Trypanosoma cruzi (Chagas, 1909) transmission among captive wild mammals, triatomines and free-living opossums from surrounding areas in the São Paulo Zoological Park, Brazil

Abstract

Background: Trypanosoma cruzi is a multi-host parasite that infects dozens of mammalian species in the most variable wild environments in Americas. Between 2013 and 2018, autochthonous infections by T. cruzi were suspected in three European wolves (Canis lupus) and an orange dwarf porcupine (Coendou spinosus) from Fundação Parque Zoológico de São Paulo (FPZSP), Brazil, current Coordenadoria de Fauna Silvestre (CFS), which is inserted in a remnant of the Atlantic rainforest inside one of the biggest and most populous municipality of the world. This study aims to detect T. cruzi infections in captive mammals, triatomines and free-living opossums from surrounding areas of FPZSP/CFS.

Methodology/principal findings: Blood samples from captive and free-living mammals from surrounding areas were collected for parasitological (direct examination and culture), serological (IFAT) and molecular diagnosis using Nested-PCR 18SrDNA followed by DNA sequence analysis. Triatomines (Panstrongylus megistus) found in FPZSP/CFS were also examined by culture of the digestive tract and PCR. Trypanosoma cruzi infection was detected in 35.7% (n = 60/168 - 106 captive and 62 free-living) of the mammals that belonged to nine different families. From captive mammals, positive T. cruzi serology was observed in 29.6% (n = 27/91). Twenty-six positive hemocultures were obtained, from which parasite isolation was achieved in 69.2%, while positive PCR was observed in 40% of them, including nine free-living individuals that were also positive in hemoculture. Of 28 individuals in which T. cruzi characterization was successful, 89.3% were genotyped as DTU TcI, 7.2% as TcII and 3.5% as TcI/TcII mixed infection. Besides, 29 of 30 collected triatomines were infected, and infection by T. cruzi DTU TcI was confirmed in 16 of them.

Conclusions/significance: The confirmed autochthonicity of at least 68.9% of cases demonstrates that captive mammals from FPZSP are immersed in the T. cruzi enzootic cycle that involves the vector species P. megistus, and the reservoir hosts C. spinosus and Didelphis aurita from the wild surrounding areas.

Fig 1. Study area located in The Fundação Parque Zoológico de São Paulo (FPZSP), current Coordenadoria de Fauna Silvestre (CFS).

Study area located in São Paulo Zoo, municipality of São Paulo (São Paulo State/Brazil), showing the five transects (A to E) and some of the enclosures of captive mammals, according to the group they were included (I to IV). This map was created using QGIS version 3.28.12 software (EPSG: 4076 - SIRGAS 2000) and cartographic bases maps modified from open access by the Brazilian Institute of Geography and Statistics, IBGE (https://www.ibge.gov.br/geociencias/downloads-geociencias.html).

Fig 2. Quantitative ecological network among captive wild mammals from the FPZSP/CFS and Trypanosoma cruzi.

The bars on the left represent the infected mammals’ species and on the right the protozoan. The frequency of interaction between each species and the protozoan is illustrated by the bars’ length. The links represent the present interactions, and the thickness is proportional to their frequency, represented by distinct colors for each mammalian family.

Fig 3. Phylogenetic tree reconstructed from sequences of the 18S SSU rDNA gene of parasites of the genus Trypanosoma belonging to the T. cruzi clade.

Data originated from: nine captive mammals from the FPZSP/CFS (ex situ), seven free-living mammals (in situ) and seven triatomines. Forty-two nucleotide sequences were used in the analysis, 18 of which were previously published. The numbers include the statistical support values of the inferences, respectively, by the Neighbor-Joining (NJ) (Kimura’s 2-parameter model) and Maximum Likelihood (ML) (Kimura’s 2-parameter model and four-category).