Phylogenetic, morphological and behavioural analyses support host switching of Trypanosoma (Herpetosoma) lewisi from domestic rats to primates

We characterized four Brazilian trypanosomes isolated from domestic rats and three from captive non-human primates that were morphologically similar to T. lewisi, a considered non-pathogenic species restricted to rodents and transmitted by fleas, despite its potential pathogenicity for infants. These isolates were identified as T. lewisi by barcoding using V7V8 SSU rDNA sequences. In inferred phylogenetic trees, all isolates clustered tightly with reference T. lewisi and T. lewisi-like trypanosomes from Europe, Asia and Africa and despite their high sequence conservation formed a homogeneous clade separate from other species of the subgenus T. (Herpetosoma). With the aim of clearly resolving the relationships between the Brazilian isolates from domestic rats and primates, we compared sequences from more polymorphic ITS rDNA. Results corroborated that isolates from Brazilian rats and monkeys were indeed of the same species and quite close to T. lewisi isolates of humans and rats from different geographical regions. Morphology of the monkey isolates and their behaviour in culture and in experimentally infected rats were also compatible with T. lewisi. However, infection with T. lewisi is rare among monkeys. We have examined more than 200 free-ranging and 160 captive monkeys and found only three infected individuals among the monkeys held in captivity. The findings of this work suggest that proximity of monkeys and infected rats and their exposure to infected fleas may be responsible for the host switching of T. lewisi from their natural rodent species to primates. This and previous studies reporting T. lewisi in humans suggest that this trypanosome can cause sporadic and opportunistic flea-borne infection in primates.

Pathology of toxoplasmosis in captive new world primates

Clinical information was available for 32 of 33 New World primates with fatal toxoplasmosis, all of which were subjected to a variable number of pathological observations. Death without apparent clinical signs occurred in 43.7% of cases. The most common clinical findings were malaise (40.6%), dyspnoea (18.7%), hypothermia (15.6%) and a sero-sanguinous or foamy nasal discharge (12.5%). Nutritional status was good in 71.8%, average in 18.7% and poor in 9.4%. The most common post-mortem findings were pulmonary congestion (78.8%), pulmonary oedema (75.8%), splenomegaly (57.6%) and mesenteric lymphadenitis (54.6%). The most common histopathological findings were multifocal necrotic hepatitis (97%), lymphadenitis (95.4%), interstitial pneumonia (90.3%) and necrotic splenitis (71.4%). The gross post-mortem changes in cebids were more variable than those observed in callitrichids, a fact that may complicate the diagnosis of toxoplasmosis in cebids.

Toxoplasmosis in golden-headed lion tamarins (Leontopithecus chrysomelas) and emperor marmosets (Saguinus imperator) in captivity

From 1991 to 1995, eight New World nonhuman primates of the family Callitrichidae belonging to the collection of Fundacão Parque Zoologico de São Paulo died of toxoplasmosis. Of the eight affected nonhuman primates, four were Leontopithecus chrysomelas (one male, three females) and four were Saguinus imperator (two males, two females). The most commonly affected organs were the lungs, liver, and lymph nodes, with hemorrhagic and necrotic lesions. Histopathologic examination revealed protozoa that were morphologically consistent with Toxoplasma gondii. Immunohistochemical assays were strongly positive for T. gondii.