Abstract

Four Leontopithecus chrysomelas (one male, three female golden-headed lion tamarins) and four Saguinus imperator (two male, two female emperor marmosets), belonging to the New World primate colony, Fundação Parque Zoológico de São Paulo, were studied. Table 1 lists the animals according to species, sex, age, origin and necropsy date. The monkeys died from 1991 to 1995. Six animals were found dead without previous clinical signs. A female L. chrysomelas showed extreme apathy, dyspnea and hemoptysis for 1 day prior to death. A male S. imperator presented moderate apathy and dyspnea for a few hours prior to death. All animals were necropsied and specimens from major organs were collected, fixed in 10% buffered formalin, embedded in paraffin, processed routinely for histology, sectioned at 4–6 µm, and stained with hematoxylin and eosin (H&E).

Table 1. Distribution of the affected animals according to species, sex, age,
origin, period on captivity and necropsy date. 1991 to 1994, São Paulo, SP, Brazil.

^aGolden-headed lion tamarin
^bEmperor marmoset

Immunohistochemistry assay for T. gondii was performed on all cases, using a polyclonal antibody to T. gondii (DAKO). The assays were achieved by the streptavidin-biotin-peroxidase method, and the dilution used for the primary antibody was 1:10,000. All individuals exhibited good to regular nutritional condition upon necropsy, and no pathogenic bacteria or fungi were isolated from any case. All animals had pulmonary changes characterized by moderate to severe congestion, edema, hemorrhage and acute to subacute interstitial pneumonia. Other significant lesions reported were discrete to moderate acute necrotizing hepatitis, severe fibrin-hemorrhagic lymphadenitis affecting mainly the mesenteric lymph nodes, necrotizing splenitis and multifocal ulcerative enteritis. In all cases oval to crescent-shaped, 1–6-µm structures compatible with T. gondii were reported. The immunohistochemistry assays confirmed the agent to be T. gondii in all eight cases. The primates of the New World are highly susceptible to toxoplasmosis, rarely surviving after illness. The reason for such phenomenon is unknown. Of eight cases of toxoplasmosis observed in the present report, seven happened without previous clinical signs and the deaths occurred at the same day the animals were seen at hospital. Such a situation is in accordance with previous reports which refer to the fast course of this infection in neotropical primates. The means by which the monkeys were infected remains obscure. Due to age (adult) of seven individuals, the possibility of transplacental infection was rejected for those animals. On a similar basis, all meat supplied to the animals was previously frozen and cooked. Therefore, we believe that the infection was not acquired through ingestion of host tissue cysts. Yet another aspect requiring special attention is the control of access of feral cats to the zoo grounds. In spite of not having been reported, the presence of those animals during the outbreak is a possibility that cannot be completely rejected.

Acknowledgments

This research was supported by FAPESP, grant nos. 95/3621-6 and 97/13970-3.

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