Signalment:  

12-year-old male ring-tailed lemur (Lemur catta)This captive ring-tailed lemur was housed in a Midwestern American zoo and first presented with labored breathing and was immobilized for a physical examination. It had significant respiratory effort under anesthesia. A large mass was observed on a thoracic radiograph, obscuring the heart shadow. The lemur recovered from anesthesia but continued to have labored breathing and lethargy. It was humanely euthanized.

Gross Description:  

A 9 x 7 x 9 cm gelatinous mass was present in the pleural cavity, replacing and displacing most normal lung parenchyma.

Histopathologic Description:

The lung tissue is largely replaced in many sections by large thickwalled fibrous cavities with adjacent and intramural abundant lymphoplasmacytic nodular aggregates of macrophages, neutrophils, and eosinophils. The cavities are often lined by activated macrophages. Within many cavities are large, often multiple, viable and degenerate larval cestodes characterized by their segmented integument, calcareous corpuscles, a scolex with a rostellum bearing hooklets, and spinous tegument. Exogenous budding from the end opposite the scolex is present in some slides. In the remaining lung, there were multifocal areas of parenchymal collapse of airways, peripheral emphysema, and pools of neutrophils, fibrin, and hemosiderin-laden macrophages in alveolar spaces and within capillaries. Many megakaryocytes were also circulating in the capillaries.

Small nodular areas of lymphoplasmacytic inflammation are noted on the serosa of the intestine and on the diaphragm.

Morphologic Diagnosis:  

Lung: Severe granulomatous and fibrous pleuropneumonia with intralesional larval cestodes (presumptive Cysticercus longicollis, the larval form of Taenia crassiceps)

Condition:  

Cysticercus longicollis

Contributor Comment:  

Larval cestodes often present as cysts, of which there are several forms: cysticercoids, cysticercus, coenurus, and hydatid cyst.(3) Of these, the presented case is a cysticercus based on the presence of only one scolex in each bladder (though bladder walls have degenerated in many of the fibrous cavities). Other key features to note are the thick tegument and the deeply basophilic calcareous corpuscles which are most numerous on the neck and scolex, but not in the bladder wall.(3)

Pulmonary, pleural, or peritoneal infection of lemurs by cysticerci has been well documented anecdotally and in the literature.(2,4) Based on these reports, one of which included molecular confirmation, and the similar morphology including rare budding seen in this case, the most likely etiology is Cysticercus longicollis, the larval form of Taenia crassiceps, though other Taenia sp. are possible.

Exposure to feces of the definitive host (typically wild canids, but also domestic cats and dogs) or consumption of infected secondary rodent hosts are possible modes of transmission to the lemur in this case. After ingestion by an aberrant host, it is not well-documented as to how the cysticerci migrate to the peritoneal or pleural cavities, but once there, these cases can be remarkably fulminating since the organism can proliferate by budding both endogenously and exogenously. Infection and rapid proliferation is associated particularly with immunosuppression. This disease is zoonotic, most recently associated with AIDS patients. There was no history or clinical pathology data to suggest this lemur is immunocompromised, but the perceived high frequency of cysticercosis in lemurs might indicate a predisposition in this exotic species which has presumably never been exposed to canid or felid parasites in their evolutionary history until very recently.

JPC Diagnosis:  

Lung: Cysticerci, multiple, with fibrosis and mild histiocytic and eosinophilic pneumonia.

Conference Comment:  

There is some variation among slides, and some participants may have received two sections of lung in which the histiocytic and eosinophilic pneumonia and bronchitis are a more prominent feature due to the presence of larval cysticerci in airways.

Other important cysticerci in veterinary species are as follows(1):

ADULT TAPEWORM	DEFINITIVE HOST	LARVAL FORM	INTERMEDIATE HOST	SITE
Taenia saginata	man	Cysticercus bovis	cattle	muscle
Taenia solium	man	Cysticercus cellulosae	pig, man	muscle
Taenia(Multiceps) multiceps	dog	Coenurus cerebralis	sheep, cattle	CNS
Taenia hydatigena	dog	Cysticercus tenuicollis	sheep, cattle, pig	peritoneum
Taenia ovis	dog	Cysticercus ovis	sheep	muscle
Taenia pisiformis	dog	Cysticercus pisiformis	rabbit	peritoneum, liver
Taenia serialis	dog	Coenurus serialis	rabbit	connective tissue
Taenia taeniaeformis	cat	Cysticercus fasciolaris (strobilocercus)	mouse, rat	liver
Taenia krabbei	dog	Cysticercus tarandi	reindeer	muscle
Taenia mustelae	wild felids		rodents	liver
Diphyllobothrium latum	bear, man		fish	muscle
Diphyllobothrium pacificum	seal, sea lion		marine birds	muscle

References:

1. Bowman DD, Lynn RC, Eberhard ML. Georgi's Parasitology for Veterinarian. 8th ed. St. Louis, MO: Saunders; 2003:130-153, 269, 275, 375-7
2. Dyer NW, Greve JH: Severe Cysticercus longicollis cysticercosis in a black lemur (Eulemur macaco macaco). J Vet Diagn Invest 10: 362-364, 1998
3. Gardiner CH, Poynton SL: An atlas of metazoan parasites in animal tissues Armed Forces Institute of Pathology, Washington, D.C., 2006
4. Luzon M, de la Fuente-Lopez C, Martinez-Nevado E, Fernandez-Moran J, Ponce-Gordo F: Taenia crassiceps cysticercosis in a ring-tailed lemur (Lemur cata). J Zoo Wildl Med 41: 327-330, 2010

Click the slide to view.

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4-1. Lung

4-2. Lung

4-3. Lung

4.4 Lung

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