of this individual. Another report describes the successful surgical excision of a single cysticercus from the thoracic cavity of a red ruffed lemur.⁶ No other treatment was necessary for resolution of the problem and recurrence of the disease was not observed. Species identification of the parasite was not possible.

The cestode infection reported in this particular case was resolved with medical therapy only. Surgical excision of the mass was not possible due to the extensive nature of the cervical mass. Cysticercosis should be considered as a differential diagnosis when evaluating lemurs with subcutaneous swellings. Appropriate hygienic and protective precautions must be taken when managing cases involving Taenia crassiceps due to the potential for zoonotic infection.

References

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